WO2002014261A2

WO2002014261A2 - 4-substituted d-glutamic acid derivatives for use as antibiotic

Info

Publication number: WO2002014261A2
Application number: PCT/US2001/022589
Authority: WO
Inventors: Alfonso De Dios; Jesus Ezquerra-Carrera; James Eugene Mcgee; Jose Alfredo Martin; Lourdes Prieto; Almudena Rubio-Esteban; Michele Ceceil Smith; Mark Joseph Tebbe
Original assignee: Eli Lilly and Co
Current assignee: Eli Lilly and Co
Priority date: 2000-08-10
Filing date: 2001-08-09
Publication date: 2002-02-21
Anticipated expiration: 2003-02-10
Also published as: WO2002014261A3; AU2001278945A1

Abstract

Compounds of general formula (I), in which: X represents a bond, O, S, SO or SO2; and R1 represents a (1-10C)alkyl, (2-10C)alkenyl, (2-10C)alkynyl, (4-10C)alkadienyl, carboxamido(1-8C)alkyl or aminocarbonyl(1-8C)alkyl group which is unsubstituted or substituted by (3-10C)cycloalkyl or by one or two unsubstituted or substituted aromatic groups, or an ester or amide thereof, or a salt thereof are inhibitors of glutamate racemase and are useful as antibiotics.

Description

CHEMICAL COMPOUNDS

The present invention relates to chemical compounds . More particularly it relates to novel D-glutamic acid derivatives, to pharmaceutical compositions comprising D- glutamic acid derivatives, to use of D-glutamic acid derivatives as antibiotics and to a process for preparing D- glutamic acid derivatives .

Resistance to the presently available antibiotics is becoming an increasingly serious problem. There is ^■ therefore a need for antibiotics that work by new mechanisms .

Glavas S., and Tanner M. E., Bioorganic and Medicinal Chemistry Letters, Vol. 7, No. 17, pp 2265-2270, 1997 discloses that D-N-hydroxyglutamate is a competitive inhibitor of glutamate racemase (Murl) , -an enzyme which is involved in the synthesis of the bacterial cell wall. The authors disclose that the compound acts as a substrate for the enzyme, instead of L-glutamate, and is converted by the enzyme into -ketoglutarate and ammonia.

It has now been found that certain 4-substituted D- glutamic acid derivatives without an N-hydroxy group are inhibitors of glutamate racemase and possess antibiotic activity. Glutamic acid possesses a center of asymmetry and may therefore exist in racemic form, or in the enantiomerically pure D- and L-forms.

Certain 4-substituted glutamic acid derivatives are known in the literature, mostly in racemic or L-form, as glutamate receptor modulators, useful in the treatment of disorders of the central nervous system. References disclosing these compounds include United States patents numbers 5,589,501 and 5,576,323 and European patent application publication number EP-A2-0826663. United States patent number 5,589,501 also discloses 4-substituted glutamic acid derivatives having as the 4-substituent a 3- phenyl-2-propenyl, 3- (4-chlorophenyl) -2-propenyl, 4- fluorobenzyl or 1-naphthylmethyl group.

As described hereinabove, certain 4-substituted D- glutamic acid derivatives have been found to be inhibitors of glutamate racemase.

According to one aspect, therefore, the present invention provides the use of a compound of general formula

I in which: X represents a bond, 0, S, SO or S0₂; and

R¹ represents a (1-lOC) alkyl, (2-10C) alkenyl, (2- 10C)alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for use as a glutamate racemase inhibitor.

According to another aspect, the present invention provides a method of inhibiting glutamate racemase in a patient requiring such treatment, which comprises administering an effective amount of a compound of formula I, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof as defined hereinabove. Compounds of formula I have also been found to possess antibiotic activity. According to another aspect therefore, the present invention provides of a compound of general formula I, a pharmaceutically acceptable metabolically labile. ester or amide thereof, or a pharmaceutically acceptable salt thereof as defined hereinabove for the manufacture of an antibiotic medicament .

According to yet another aspect, the present invention provides a method of combating a bacterial infection in an animal in need of treatment, which comprises administering to said animal an effective amount of compound of general formula I, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof as defined hereinabove.

Many of the compounds of formula I are believed to be novel and are provided as a further aspect of the invention.

Accordingly, the present invention provides a compound of general formula

I in which:

X represents a bond, 0, S, SO or S0₂; and

R¹ represents a (1-lOC) alkyl, (2-10C) alkenyl, (2-

10C) alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, or an ester or amide thereof, or a salt thereof, provided that when X represents a bond, R¹ cannot represent a 3-phenyl-2- propenyl, 3- (4-chlorophenyl) -2-propenyl, 4-fluorobenzyl or 1-naphthylmethyl group. Compounds according to the invention have been found to be inhibitors of the enzyme glutamate racemase. The activity of the compounds of the present invention as glutamate racemase inhibitors is surprising, because they lack a N-hydroxy substituent. Furthermore, it has been found that 2- and 3-substituted D-glutamic acid derivatives are essentially inactive as inhibitors of this enzyme.

Compounds according to the invention have also been found to possess antibiotic activity, in particular against Streptococcus, especially Streptococcus pneumoniae.

It will be appreciated that the compounds of formula I may exist in and be isolated in at least two different stereoisomeric forms, (2R, 4R) and (2R, 4S) , as well as in mixtures of these two forms (2R, 4R/S) . The present invention provides each of these forms.

Preferred compounds according to the invention have the configuration shown below.

la As used herein, the term (1-lOC) alkyl signifies an unbranched or branched alkyl group containing from one to ten carbon atoms. The term includes within its scope (1- 8C) alkyl, (1-6C) alkyl and (1-4C) alkyl. Examples of particular values for a (1-lOC) alkyl group are methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, t-butyl, pentyl, hexyl, octyl, nonyl and decyl .

The term (2-10C) alkenyl signifies an unbranched or branched alkenyl group containing from two to ten carbon atoms. The term includes within its scope (2-8C) alkenyl, (2-6C) alkenyl and (2-4C) alkenyl . Examples of particular values for a (2-10C) alkenyl group include vinyl and propenyl .

The term (2-10C) alkynyl signifies an unbranched or branched alkynyl group containing from two to ten carbon atoms. The term includes within its scope (2-8C) alkynyl, (2-6C) alkynyl and (2-4C) alkynyl . Examples of particular values for a (2-IOC) alkynyl group include propynyl .

The term (4-IOC) alkadienyl signifies an unbranched or branched alkadienyl group containing from four to ten carbon atoms. The term includes within its scope (4-6C) alkadienyl . An example of a particular value for a (4-10C) alkadienyl group is buta-1 , 3-dienyl .

The term carboxamido (1-8C) alkyl signifies an unbranched or branched (1-8C) lkyl group bearing a terminal carboxamido group. The term includes within its scope carboxamido ( 1- 4C) alkyl. An example of a particular value for a carboxamido (1-8C) alkyl group is carboxamidomethy1.

The term aminocarbonyl (1-8C) alkyl signifies an unbranched or branched (1-8C) alkyl group bearing a terminal aminocarbonyl group. The term includes within its scope aminocarbonyl (1-4C) alkyl . An example of a particular value for an aminocarbonyl (1-8C) alkyl group is aminocarbonylmethyl .

The term^' (3-10C) cycloalkyl includes within its scope (3-7C) cycloalkyl . An example of a particular value for (3- 10C) cycloalkyl group is cyclohexyl .

The term unsubstituted or substituted aromatic group signifies a carbocyclic or heterocyclic aromatic group which is unsubstituted or substituted by one or more substituents, said substituents being selected from atoms and groups that, when present in the compound of formula I, do not prevent it from functioning as a glutamate racemase inhibitor.

The term carbocyclic aromatic group includes phenyl and naphthyl . The term heterocyclic aromatic group includes an aromatic 5-6 membered ring containing from one to four heteroatoms selected from oxygen, sulfur and nitrogen, and a bicyclic group consisting of a 5-6 membered ring containing from one to four heteroatoms selected from oxygen, sulfur and nitrogen fused with a benzene ring or another 5-6 membered ring containing one to four atoms selected from oxygen, sulfur and nitrogen. Examples of heteroaromatic groups are thienyl, furyl, oxazolyl, isoxazolyl, oxadiazoyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl, imidazolyl, triazolyl, tetrazolyl, pyridyl, pyridazinyl, pyrimidyl, benzofuryl, benzothienyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, indolyl and quinolyl . Preferably any aromatic groups are selected independently from phenyl, naphthyl, furyl, thienyl, pyridyl, benzofuryl, benzothienyl, benzothiazolyl and indolyl .

Examples of particular values for an aromatic group are phenyl, naphth-1-yl, naphth-2-yl, fur-2-yl, thien-2-yl, benzothien-2-yl, benzothien-3-yl, pyrid-4-yl, benzofur-2-yl, benzothiazol-2-yl and indol-2-yl.

Preferably each unsubstituted or substituted aromatic group is unsubstituted or substituted by methylenedioxy or by one, two or three substituents selected independently from halogen, (1-4C) alkyl, (1-4C) alkoxy, (1-4C) alkylthio, halo (1-4C) alkyl, halo (1-4C) alkoxy, cyano, nitro, amino, (1- 4C) alkylamino, di (1-4C) alkylamino, carboxy, and a group of formula - (CH^m-X¹- (CH₂)_n-R² in which m is 0, 1 or 2, n is 0, 1 or 2, X¹ represents a bond, 0, S, SO, S0₂, NH, CO, COO, OCO, CONH, NHCO, NHCONH, NHS0₂ or S0₂NH and R² represents an aromatic group which is unsubstituted or substituted by one or two substituents selected independently from halogen, (1- 4C) alkyl, (1-4C) alkoxy, (1-4C) alkylthio, halo (1-4C) alkyl, halo (1-4C) alkoxy, cyano, nitro, amino, (1-4C) alkylamino, di ( 1-4C) alkylamino, carboxy . m is preferably 0 or 1, more preferably 0. n is preferably 0 or 1. X¹ is preferably a bond, 0, NHS0₂ or NHCONH.

Examples of particular values for the aromatic group represented by R² are phenyl, benzothien-2-yl, naphth-1-yl, naphth-2-yl, fur-l-yl, thien-3-yl, benzothien-2-yl and benzofur-2-yl . Examples of particular values for substituents that may be present on an aromatic group represented by R² are fluoro, chloro, methoxy, methylthio, 1-chloroethyl, nitro, amino and N, N-dimethy1amino .

Examples of particular values for substituents that may be present on an unsubstituted or substituted aromatic group are fluoro, chloro, bromo, iodo, methyl, methoxy, phenyl, 4- fluorophenyl, 3-chlorophenyl, 4-chlorophenyl, 4- methoxyphenyl , 4-methylthiophenyl, 4- (1-chloroethyl) phenyl, 3-nitrophenyl, 3-aminophenyl, 4-N,N-diethylaminophenyl, phenoxy, benzyloxy, phenylsulfonylamido, phenylaminocarbonylamido, 2-naphthylphenyl , 5-N,N- dimethylaminonaphth-1-ylsulfonamido, fur-l-yl, thien-3-yl, benzothien-2-yl and benzofur-2-yl .

Examples of particular values for an unsubstituted or substituted aromatic group are phenyl, 3-fluorophenyl, 2,4- difluorophenyl, 3-chlorophenyl, 3-bromophenyl , 3-iodophenyl, 4-iodophenyl, 3-methyIphenyl, 4-methylphenyl, 4-(l- chloroethyl) phenyl, 4-N,N-diethylaminophenyl, 4- phenylphenyl , 4- (4-fluorophenyl) phenyl , 4- (3- chlorophenyl ) phenyl , 4- (4-chlorophenyl) phenyl, 3-(4-(l- chloroethyl) phenyl)phenyl, 4- (4-methoxypheny1)phenyl , 4- (3- nitrophenyl) phenyl, 3- (3-aminophenyl) henyl, 4- (3- aminophenyl) phenyl , 4- (4-methylthiophenyl) phenyl , 4- (2- naphthyl) phenyl , 3- ( fur-2-yl ) phenyl , 4- ( 3-thienyl) phenyl , 3- (benzothien-2-yl) phenyl, 4- (benzothien-2-yl) henyl, 4- (benzofur-2-yl) phenyl, 4-phenoxyphenyl, 4-benzyloxyphenyl, 4-phenylsulfonylamidophenyl, 4- (5-N,N-dimethylaminonaphth-l- ylsulfonylamido) phenyl, naphth-1-yl, naphth-2-yl, 1-methoxy- naphth-2-yl, 7-methoxy-naphth-2-yl, fur-2-yl, thien-2-yl, benzothien-2-yl, 3-chloro-benzothien-2-yl, benzothien-3-yl, 5-fluorobenzothien-3-yl, pyrid-4-yl, benzofur-2-yl, benzothiazol-2-yl and indol-2-yl.

The present invention includes salts of the formula (I) compounds. These salts can exist in conjunction with the acidic or basic portion of the molecule and can exist as acid addition, primary, secondary, tertiary, or quaternary ammonium, alkali metal, or alkaline earth metal salts. Generally, the acid addition salts are prepared by the reaction of an acid with a compound of formula (I) . The alkali metal and alkaline earth metal salts are generally prepared by the reaction of the hydroxide form of the desired metal salt with a compound of formula (I) . The salts of the compounds of formula I may be pharmaceutically-acceptable salts. However, other salts are included in the invention. They may serve as intermediates in the purification of compounds or in the preparation of other, for example pharmaceutically-acceptable, acid addition salts, or are useful for identification, characterisation or purification.

Acid addition salts are preferably the pharmaceutically acceptable, non-toxic addition salts with suitable acids, such as those with inorganic acids, for example hydrochloric, hydrobromic, nitric, sulphuric or phosphoric acids, or with organic acids, such as organic carboxylic acids, for example, glycollic, maleic, hydroxymaleic, fumaric, malic, tartaric, citric, salicyclic, o-acetoxybenzoic, or organic sulphonic, 2-hydroxyethane sulphonic, toluene-p-sulphonic, or naphthalene-2-sulphonic acid.

The present invention includes amides and esters of the compounds of formula I . These amides or esters are useful as intermediates in the preparation of the compounds of formula I or as pro-drugs of the compounds of formula I . Some compounds which are an ester or amide of a compound of formula I have also been found to possess activity as glutamate racemase inhibitors. Examples of esters of compounds of formula I include esters formed between the 1-carboxyl, the 5-carboxyl or the 1- and 5-carboxyl groups in the compound of formula I with a (l-8C)alkanol, such as methanol, ethanol, propanol or butanol; a (1-4C) alkoxy (1-4C) alkanol, such as methoxyethanol; a (3-8C) alkenol, such as allyl alcohol; or an aryl ( (1-4C) alkanol, such as benzyl alcohol.

Examples of amides of compounds of formula I include amides formed between the 1-carboxyl, the 5-carboxyl or the 1- and 5-carboxyl groups in the compound of formula I with ammonia; a (1-4C) alkylamine, such as methylamine; or an arylamine, such as aniline.

It will be appreciated that the compounds of formula I may form a monoester, a diester, a monoamide, a diamide or a mixed ester amide. The ester or amide groups in a diester or diamide may be the same or different.

Amides and esters of the compounds of formula I which are useful as pro-drugs are pharmaceutically acceptable metabolically labile amides and esters of compounds of formula I . These are amide and ester derivatives of compounds of formula I that are hydrolyzed in vivo to afford said compound of formula I and a pharmaceutically acceptable amine or alcohol. Examples of metabolically labile esters include esters formed with (1-6C) alkanols in which the alkanol moiety may be optionally substituted by a (1-8C) alkoxy group, for example methanol, ethanol, propanol and methoxyethanol. The most preferred esters are alkyl esters derived from Cχ_ alkanols, especially methyl and ethyl esters. Preferably X represents a bond, 0 or S .

R¹ preferably represents a methyl, ethyl, propyl, vinyl, prop-2-enyl, prop-2-ynyl, buta-1, 3-dienyl or carboxamidomethyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by an unsubstituted or substituted aromatic group.

According to another aspect, the present invention provides a process for the preparation of a compound of formula I, an ester or amide thereof, or a salt thereof, which comprises (A) hydrolysing a compound of formula

II in which R² represents a hydrogen atom or a carboxyl protecting group and R³ represents a hydrogen atom or an amino protecting group; or

(B) deprotecting a protected compound of formula

III in which R and R ,5^D each represents a hydrogen atom or a carboxyl protecting group and R^δ represents a hydrogen atom or an amino protecting group; or an ester or amide thereof, followed, if desired, by

(i) forming an ester or amide; and

(ii) forming a salt.

The protection of carboxylic acid groups is described in McOmie, Protecting Groups in Organic Chemistry, Plenum Press, NY, 1973, and Greene and Wuts, Protecting Groups in Organic Synthesis, 2nd. Ed., John Wiley & Sons, NY, 1991. Examples of carboxy protecting groups include Ci-Ce alkyl groups such as methyl, ethyl, t-butyl and t-amyl; aryl(Cι- C₄) lkyl groups such as benzyl, 4-nitrobenzyl, 4- methoxybenzyl , 3 , 4-dimethoxybenzyl , 2 , 4-dimethoxybenzyl , 2 , 4, 6-trimethoxybenzyl, 2 , 4, 6-trimethylbenzyl, benzhydryl and trityl; silyl groups such as trimethylsilyl and t- butyldimethylsilyl; and allyl groups such as allyl and 1- ( trimethylsilylmethyl)prop-l-en-3-yl .

Examples of a ine protecting groups include acyl groups, such as groups of formula R⁸C0 in which R⁸ represents Cι_₆ alkyl, C₃_ι₀ cycloalkyl, phenyl Cι_₆ alkyl, phenyl, Cι_6 alkoxy, phenyl Cι_6 alkoxy, or a C₃_ιo cycloalkoxy, wherein a phenyl group may be optionally substituted, for example by one or two of halogen, C₁-C₄ alkyl and Cι-C alkoxy. Preferred amino protecting groups include t-butoxycarbonyl (Boc) and benzyl.

Examples of particular values for R², R⁴ and R⁵ are hydrogen, methyl, ethyl and benzyl.

Examples of particular values for R³ and R⁶ include acetyl and terfc-butoxycarbonyl .

In process step (A) , the hydrolysis is conveniently conducted in the presence of an acid, such as hydrochloric acid, or a base, such as an alkali metal hydroxide, for example lithium, sodium or potassium hydroxide, or an alkaline earth metal hydroxide such as barium hydroxide. Convenient solvents include aqueous ethers, such as tetrahydrofuran. The temperature is conveniently in the range of from 0 to 120°C.

The compounds of formula (III) may be deprotected according to step (B) by conventional methods. Thus, an alkyl carboxyl protecting group may be removed by hydrolysis.^' The hydrolysis may conveniently be performed by heating the compound of formula (III) in the presence of either a base, for example an alkali metal hydroxide such as lithium, sodium or potassium hydroxide, or an alkaline metal hydroxide, such as barium hydroxide or an acid such as hydrochloric acid. The hydrolysis is conveniently performed at a temperature in the range of from 20°C to 300°C. An aryl (C₁-C₄) alkyl carboxyl protecting group may conveniently be removed by hydrogenation. The hydrogenation may be effected by reacting the compound of formula (III) with hydrogen in the presence of a Group VIII metal catalyst, for example a palladium catalyst such as palladium on charcoal . Suitable solvents for the reaction include alcohols such as ethanol . The reaction is conveniently performed at a temperature in the range of from 0° C to 100° C.

An acyl, amine protecting group is also conveniently removed by hydrolysis, for example as described for the removal of an alkyl carboxyl protecting group. Thus, a tert-butoxycarbonyl, amine protecting group may conveniently be removed in the presence of an acid, for example hydrochloric acid or trifluoroacetic acid. The hydrolysis is performed in the presence of a solvent such as water, ethyl acetate or dichloromethane and at a temperature in the range of from 20°C to 100°C. The compounds of formula I may be converted into an ester or amide by a conventional method, for example by reaction of the compound of formula I or a reactive derivative thereof, such as a halide or anhydride, with an appropriate alcohol or amine. Salts of the compounds of formula I, or their esters or amides, may also be formed by a conventional method, such as by reaction with the appropriate acid or base.

Compounds of formula II in which X represents a bond may be prepared by reacting a compound of formula

with a compound of formula

R¹-Z¹ V wherein Z¹ represents a leaving atom or group, in the presence of a strong base.

Compounds of formula II in which X represents a bond may also be prepared from a compound of formula IV via an aldol condensation reaction with an appropriate aldehyde, followed by dehydration of the resultant carbinol and reduction, or a Mannich reaction with an appropriate N,N- dibenzyl-N-methylene halide followed by catalytic hydrogenation to remove the benzyl groups and acylation with a (1-8C) alkanoic acid or reactive derivative thereof. The process comprising a Mannich reaction affords a compound of formula II in which R¹ represents an aminocarbonyl (1-

8C) alkyl group .

Related chemistry references: a) J. Ezquerra, C. Pedregal, A. Rubio, B. Yruretagoyena, A. Escribano, F.

Sanchez-Ferrando, Tetrahedron 1993, 38, 8665-8678. b) J.

Ezquerra, C. Pedregal, B. Yruretagoyena, A. Rubio, M.C.

Carreno, A. Escribano, J.L. Garcia-Ruano, J. Org. Chem.

1995, 60, 2925. See also: J. Ezquerra, C. Pedregal, A. Rubio, J.J. Vaquero, M.P. Matia, J. Martin, A. Diaz, J.L. Garcia Navio, J.B. Deeter, J. Org. Chem. 1994, 59, 4327- 4331.

In the reaction of the compound of formula IV with the compound of formula V, the leaving atom or group represented by Z¹ may be, for example, a halogen atom such as a bromine atom. The strong base may be, for example, lithium bis (trimethylsilylamide) , LHMDS . Convenient solvents include ethers, such as tetrahydrofuran. The reaction is conveniently conducted at a temperature in the range of from

-78 to -20°C.

Compounds of formula II in which X represents 0 may be prepared by reacting a compound of formula

VI with a compound of formula

R -OH VII in the presence of a dehydrating agent, such as diethyl azodicarboxylate (DEAD) with triphenylphosphine .

Compounds of formula VI may be prepared by hydrolyzing a compound of formula

VIII in which R⁹ represents a hydroxyl protecting group, such as t-butoxycarbonyl . The hydrolysis may conveniently be effected in the presence of an acid, such as trifluoroacetic acid.

Compounds of formula VIII may be prepared by oxidizing a compound of formula

IX for example using ruthenium oxide and sodium periodate. Compounds of formula (II) in which X represents S may be prepared by reacting a compound of formula IV with a compound of formula

R^-SR¹ X in the presence of a strong base, such as lithium bis (trimethylsilyla ide) , LHMDS .

Compounds of formula II in which X represents 0 may be prepared by a Mitsunobu type reaction of a compound of formula IX, in which R⁹ is hydrogen, and an aromatic alcohol in the presence of a dehydrating agent, such as

DEAD, and a tertiary phosphine, such as triphenylphosphine .

Compounds of formula II in which R¹ contains a biaryl group may be prepared from a corresponding compound of formula II in which R¹ contains an iodophenyl group by reaction with an arylboronic acid in the presence of a palladium catalyst, such as Pd(Ph₃P)₄- Alternatively, a compound of formula II in which R¹ contains an iodophenyl or bromophenyl group may be reacted with an aryl-tri-n- butylstannane in the presence of triphenylphosphine and Pd₂dba₃ or a similar palladium catalyst, such as Pd(Ph₃P)₄. Related chemistry reference: C. Pedregal, J. Ezquerra, C. Ramirez, J^". Chem. Res . (S) , 1996, 294. It will also be appreciated that compounds of formula II may be converted into other compounds of formula II by conventional methods. For example, a compound of formula II in which R¹ contains an alkenyl group may be reduced to a compound of formula II in which R¹ contains an alkyl group, for example by catalytic hydrogenation in the presence of a palladium catalyst. Compounds of formula II in which X represents S may be converted into compounds of formula II in which X represents SO or S0₂ by reaction with a perbenzoic acid, such as m-chloroperbenzoic acid. Compounds of formula III and esters and amides thereof may be prepared by reacting a compound of formula II with an alkali metal peroxide, such as lithium peroxide, to afford a compound of formula III in which R⁴ represents a hydrogen atom, followed if desired by functionalization of the carboxyl group bearing R⁴.

Many of the intermediates described herein are believed to be novel and are provided as further embodiments of the invention .

As described hereinabove, compounds of formula I have been found to be inhibitors of glutamate racemase and are therefore useful as antibiotics.

The ability of compounds to inhibit glutamate racemase may be demonstrated in the following test.

Glutamate racemase activity was determined by HPLC separation following derivitization with Marfey's reagent. Basically, for a control assay, 6 μg-ml^-1 of glutamate racemase was incubated with L-glutamic acid (10 mM, dissolved in DMSO) for 15 minutes at room temperature (100 μl final volume) . For the test assay in identical conditions, the inhibitor is dissolved in DMSO and mixed with L-glutamic acid in that manner that the final percentage of DMSO present in both control samples and test samples is the same. The enzyme is then added to start the reaction. Both reactions were quenched by addition of 200 μl of 0.2% Marfey's reagent in acetone followed by addition of 40 μl of 1 M sodium bicarbonate. The mixtures were then incubated for 60 minutes at 40² C followed by addition of 20 μl of 2 N HCL. The D- and L- iso ers of glutamic acid were separated by C18 reverse phase chromatography using a linear gradient of 0.05 M triethylamine (pH 3.0) containing 25% (v/v) of acetonitrile to 0.05 M triethylamine (pH 3.0) containing 75% acetonitrile over 20 minutes monitoring absorbance at A340. Quantification of conversion was determined from integrated peak areas from the HPLC [ (D- glutamate peak area) / (L-glutamate peak area + D-glutamate peak area) ] . The test assay is repeated in decreasing concentrations of inhibitors in order to calculate the IC₅0 value for the test compound. All of the compounds of formula I exemplified herein have been evaluated in this test and have been found to give an IC₅₀ of at least 50μM. With a few exceptions, ester and amides derivatives of compounds of formula I have been found to be inactive in this test. The ability of compounds of formula I to function as antibiotics may be demonstrated in the following test of whole-cell activity in S. pneumoniae R6.

Preparation of inoculation stock Medium: Todd Hewitt broth (Difco) supplemented with

0.125% yeast extract (Difco) and 1% IsoVitaleX (BBL) Procedure: Grow S. pneumoniae R6 in above medium at 35°C until the OD₆40 reads 0.4. Aliquot the culture and keep frozen at -80°C. Preparation of inoculum for testing

Medium: Mueller Hinton II (MHII) broth supplemented with 5% lysed horse blood. To prepare lysed horse blood (LHB) , freeze-thaw until blood is thoroughly lysed.

Aseptically mix equal volumes of LHB and sterile water (now 50% LHB) . Centrifuge the blood at 12,000 x g for 20 minutes. Decant the supernatant; recentrifuge if necessary to assure optical clarity. Procedure: Dilute frozen inoculation stock 1:500 in

MHII + 5% LHB, allowing 100 μl per well to be tested. Final dilution of inoculum will be approximately 10⁵ CFU/ml.

Broth microdilution assay 1. Dispense 100 μl MHII with 5% LHB plus 5% DMSO into wells in rows B through H of a 96 well microtiter plate. Dispense 200 μl MHII with 5% LHB (no DMSO) into wells in row A. 2. Dissolve compounds to be tested in DMSO to a concentration of 10 mg/ l. 3. Add 10 μl of the compound solution to the 200 μl of medium in well A. Perform a twofold serial dilution through well G. Resulting concentration range of compound after dilution with inoculum will be 250 - 4 μg/ml .

4. Add 100 μl inoculum for testing to each well. The concentration of DMSO in the test plate after addition of inoculum is 2.5% in each well.

5. Incubate plates at 35°C overnight.

6. The MIC is the lowest concentration of compound that completely inhibits growth as detected by the unaided eye. The animal treated by the compounds according to the invention may be, for example, a warm blooded mammal, such as a mouse, guinea pig, cat, dog, sheep, cow, horse or human, or an avian. Preferably it is a human. The particular effective amount or dose of compound administered according to this invention will of course be determined by the particular circumstances surrounding the case, including the compound administered, the route of administration, the particular condition being treated, and similar considerations. The compounds can be administered by a variety of routes including oral, rectal, transdermal, subcutaneous, intravenous, intramuscular, or intranasal routes. Alternatively, the compound may be administered by continuous infusion. A typical daily dose will contain from about 0.01 mg/kg to about 100 mg/kg of the active compound of this invention. Preferably, daily doses will be about 0.05 mg/kg to about 50 mg/kg, more preferably from about 0.1 mg/kg to about 25 mg/kg. The term "treating" for purposes of the present invention, includes prophylaxis, amelioration or elimination of a named condition once the condition has been established.

The compounds of the present invention are preferably formulated prior to administration. Therefore, another aspect of the present invention is a pharmaceutical formulation comprising a compound of formula I, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof, and a pharmaceutically-acceptable carrier, diluent, or excipient. The present pharmaceutical formulations are prepared by known procedures using well-known and readily available ingredients. In making the compositions of the present invention, the active ingredient will usually be mixed with a carrier, or diluted by a carrier, or enclosed within a carrier, and may be in the form of a capsule, sachet, paper, or other container. When the carrier serves as a diluent, it may be a solid, semi-solid, or liquid material which acts as a vehicle, excipient, or medium for the active ingredient. The compositions can be in the form of tablets, pills, powders, lozenges, sachets, cachets, elixirs, suspensions, emulsions, solutions, syrups, aerosols, ointments containing, for example, up to 10% by weight of active compound, soft and hard gelatin capsules, suppositories, sterile injectable solutions, and sterile packaged powders .

Some examples of suitable carriers, excipients, and diluents include lactose, dextrose, sucrose, sorbitol, annitol, starches, gum, acacia, calcium phosphate, alginates, tragacanth, gelatin, calcium silicate, microcrystalline cellulose, polyvinylpyrrolidone, cellulose, water syrup, methyl cellulose, methyl and propyl hydroxybenzoates, talc, magnesium stearate, and mineral oil. The formulations can additionally include lubricating agents, wetting agents, emulsifying and suspending agents, preserving agents, sweetening agents, or flavoring agents. Compositions of the invention may be formulated so as to provide quick, sustained, or delayed release of the active ingredient after administration to the patient by employing procedures well known in the art .

The compositions are preferably formulated in a unit dosage form, each dosage containing from about 5 mg to about 500 mg, more preferably about 25 mg to about 300 mg of the active ingredient. The term "unit dosage form" refers to a physically discrete unit suitable as unitary dosages for human subjects and other mammals, each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect, in association with a suitable pharmaceutical carrier, diluent, or excipient.

The following formulation examples are illustrative only and are not intended to limit the scope of the invention in any way. Formula ion 1

Hard gelatin capsules are prepared using the following ingredients :

Quantity (mg/capsule)

Active Ingredient 250

Starch, dried 200 Magnesium stearate 10

Total 460 mg

The above ingredients are mixed and filled into hard gelatin capsules in 460 mg quantities.

Formulation 2

Tablets each containing 60 mg of active ingredient are made as follows:

Active Ingredient 60 mg Starch 45 mg

Microcrystalline cellulose 35 mg

Polyvinylpyrrolidone 4 mg

Sodium carboxymethyl starch 4.5 mg

Magnesium stearate 0.5 mg Talc 1 mg

Total 150 mg

The active ingredient, starch, and cellulose are passed through a No. 45 mesh U.S. sieve and mixed thoroughly. The solution of polyvinylpyrrolidone is mixed with the resultant powders which are then passed through a No. 14 mesh U.S. sieve. The granules so produced are dried at 50 ,C and passed through a No. 18 mesh U.S. sieve. The sodium carboxymethyl starch, magnesium stearate, and talc, previously passed through a No. 60 mesh U.S. sieve, are then added to the granules which, after mixing, are compressed on a tablet machine to yield tablets each weighing 150 mg.

The following Examples illustrate the invention.

In the Examples, the following abbreviations are used:

NBS, N-bromosuccinimide; AIBN, 2 , 2 ' -Azobisisobutyronitrile; DMF, dimethylformamide; Et₂0, diethyl ether; hex, hexane;

DIBAL-H, diisobutylaluminium hydride; DEAD, diethylazodicarboxylate; LHMDS, lithium bis ( trimethylsilylamide) or lithium hexamethyldisilazide;

BOC, t-butoxycarbonyl; DMAP, 4-dimethylaminopyridine; Et₃N, triethylamine; rt, room temperature; EtOAc, ethyl acetate;

Pd₂dba₃, palladium bis (dibenzylideneacetone) ; EDCI, ethyl-

N,N-diethylaminopropyl carbodiimide, hydrochloride salt;

BtOH, 1-hydroxybenzotriazole .

Materials and Methods. All solvents and reagents were purchased from commercial sources, unless otherwise indicated. Tetrahydrofuran (THF) was distilled from sodium benzophenone ketyl prior to use. All reactions were performed under a positive pressure of nitrogen or argon.

^XH-NMR and ¹³C-NMR data were recorded on a Brucker AC-200P (200 MHz) . Melting points were determined on a Buchi apparatus and are not corrected. Optical rotations were measured in a Perkin-El er 241 polarimeter. Analytical TLC was performed on Merck TLC glass plates precoated with F254 silica gel 60 (UV, 254 run and iodine) . Chromatographic separations were performed by using 230-400 mesh silica gel (Merck) . Elemental analyses were performed by the Universidad Complutense Madrid.

Synthesis of non-commercially available alkyl bromides:

General procedure for the radical bro ination of methyl heterocycles .

To a solution of the starting material (8 mmol) in 25 ml of anhydrous CC1₄ under N₂, NBS (8 mmol, 1.0 equiv) and a catalytic amount of AIBN (5 mol%) were added and the mixture refluxed for 4 hours or until TLC showed complete conversion. The reaction mixture was cooled to 0 °C, filtered through a pad of Celite and evaporated to afford a crude oil which was used as it was or recrystallyzed from mixtures CH₂C1₂/Hex at -10 °C when possible. For all the compounds ¹H-NMR data is consistent with structures.

2-Thienylmethyl bromide. 60% yield. Yellow oil.

3-Benzo [b] thienylmethyl bromide . 51% yield. Brownish solid.

5-Fluoro-3-benzo [b] thienylmethyl bromide . 41% yield. Brownish solid.

General procedure for the synthesis of alkylbromides via bromination of aryl-methyl alcohols.

First step. Synthesis of C-2 heterocyclic aldehydes. To a solution of the heterocycle (20 mmol) in 120 ml of anhydrous THF under N₂ and cooled to -78 °C, n-BuLi (1.1 equiv) is dropwise added and the mixture stirred for lh at - 78 °C. Then anhydrous DMF (3.0 equiv) is added and the solution stirred for 2h while warming up the reaction to -10 °C. The reaction was hydrolyzed with saturated NH₄C1, diluted with water, extracted with Et0, and the organic layer washed with water and brine. Drying over MgSθ₄ and evaporation afforded a crude aryl-aldehyde which was used as it was. Yields >90% for all compounds and ¹H-NMR data consistent with structure.

Second step. Synthesis of C-2 heterocylcic methyl alcohols. To a solution of the aldehyde (20 mmol) in 100 ml of anhydrous THF under N₂ and cooled to -78 °C, DIBAL-H (1M solution in Hex, 1.05 equiv) is dropwise added and the mixture stirred for lh at -78 °C and then hydrolyzed with saturated NH₄C1, diluted with Et₂0 and IN HC1. The organic layer was washed with IN HCl, and the aqueous phase extracted with Et₂0 and the combined organic layers washed with water and brine. Drying over MgS0₄ and evaporation afforded a crude aryl-methylalcohol which was used as it was or recrystallyzed from mixtures CH₂C1 /Hex at -10 °C when possible. Yields >70% for all compounds and ¹H-NMRs consistent with structure. Third step. Acid catalyzed bromination of alcohols.

To a solution of the starting alcohol (6.6 mmol) in 20 ml of anhydrous CH₂C1₂ was added HBr (48% solution in water, 2.0 equiv) and a catalytic amount of cone. H₂Sθ₄ (20 mol%) . The mixture was stirred for 1.5 h or until TLC showed complete conversion, then neutralyzed by pouring into an iced-cooled solution of saturated NaHC0₃, extracted with CH₂C1₂ and the organic layer washed with saturated NaHC0₃ and brine. Drying over NaS0₄ and evaporation afforded a crude aryl- methylbromide which was used as it was. Yields ranging from 50 to 90%. ¹H-NMRs consistent with structure.

2-Benzo [bj thienylmethyl bromide . Prepared in three steps from benzothiophene. Brownish solid.

3-Chloro-2-benzo [b] thienylmethyl bromide . Brownish solid.

2-Benzo [b] furylmethyl bromide . Prepared in three steps from benzofuran. Brownish solid.

N-Benzenesulfonyl-2-indolylmethyl bromide . Prepared in three steps from 1-benzenesulfonyl indol. Brownish solid.

2-Bromomethylbenzothiazol (Prepared as described by Tsukiyama, Takahiro; Sato, Kazuo . Preparation of benzothiazole and benzoxazoles . Jpn. Kokai Tokkyo Koho 14 pp. CODEN: JKXXAF JP 10045735 A2 980217 Heisei. CAN 128:140695; AN 1998:118690): 2-aminothiophenol (1.1 ml, 10 mmol) and 2-bromoacetyl bromide (0.91 ml, 10.5 mmol) were dissolved in acetic acid (5 ml) under nitrogen atmosphere and refluxed for 1 hour. The reaction mixture was cooled to room temperature and poured into an ice cooled NaHC0₃ solution in water, extracted with ether and EtOAc and the combined organic layers washed several times with saturated NaHC0₃. The organic layer was dried over Na₂S0₄ and concentrated, and the residue chromatographed (Si0₂, Hex/EtOAc 8/1) . ¹H-NMR consistent with structure.

Synthesis of C-4 Substituted D-Glutamic Acids

EXAMPLE 1.

{2R, AS) -2-Amino-4- (2-naphthyl)methyl pentanedioic acid. STEP 1A. (D) -Ethyl pyroglutamate . (Prepared as described by Silverman, R. B.; Levy, M. A. J. Org. Chem. 1980, 45, 815). To a suspension of (D) -glutamic acid (25.6 g, 175 mmol) in anhydrous ethanol (250 ml) cooled to 0^aC, thionyl chloride (30 ml, 410 mmol) freshly distilled was dropwise added. The resulting solution was stirred for lh at room temperature and a further half an hour under reflux. The solution was neutralized with 10% KOH (in EtOH) . The precipitate was filtered off and the solvent evaporated. The resulting residue was distilled (90^aC/ 0.5 mm Hg) yielding a colorless oil which solidified on standing (26.3 g; 95%) . ¹H NMR consistent with structure.

STEP IB. (D) -Ethyl N-BOC-pyroglutamate .

(Prepared as described by Flynn, D. L.; Zelle, R. E.; Grieco, P. A. J. Org. Chem. 1983, 48, 2424) . To a solution of (D) -Ethyl pyroglutamate (26.28 g, 167 mmol) in anhydrous acetonitrile (420 ml) di-tert-butyl dicarbonate (40.17 g, 184 mmol) and DMAP (2.0 g, 16.7 mmol) were added. After stirring for 4 h at rt the solvent was evaporated. The resulting residue was dissolved in ether and washed with IN HC1 (3 X 150 ml) . The aqueous solution was extracted with Et₂0. The combined organic layers were washed with IN HC1 aqueous solution, saturated sodium bicarbonate and brine. After drying over Na₂Sθ₄, the solvent was evaporated to yield a colorless oil which solidified on standing. Yield: 29.3 g (69%) . ^Ή NMR consistent with structure.

STEP lC. Ethyl {2R, AS) -1- (tert-butoxycarbonyl) -4- (2- naphthyl ethyl) pyroglutamate . To a solution of (D) -Ethyl N-BOC-pyroglutamate (7.77 mmol) in dry THF (40 ml) under argon was added a 1M solution of lithium hexamethyldisilazide (LHMDS) in dry THF (8.55 ml) at -78 ^aC. After 1 hour, a solution of 2-naphthylmethyl bromide, 9.3 mmol) in dry THF (20 mL) was added, and stirring continued at -78 ^aC for 2 hours. The reaction mixture was quenched with saturated ammonium chloride solution (50 mL) at -78 ^aC and extracted with ethyl ether (3 x 20 ml) . The combined organic phases were dried over Na₂S0₄, filtered and evaporated to dryness obtaining a crude product which was purified by column chromatography (Hex/EtOAc 3:1) to yield the pure trans isomer (2R, AS) . X NMR consistent with structure. 48%. White solid, mp 124^s C.

STEP ID. Preparation of the final compound.

To a solution of Ethyl ( 2R, AS) -1- (tert-butoxycarbonyl) -4- (2- naphthylmethyl) pyroglutamate (2 mmol) in tetrahydrofuran (15 ml) was added a 2.5 N aqueous solution of LiOH (14.4 ml, 36 mmol) . The mixture was stirred at room temperature for 2h, then acidified to pH 2 with IN HC1 solution and extracted with ethyl ether (3 x 20 ml) . The combined organic layers were dried over Na₂S0₄ and concentrated in vacuo to give a residue which was diluted and stirred with 15 ml of a saturated dry HCl solution in ethyl acetate for one hour at room temperature. The resulting white solid was filtered off and triturated with ethyl ether (3 x 20 ml) to afford the hydrochloride salt. The compound was dissolved in the minimum amount of MeOH (ca. 5 ml) and treated with an excess of propylene oxide at room temperature until the zwitterion salt precipitates (l-16h) . The solids were filtered off and dried under high vacuum to yield (2R, 4S) -2-Amino-4- (2- naphthyl) meth l pentanedioic acid. Yield: 72%. mp 144 ^aC, 72 % yield. [α]_D= -21.5 (c 1.0, MeOH). ^XH NMR (MeOH-d₄) : 7.83- 7.77 (m, 3H) , 7.69 (s, 1H) , 7.49-7.36 (m, 3H) , 3.99 (dd, J^" = 5.5 and 8.5 Hz, 1H) , 3.26-3.19 (m, 1H) , 3.09-2.97 (m, 2H) , 2.43-2.28 (m, 1H) , 2.00-1.86 (m, 1H) . ¹³C NMR (MeOH-d₄) : 177.3, 171.4, 137.8, 134.8, 133.7, 129.2, 128.7, 128.5 128.3, 127.0 126.6, 52.5, 44.4, 39.3, 32.8. EXAMPLE 2 .

( 2R, AS) -2-Amino-4- (m-bromo) benzyl pentanedioic acid.

STEP 2A. Ethyl ( 2R, AS) -1- (tert-butoxycarbonyl) -A- (m- bromo) benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using m- bromobenzyl bromide as reagent. X NMR consistent with structure. 93%. White solid, mp 88-89 °C . [α]_D= +25.2 (c 1.37, CHC1₃) .

STEP 2B.

{2R, S) -2-Amino-4- (m-bromo) benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 174-175 ^aC. [α]_D= -41.4 (c 0.5, IN HC1) . hl-NMR (D₂0/KOD) δ 7.41 (s, 1H) , 7.30-7.13 ( , 3H) , 3.23-3.18 (m, 1H) , 2.95-2.87 (m, 1H) , 2.66-2.61 (m, 2H) , 2.01-1.96 ( , 1H) , 1.51-1.46 (m, 1H) . ¹³C-NMR (D₂0/KOD/MeOH- d₄) : 183.4, 182.9, 144.9, 133.0, 131.0 129.9, 129.1, 123.1, 56.2, 49.5, 40.6.

EXAMPLE 3. (2R, S) -2-Amino-4- (p-phenyl) benzyl pentanedioic acid.

STEP 3A. Ethyl ( 2R, AS) -1- (tert-butoxycarbonyl) -4- (p- bro o) benzyl pyroglutamate .

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using p-bromo benzyl bromide as reagent. White solid, mp 156-157^aC, 79 % yield. [α]_D= -35^a (c 0.5, 2N NaOH) . ^XH-NMR (MeOH-d₄/KOD) δ 7.35 and 7.15 (AA'BB' system, 4H) , 3.22 (m, 1H) , 2.90 (m, 1H) , 2.70- 2.50 ( , 2H) , 2.05 (rα, 1H) , 1.48 (rα, 1H) . ¹³C-NMR (MeOH- d₄/KOD) δ 183.5, 182.7, 141.6, 132.2, 120.5, 56.3, 49.3, 40.6, 40.3.

STEP 3B. Ethyl {2R, AS) -1- (tert-butoxycarbonyl) -4- (p- phenyl) benzyl pyroglutamate .

To a solution of Ethyl- (2R, S) -A- (p-bromo) -benzyl pyroglutamate (1.0 mmol) and phenyl-tri-n-butylstannane (1.0 mmol) in 7 ml of anhydrous DMF under N₂, Pd(Ph₃P)4 (5 mol%) was added. The resulting solution is heated at 120 °C for 2 h and then cooled to room temperature and diluted with Et₂0 and water (25 ml each) . The aqueous layer is extracted with Et₂0, and the organic phase washed with water, satd solution of KF, water and brine. The organic phase is dried over MgS0₄ and evaporated to afford a crude product which was purified by silica gel chromatography (in gradient, from

Hex/EtOAc 20:1 to 2:1) to yield pure coupling compound as a clear oil. Yield: 70%. X NMR consistent with structure.

White solid, mp 97-98 °C . [ ]_D= +5.4 (c 0.22, CHCl₃) .

STEP 3B.

(2R, S) -2-Amino-4- (p-phenyl ) benzyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, step ID. White solid, mp 98-99 °C . X NMR (MeOH- d₄/KOD) : 7.58-7.12 (m, 9H) , 3.29-3.12 (m, 1H) , 3.11-2.88 (m, 1H) , 2.79-2.55 ( , 2H) , 2.05 ( , 1H) , 1.47 ( , 1H) . ¹³C NMR (MeOH-d₄/KOD) : 184.0, 183.3, 142.2, 143.3, 139.9, 132.1, 130.7, 129.8, 128.1, 127.7, 56.4, 40.7, 40.5.

EXAMPLE 4. (2JR, 4.R) -2-Amino-4- (2-thienyl) ethyl pentanedioic acid.

STEP 4A. Ethyl (2R, AR) -1- (tert-butoxycarbonyl) -4- (2- thienyl) methyl pyroglutamate . The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 2-thienylmethyl bromide as reagent. ¹H NMR consistent with structure. 54%. Oil.

STEP 4B.

( 2R, AR) -2-Amino-4- (2-thienyl) methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. Pale cream solid. 38%. mp 119-120 °C. [ ]_D= -12.7 (c 0.36, HC1) . NMR data consistent with structure.

EXAMPLE 5.

(21?, AS) -2-Amino- [ (1-methoxy) -2-naphthyl] methyl pentanedioic acid.

STEP 5A. Ethyl (2R, AS) -1- (tert-butoxycarbonyl) -4- [ (1- methoxy) -2-naphthyl] ethyl pyroglutamate.

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using l-methoxy-2- naphtylmethyl bromide as reagent. Pale cream solid. 40%. [α]_D= +25.6 (c 0.32, CHC1₃) . X NMR (CDC1₃) : 7.97 (dd, J = 7.7 and 1.9 Hz, 1H) , 7.73 (dd, J^" = 7.3 and 2.7 Hz, 1H) , 7.47 (t, J = 8.3 Hz, 1H) , 7.39 (m, 2H) , 7.21 (d, J^" = 8.3 Hz, 1H) , 4.40 (dd, J = 9.2 and 2.0 Hz, 1H) , 4.06 (qd, J = 7.1 and 1.3 Hz, 2H) , 3.82 (s, 3H) , 3.36 (dd, J = 13.1 and 3.8 Hz, 1H) , 2.97 (m, 1H) , 2.80 (dd, J = 13.1 and 10.0 Hz, 1H) , 2.10-1.82 (m, 2H) , 1.42 (s, 9H) , 1.13 (t, J = 7.1 Hz, 3H) .

STEP 5B.

( 2R, AS) -2-Amino-4- [ (1-methoxy) -2-naphthyl] methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 31%. Mp 147-148 °C. X NMR (D₂0/KOD) : 8.04 ( , 1H) , 8.62 (m, 1H) , 7.45-7.32 (m, 4H) , 3.99 ( , 1H) , 3.98 ( , 3H) , 3.25-2.98 (m, 3H) , 2.22-2.10 (m, 1H) , 2.05-1.85 (m, 1H) .

EXAMPLE 6. (2jR, AS) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid.

STEP 6A. Ethyl (2R, AS) -1- (tert-butoxycarbonyl) -4- (3-benzo [b] thienyl) methyl pyroglutamate. The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 3- (benzo [b] thienyl) methyl bromide as reagent. NMR data consistent with structure. White solid. 50%. ¹H NMR (CDC1₃) : 7.85 (m, 1H) , 7.74 (m, 1H) , 7.43-7.26 (m, 2H) , 7.12 (brs, 1H) , 4.49 (dd, J = 8.9 and 2.2 Hz, 1H) , 4.17 (qd, J^" = 7.3 and 1.3 Hz, 2H) , 3.53 (ddd, J = 14.1, 4.5 and 1.0 Hz, 1H) , 3.10-2.84 (m, 2H) , 2.11-1.97 (m, 2H) , 1.50 (brs, 9H) , 1.24 (t, J^" = 7.2 Hz, 3H) .

STEP 6B.

(2R, AS) -2-Amino-4- (3-benzo [b] thienyl)methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. ¹H NMR consistent with structure. White solid. 40%. mp 121-123 °C . [α]_D= -15.2 (c 0.61, IN HCl) .

EXAMPLE 7.

(2R, R) -2-Amino-4- (2-benzo [b] thienyl) ethyl pentanedioic acid.

STEP 7A. Ethyl (2R, AR) -1- (tert-butoxycarbonyl) -4- (2- benzo [b] thienyl)methyl pyroglutamate .

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 2- (benzo [b] thienyl) methyl bromide as reagent. ¹H NMR consistent with structure. White solid. 51%. mp 141-142 °C.

[CC]_D= +27.9 (c 0.31, CHC1₃) . ^XH NMR (CDC1₃) : 7.76-7.56 (m, 2H) , 7.29-7.14 ( , 2H) , 6.98 (s, 1H) , 4.44 (dd, J = 9.0 and 1.9 Hz, 1H) , 4.12 (q, J = 7.1 Hz, 2H) , 3.41 (m, 1H) , 2.96 (m, 2H) , 2.20-1.92 (m, 2H) , 1.42 (s, 9H) , 1.19 (td, J- = 7.1 and 0.6 Hz, 3H) .

STEP 7B.

10 ( 2R, AR) -2-Amino-4- (2-benzo [b] thienyl) methyl pentanedioic acid was- prepared following a similar procedure as described for Example 1, Step ID. White solid. 71%. mp 167-168 °C.

[ ]_D= -35.3 (c 0.55, IN HCl) . X NMR (D₂0/KOD) : 7.53 (brd, J = 7.3 Hz, 1H) , 7.43 (brd, J = 8.1 Hz, 1H) , 7.02 (m, 2H) , 15 6.80 (brs, 1H) , 2.92 (brdd, J = 8.5 and 4.3 Hz, 1H) , 2.84- 2.65 (m, 2H) , 2.44 ( , 2H) , 1.69 (m, 1H) , 1.30 (m, 1H) . ¹³C NMR (D₂0/KOD/MeOH-d₄) : 183.9, 183.6, 145.2, 140.8, 140.0, 125.2, 124.6, 123.8, 123.1, 122.6, 55.5, 48.9, 39.5, 34.6.

20 EXAMPLE 8.

( 2R, R) -2-Amino-4- [ ( 3-chloro) -2-benzo [b] thienyl] methyl pentanedioic acid.

STEP 8A. Ethyl ( 2R, AR) -1- (tert-butoxycarbonyl) -4- [ (3- 25 chloro) -2-benzo [b] thienyl] methyl pyroglutamate.

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 3-chloro-2- (benzo [b] thienyl) methyl bromide as reagent. NMR data consistent with structure. White solid. 30%. ¹H NMR (CDCI₃) : 3.0 7.75 (dd, J = 7.8 and 0.8 Hz, 2H) , 7.47-7.32 (m, 2H) , 4.53

(dd, J = 7.2 and 0.8 Hz, 1H) , 4.19 (q, J^" = 7.1 Hz, 2H) , 3.55 (m, 1H) , 3.17-3.02 (m, 2H) , 2.14 (m, 2H) , 1.51 (brs, 9H) , 1.26 (td, J = 7.1 and 0.7 Hz, 3H) . STEP 8B .

(22?, 41?) -2-Amino-4- [ (3-chloro) -2-benzo [b-] thienyl] methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 43%. mp 137-138 °C . X NMR (D₂0/K0D) : 7.54 (dd, J = 6.5 and 1.2 Hz, 1H) , 7.44 (dd, J = 6.5 and 1-.4 Hz, 1H) , 7.20-7.05 (m, 2H) , 2.93 (dd, J = 9.5 and 4.3 Hz, 1H) , 2.80 (m, 2H) , 2.47

(m, 1H) , 1.73 (m, 1H) , 1.31 (m, 1H) . ¹³C NMR (D₂0/KOD/MeOH- d₄) : 183.4, 183.4, 137.9, 137.5, 137.3, 126.1, 125.9, 123.6, 122.1, 118.6, 55.7, 48.0, 39.6, 32.5.

EXAMPLE 9.

( 2R, S) -2-Amino-4- [ (5-fluoro) -3-benzo [b] thienyl]methyl pentanedioic acid.

STEP 9A. Ethyl ( 2R, AS) -1- (tert-butoxycarbonyl) -4- [ (5- fluoro) -3-benzo [b] thienyl] methyl pyroglutamate. The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using 5- fluoro-3- (benzo [b] thienyl) methyl bromide as reagent. NMR data consistent with structure. White solid. 38%. ""^"H NMR (CDC1₃) : 7.77 (dd, J = 8.7 and 4.8 Hz, 1H) , 7.39 (dd, J = 9.6 and 2.4 Hz, 1H) , 7.27 (s, 1H) , 7.12 (td, J = 8.7 and 2.4 Hz, 1H) , 4.51 (dd, J = 9.2 and 1.8 Hz, 1H) , 4.19 (q, J = 7.1 Hz, 2H) , 3.43 (dd, J = 14.1 and 2.9 Hz, 1H) , 3.02 (m, 1H) , 2.89 (dd, J = 14.1 and 8.9 Hz, 1H) , 2.20-1.98 ( , 2H) , 1.51 (s, 9H) , 1.26 (t, J = 7.1 Hz, 3H) .

STEP 9B.

{ 2R, AS) -2-Amino-4- [ (5-fluoro) -3-benzo [b] thienyl]methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 56%. mp 224 °C (dec). X NMR (D₂0/K0D) : 7.56 (ddd, J = 9.1, 5.2 and 2.3 Hz, 1H) , 7.26 (dt, J = 10.4 and 2.3 Hz, 1H) , 7.05 (brd, J = 1.7 Hz, 1H) , 6.89 (tt, J^" = 9.1 and 2.3 Hz, 1H) , 2.96 (m, 1H) , 2.77-2.61 (m, 2H) , 2.50 (m, 1H) , 1.73 ( , 1H) , 1.34 (m, 1H) . ¹³C NMR (D₂0/K0D/Me0H-d₄) : 184.4, 183.6, 161.7 (d, J = 239 Hz) , 141.1 (d, J = 9.2 Hz) , 136.4, 135.6 (d, J = A. A Hz), 126.2, 125.1 (d, J = 10.3 Hz) , 113.8 (d, J = 23.9 Hz) , 108.4 (d, J = 21.5 Hz) , 55.8, 47.2, 40.0, 32.6.

EXAMPLE 10. (2R, AS) -2-Amino-4- (pyridyl) thio pentanedioic acid, hydrochloride salt.

STEP IQA. Ethyl (2 R, AS) -1- (tert-butoxycarbonyl) -4- (pyridyl) thio pyroglutamate. The title compound was prepared in a manner analogous to that described for Example 1, Step IC, using 4-pyridyl disulfide as reagent and an excess (2.0 equiv) of LHMDS . Particular procedure described by J. Ezquerra et al, Tetrahedron 1993, 49, 8665-8678. The product was obtained as an inseparable mixture of 4S/4R diastereomers in 2:1 ratio, respectively. NMR data consistent with structure. Cream solid. 85% overall yield. ¹H NMR (CDCl₃) minor diastereomer : 8.45 (d, ^" = 5.7 Hz, 2H) , 7.31 (d, J = 6.3 Hz, 2H) , 4.66 (t, J = 4.9 Hz, 1H) , 4.32-4.10 (m, 3H) , 2.96 (dt, J = 14.1 and 9.3 Hz, 1H) , 2.23-2.08 (m, 1H) , 1.52 (s, 9H) , 1.32 (t, J^" = 7.1 Hz, 3H) . Major diastereomer: 8.45 (d, J = 5.7 Hz, 2H) , 7.31 (d, J^" = 6.3 Hz, 2H) , 4.63 (dd, J = 9.4 and 2.4 Hz, 1H) , 4.32-4.10 (m, 3H) , 2.58 (ddd, J = 13.8, 8.8 and 2.4 Hz, 1H) , 2.34 (ddd, J = 13.8, 9.4 and 1.3 Hz, 1H) , 1.52 (s, 9H) , 1.31 (t, J^" = 7.1 Hz, 3H) .

STEP 10B.

{2R, AS) -2-Amino-4- (pyridyl) thio pentanedioic acid hydrochloride salt was prepared by refluxing a mixture of the corresponding pyroglutamate (2 mmol) and a 6N aqueous HCl solution (25 ml) for 16 hours. The resulting solution was evaporated to dryness yielding a white solid which was triturated with ethyl ether, filtered off and dried under high vacuum. The compound was obtained as a 2:1 mixture of 4S/4R diastereomers. Cream solid. 78% overall. ^XH NMR (MeOH- d₄) mixture of diastereomers: 8.60 (m, 4H) , 8.08 (m, 4H) , 4.87 (m, 2H) , 4.27 (m, 2H) , 2.91-2.34 ( , 4H) . ¹³C NMR (MeOH- d₄) mixture of diastereomers: 171.9, 171.8, 170.6, 170.5, 163.7, 163.6, 141.0, 140.9, 140.6, 124.6, 124.5, 124.4, 124.3, 51.7, 51.6, 44.9, 44.8, 32.5, 32.3.

EXAMPLE 11.

( 2R, AR) -2-Amino-4- (2-benzo [b] furyl) methyl pentanedioic acid.

STEP 11A. Ethyl {2R, AR) -1- (tert-butoxycarbonyl) -A- (2- benzo [b] furyl) methyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using 2- (benzo [b] furyl) methyl bromide as reagent. NMR data consistent with structure. White solid. 65%. ^XH NMR (CDC1₃) : 7.51-7.38 ( , 2H) , 7.23 (m, 2H) , 6.48 (d, J = 0.8 Hz, 1H) , 4.54 (dt, J = 9.3 and 1.6 Hz, 1H) , 4.20 (qd, J = 7.1 and 1.7 Hz, 2H) , 3.40 (dd, J= 14.8 and 3.8 Hz, 1H) , 3.06 ( , 1H) , 2.87 (ddd, J^" = 14.9, 9.2 and 1.0 Hz, 1H) , 2.32-1.99 (m, 2H) , 1.51 (s, 9H) , 1.27 (td, J = 7.1 and 1.8 Hz, 3H) .

STEP 11B.

{ 2R, AR) -2-Amino-4- (2-benzo [b] furyl)methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 70%. mp 178-179 °C.

[α]_D= -35.3 (c 0.50, IN HCl). ^XH NMR (D₂0/K0D) : 7.36 (brd, J = 6.5 Hz, 1H) , 7.29 (brd, J= 7.2 Hz, ^'lH), 7.05 (m, 1H) , 6.36 (brs, 1H) , 3.14 ( , 1H) , 2.90-2.54 ( , 3H) , 1.83 (m, 1H) , 1.41 ( , 1H) . ^X3C NMR (D₂0/ 0D/Me0H-d₄) : 184.1, 183.7, 158.9, 155.4, 129.8, 124.6, 123.8, 121.7, 111.9, 104.0, 55.8, 46.0, 39.7, 32.7.

EXAMPLE 12

(22?, AR) -2-Amino-4- (2-indolyl) methyl pentanedioic acid, hydrochloride salt .

STEP 12A. Ethyl (2R, AR) -1- (tert-butoxycarbonyl) -4- [2- (N- benzenesulfonyl ) indolyl] methyl pyroglutamate . The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 2- (N- benzenesulfonyl) indolyl methyl bromide as reagent. NMR data consistent with structure. White solid. 60%. mp 84-85 °C . [α]_D= -54.0 (c 0.74, CHC1₃) . ^XH NMR (CDC1₃) : 8.24 (dt, J = 8.3 and 1.3 Hz, 1H) , 7.77-7.70 (m, 2H) , 7.58-7.29 (m, 7H) , 4.58 (dd, J = 9.5 and 1.3 Hz, 1H) , 4.20 (qd, J = 7.1 and 1.5 Hz, 2H) , 3.73 (dd, J = 14.2 and 4.0 Hz, 1H) , 3.38 (m, 1H) , 3.17 (dd, J^" = 14.2 and 10.9 Hz, 1H) , 2.29 (ddd, .7 = 13.2, 11.9 and 9.5 Hz, 1H) , 2.04 (ddd, J = 13.2, 8.5 and 1.3 Hz, 1H) , 1.53 (s, 9H) , 1.26 (t, J = 7.1 Hz, 3H) .

STEP 12B. (22?, 41?) -2-Amino-4- (2-indolyl) methyl pentanedioic acid, hydrochloride salt was prepared as follows: The corresponding ethyl D-pyroglutamate (0.28 mmol) was dissolved in 5 ml of MeOH and 1 ml of 2N NaOH was added. The reaction mixture was refluxed for 16h and then cooled to room temperature and evaporated to dryness. The residue was diluted with water, acidified to pH 2 with IN HCl, extracted with Et₂0 (4 x 10 ml) , dried over Na₂S0 to afford, after evaporation, a foamy solid which was dissolved in a saturated solution of HCl in EtOAc . The mixture was stirred for 2h, the solvent evaporated and the HCl salt triturated with Et₂0 and dried under high vacuum. Greenish solid, 60%. mp 154-156 °C. [α]_D= -10.0 (c 0.6, MeOH). ^XH NMR (Me0H-d₄) : 7.48-6.90 ( , 5H) , 4.01 (m, IH) , 3.09 (m, 3H) , 2.41 (m, IH) , 1.93 (m, IH) . ¹³C NMR (MeOH-d₄) : 176.8, 171.3, 134.0, 128.5, 123.3, 122.2, 121.0, 120.9, 119.0, 112.4, 52.5, 49.7, 42.7, 30.3.

EXAMPLE 13. (22?, AS) -2-Amino-4- (prop-2-ynyl) pentanedioic acid.

STEP 13A. Ethyl (22?, AS) -1- (tert-butoxycarbonyl) -4- (prop-2- ynyl) pyroglutamate.

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using propargyl bromide as reagent and changing the order of addition: the enolate solution over the electrophile (4 equiv) . NMR data consistent with structure. White solid. 65%. mp 91-95%.

STEP 13B.

(22?, AS) -2-Amino-4- (prop-2-ynyl) pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 26%. mp 164 °C . [oc]_D ^2Q= - 54.5 (c 0.11, IN HCl) . ¹H-NMR (D₂0/KOD) : 2.93 (dd, J = 9.4, 5.1 Hz, IH) , 2.27 (t, J^" = 5.7 Hz, IH) , 2.13 (s, IH) , 2.11

(d, J^" = 6.4 Hz, IH) , 1.72-1.58 (m, IH) , 1.45-1.30 (m, IH) . ^X3C-NMR (D₂0/Pyridine-d5) : 180.6, 173.7, 81.9, 70.3, 52.6, 43.2, 31.6, 21.2.

EXAMPLE 14

(22?, AS) -2-Amino-4- (3-phenyl-prop-2-ynyl) pentanedioic acid. STEP 14A. Ethyl (22?, AS) -1- (tert-butoxycarbonyl) -4- (3-phenyl- prop-2-ynyl) pyroglutamate.

Ethyl (22?, AS) -1- (tert-butoxycarbonyl) -4- (prop-2- ynyl ) pyroglutamate (600 mg, 2.11 mmol) was dissolved in triethylamine (18 ml) and to this solution was added iodobenzene (0.315 ml, 2.81 mmol), PdCl₂(PPh₃)₂ (84.2 mg, 0.12 mmol) and Cul (11.43 mg, 0.06 mmol). The reaction mixture was stirred under air atmosphere at room temperature overnight. The yellow slurry formed was concentrated to dryness under reduced pressure and the residue purified by chromatography (Hex/EtOAc 4:1) to afford a white solid, 550 mg, 71%. NMR data consistent with structure.

STEP 14B. (22?, 45) -2-Amino-4- (3-phenylprop-2-ynyl) pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid. 43%. mp 157 °C. [α]_D ²⁰ = -39.0 (c 0.205, IN HCl) . ^XH-NMR (D₂0/KOD) : 7.24-7.02 ( , 5H) , 3.04-2.92 (m, IH) , 2.48-2.30 (m, 3H) , 1.81-1.62 (m, IH) , 1.53-1.37 (m, IH) . ¹³C-NMR (D₂0/Pyridine-d5) : 180.7,

173.8, 131.0, 127.9, 127.7, 122.2, 87.4, 81.6, 52.7, 43.4, 31.8, 22.3.

EXAMPLE 15. (22?, 42?) -2-Amino-4- (2-benzo [b] thiazolyl) methyl pentanedioic acid, hydrochloride salt.

STEP 15A. Ethyl (22?, 42?) and (22?, 45) -1- (tert-butoxy carbonyl) -4- (2-benzo[b] thiazolyl) methyl pyroglutamate. The title compound was prepared as an inseparable mixture of epimers at C-4 in an analogous manner to that described for Example 1, Step IC, using 2- (benzo [b] thiazolyl) ethyl bromide as reagent. NMR data consistent with structure. White solid. 65%. STEP 15B .

(2E, 42?) -2-Amino-4- (2-benzo[b] thiazolyl)methyl pentanedioic acid, hydrochloride salt, was prepared in an analogous manner to that described for Example 10, Step 10B, as a mixture of 4R/4S diastereomers. 98% overall, mp 131 °C. ^XH- NMR (Methanol-d4) : (Data for the major isomer) 8.23 (d, J^" = 7.1 Hz, IH) , 8.07 (d, J = 7.5 Hz, IH) , 7.83-7.63 (m, 2H) , 4.37-4.25 (m, IH) , 3.81 (d, J = 7.35 Hz, IH) , 3.79 (s, IH) , 3.64-3.34 (m, IH) , 2.66-2.13 (m, 2H) . ^X3C-NMR (Methanol-d4) : (Data for the major isomer): 177.9, 174.8, 171.0, 144.1, 133.2, 130.1, 128.8, 124.7, 119.6, 52.2, 42.9, 34.7, 33.2.

EXAMPLE 16. (22?, 42?) -2-Amino-4- (N-benzoylamino) methyl pentanedioic acid.

STEP 16A. Ethyl ( 2R, AR) -1- (tert-butoxycarbonyl) -A- (N,N- dibenzylamino) methyl pyroglutamate .

A solution of 1.08 g (4.20 mmol) of N-BOC-ethyl-D- pyroglutamate in 40 mL of dry THF was cooled to -78 ²C under nitrogen atmosphere. To this solution, 4.20 ml (4.2 mmol) of LHDMS were added dropwise. The mixture was stirred at -78 ^aC for 45 min and then cooled to -95 ^aC. 1.40 g (4.20 mmol) of N, N-dibenzyl-N-methylene ammonium iodide (prepared as described in: Bryson, T. A.; Bonitz, G. H. ; Reichel, C. J. ; Dardis, R. E. J^". Org. Chem. 1980, 45, 524-525) were added in one portion. The reaction mixture was stirred at -95 ^aC for lh and at -78 ^aC overnight, quenched with saturated aqueous ΝH₄C1 and extracted with ether. The organic layer was washed with water and brine and dried over Na₂S0₄. Concentration afforded an oil that was purified by column chromatography using Hex/Et₂0/triethylamine (2:1:0.05) to yield 530 mg (27 %) of a white solid which have a ^XH NMR consistent with structure, mp 71-72 ^aC. STEP 16B. Ethyl (22?, 42?) -1- (tert-butoxycarbonyl) -4- aminomethyl pyroglutamate .

10% Pd-C (530 mg, 0.5 mmol) was added to a solution of ethyl (22?, 42?) -2-tertbutoxy carbonyl-4- (N, N-dibenzylamino) methyl pyroglutamate (510 mg, 1.09 mmol) in MeOH (60 ml). The solution was saturated with H₂ and stirred under a positive H₂ atmosphere (rubber balloon) overnight. The reaction mixture was filtered through a pad of celite and concentrated to afford a colorless oil (0.31 g, 99%) which gave a ^XH ΝMR consistent with structure.

STEP 16C. Ethyl (22?, 42?) -1- (tert-butoxycarbonyl) -4- (Ν- benzoylamino) methyl pyroglutamate . To a solution of ethyl (22?, 42?) -1-tertbutoxy carbonyl-4- aminomethyl pyroglutamate (170 mg, 0.59 mmol) in CH₂C1₂ (10 ml) was added benzoyl chloride (75.5 ml, 0.65 mmol), triethylamine (246 ml, 1.77 mmol), and a catalytic amount of N, N-dimethyl-4-aminopyridine . The solution was stirred at room temperature until TLC shows the absence of starting material (4.25 h) and then it was concentrated to dryness under vacuum. The residue was slurried in ether and washed with a saturated solution of ΝH₄CI in water three times and then with brine. The organic layer was dried over Na₂Sθ₄, concentrated and the residue purified by column chromatography (Hex/EtOAc 1:2). The product was obtained as a colorless oil (160 mg, 69 %) having a ^XH NMR consistent with structure.

STEP 16D.

( 22?, 42?) -2-Amino-4- (N-benzoylamino) methyl pentanedioic acid was prepared in a manner analogous to that described for Example 1 , Step ID . White solid . 9% . mp 182-183 °C . [α] _D ²⁰= -37 . 9 (c 0 . 43 , IN HCl) . ^XH-NMR (D₂0/Pyridine-d₅) : 7 . 79-7 . 14 ( , 5H) , 3.51 (m, IH) , 3.25-3.19 (m, 2H) , 2.64-2.24 (m, IH) , 1.92-1.76 (m, 2H) . ¹³C-NMR (D₂0) : 182.3, 181.6, 170.5, 133.5, 131.7, 128.4, 126.7, 54.2, 45.3, 42.2, 35.9.

EXAMPLE 17.

(22?, 45) -2-Amino-4- (in-iodo) benzyl pentanedioic acid.

STEP 17A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (m- iodo) benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using m- iodobenzyl bromide as reagent. ^XH NMR consistent with structure. 66%. White solid, mp 91-93 °C .

STEP 17B.

(22?, 45) -2-Amino-4- (m-iodo) benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. 45%. White solid, mp 148-149 ^aC. ^XH-NMR

(D₂0/K0D) δ 7.63-7.54 (m, 2H) , 7.24 (brdd, J^" = 6.3 and 1.4 Hz, IH) , 7.06 (brt, J^" = 7.7 Hz, IH) , 4.00 (dd, J^" = 8.4 and 5.5 Hz, IH) , 3.03-2.82 (m, 3H) , 2.29 (m, IH) , 1.94 (m, IH) . ¹³C-NMR (D₂0/K0D/Me0H-d) : 184.2, 183.7, 144.0, 138.7, 136.1 131.3, 129.3, 94.9, 55.7, 49.2, 39.6, 39.5.

EXAMPLE 18.

(22?, 45) -2-Amino-4- (p-iodo) benzyl pentanedioic acid.

STEP 18A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (p- yodo) benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using p- iodobenzyl bromide as reagent. ¹H NMR consistent with structure. 72%. White solid, mp 130-132 °C .

STEP 18B. (22?, 45) -2-Amino-4- (p-iodo) benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. 25%. White solid, mp 139-140 ^aC. NMR data consistent with _. structure.

EXAMPLE 19.

(22?, 45) -2-Amino-4-{.m- [p- (1-chloroethyl) phenyl] benzyl} pentanedioic acid.

STEP 19A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- [m- (p- vinyl) phenyl] benzyl pyroglutamate .

The starting Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -m-iodo- benzyl pyroglutamate (1.5 mmol, prepared as described in Step 17A) was dissolved in 30 ml of a mixture Tol/EtOH 20:1 and the solution degassed for 15 min with N₂. Then, p- vinylphenyl boronic acid (2.0 equiv) was added followed by 3 ml of 2N solution of NaC0₃ and 10 mol% of Pd(Ph₃P)₄. The slurry mixture is vigorously stirred and placed in a preheated (120 °C) oil bath and heated to reflux for 4 hours (or until TLC of the mixture showed complete conversion of the starting pyroglutamate) . The reaction mixture was then cooled to room temperature, diluted with water (30 ml) and Et0 (40 ml) and the aqueous phase was extracted with Et₂0 (4 x 10 ml) . The combined organic layers were washed with water (15 ml) and brine (20 ml) , dried over MgS0₄ and evaporated in vacuo. This procedure yielded a crude material which was purified by silica gel chromatography using the appropriate eluent to af ord pure biaryl coupling product . 65%. X NMR (CDC1₃) : 7.57-7.25 (m, 7H) , 7.16 (brd, J^" = 7.4 Hz, IH) , 6.75 (dd, J = 17.3 and 10.8 Hz, IH) , 5.79 (dd, J = 17.3 and 0.9 Hz, IH) , 5.30 (dd, J = 10.8 and 0.9 Hz, IH) , 4.48 (dd, J" = 7.6 and 2.8 Hz, IH) , 4.18 (q, J = 7.1 Hz, 2H) , 3.35 (dd, ^" = 13.6 and 3.8 Hz) , 2.96 (ddd, J = 19 . A , 9.4 and 3.9 Hz, IH) , 2.72 (dd, J = 13.5 and 9.4 Hz, IH) , 2.06 (m, 2H) , 1.50 (brs, 9H) , 1.25 (td, J = 7.1 and 1.1 Hz, 3H) .

STEP 19B.

(22?, 45) -2-Amino-4-{.Ή- [p- (1-chloroethyl) henyl] benzyl} pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. In this three step process, it was observed HCl addition to the vinyl group when the hydrochloride salt was formed as a mixture of epimers in the methine benzylic carbon. 35%. White solid, mp 118-119 ^aC. ^XH-NMR (D₂0/K0D) δ 7.31 (brd, J = 8.2 Hz, IH) , 7.26-7.07 (m, 6H) , 6.94 (brd, J^" = 6.9 Hz, IH) , 2.91 (dd, J = 9.6 and 4.1 Hz, IH) , 2.59-2.36 ( , 4H) , 1.61 (m, IH) , 1.25 (m, IH) , 1.15 (d, J = 6.5 Hz, 3H) . ¹³C-NMR (D₂0/ROD/MeOH-d₄) mixture of diastereomers: 183.7, 183.0, 144.6, 141.4, 140.3, 140.1, 139.8, 136.7, 129.2, 128.3, 127.5, 127.2, 126.9, 126.3, 124.8, 69.6, 69.5, 54.9, 49.0, 48.9, 48.4, 39.2, 38.3, 23.8.

EXAMPLE 20.

(22?, 45) -2-Amino-4- [m- (2-benzo [b] thienyl) ]benzyl pentanedioic acid.

STEP 20A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [m- (2- benzo [b] thienyl) ] benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using 2-benzothienyl boronic acid as reagent. 91%. White solid. ^XH NMR (CDC1₃) : 7.85-7.75 (m, 2H) , 7.66-7.51 (m, 3H) , 7.40-7.25 (m, 3H) , 7.16 (brd, J^" = 7.6 Hz, IH) , 4.50 (dd, J = 7.9 and 3.3 Hz, IH) , 4.18 (q, J = 7.1 Hz, 2H) , 3.35 (dd, J = 13.7 and 4.0 Hz, IH) , 2.97 (ddd, J = 18.4, 9.0 and 4.0 Hz) , 2.72 (dd, - = 13.7 and 9.4 Hz , IH) , 2.08 (m, 2H) , 1.50 (s, 9H) , 1.25 (t, J = 7.1 Hz, 3H) .

STEP 2OB.

(22?, 45) -2-Amino-4- [m- (2-benzo [b] thienyl) ] benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. 81%. White solid, mp 222-223 ^aC. [α]_D= -10.6 (c 0.23, IN HCl). ^XH-NMR (D₂0/K0D) δ 7.04-6.63 (m, 9H) , 2.92 (m, IH) , 2.59-2.25 (m, 3H) , 1.74 (m, IH) , 1.20 (m, IH) . ^X3C-NMR (D₂0/K0D/Me0H-d₄) : 184.1, 183.5, 144.6, 142.2, 141.4, 139.9, 134.6, 134.6, 129.8, 127.4, 125.3, 125.2, 124.8, 124.5, 123.0, 120.4, 55.8, 49.1, 40.2, 39.9.

EXAMPLE 21.

(22?, 45) -2-Amino-4- [p- (p-methoxy) phenyl] benzyl pentanedioic acid, hydrochloride salt.

STEP 21A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (p- methoxy) phenyl] benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate (Step 18A) and p-methoxyphenyl boronic acid as reagent. 69%. White solid, mp 149-151 °C . [α]_D= +22.4 (c 0.9, CHC1₃) . ^XH NMR (CDC1₃): 7.45 (dd, J = 8.4 and 4.9 Hz, 4H) , 7.21 (m, 2H) , 6.94 (dd, J= 9.2 and 2.4 Hz, 2H) , 4.46 (dd, J = 8.1 and 2.9 Hz, IH) , 4.15 (q, J^" = 7.1 Hz, 2H) , 3.82 (s, 3H) , 3.27 (dd, J = 13.6 and 3.5 Hz, IH) , 2.92 (m, IH) , 2.67 (dd, J^" = 13.6 and 8.1 Hz, IH) , 2.10-2.00 (m, 2H) , 1.47 (s, 9H) , 1.23 (t, J^" = 7.1 Hz, 3H) . STEP 2 IB .

(22?, 45) -2-Amino-4- [p- (p-methoxy) phenyl] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure stopped in the HCl salt formation. 81%. White solid, mp 215-216 ^aC. ^XH-NMR (Me0H-d₄) δ 7.52 (d, J = 8.6 Hz, 4H) , 7.30 (d, J = 7.5 Hz, 2H) , 7.00 (d, J = 8.6 Hz, 2H) , 4.02 (dd, J = 1 . A and 4.5 Hz, IH) , 3.80 (s, 3H) , 3.20- 2.92 (m, 3H) , 2.45-2.26 (m, IH) , 2.05-1.80 (m, IH) .

EXAMPLE 22.

(22?, 45) -2-Amino-4- [p- (m-chloro) phenyl] benzyl pentanedioic acid.

STEP 22A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (m- chloro) phenyl]benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( tert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and m- chlorophenyl boronic acid as reagent. 78%. White solid, mp 99-100 °C. ^XH NMR (CDCl₃) : 7.41 (m, 8H) , 4.48 (dd, J = 7.4 and 2.7 Hz, IH) , 4.19 (q, J^" = 7.1 Hz , 2H) , 3.30 (dd, J = 13.7 and 3.5 Hz, IH) ,. 2.94 (dq, J^" = 9.3 and 3.7 Hz, IH) ,

2.71 (dd, J = 13.7 and 9.3 Hz, IH) , 2.10-2.00 (m, 2H) , 1.50 (s, 9H) , 1.24 (t, J = 7.1 Hz, 3H) .

STEP 22B. (22?, 45) -2-Amino-4- [p- (m-chloro) phenyl] benzyl pentanedioic acid, was prepared in a manner analogous to that described for Example 1, Step ID. 78%. White solid, mp 151-153 ^aC. ^XH- NMR (MeOH-d₄/KOD) δ 7.65-7.48 (m, 4H) , 7.46-7.24 (m, 4H) , 3 . 06 ( , IH) , 2 . 85-2 . 60 (m, 3H) , 2 . 24-2 . 00 (m, IH) , 1 . 64- 1 . 43 ( , IH) .

EXAMPLE 23 . (22?, 45) -2-Amino-4- [p- (p-chloro) phenyl] benzyl pentanedioic acid, hydrochloride salt.

STEP 23A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (p- chloro) phenyl] benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and p- chlorophenyl boronic acid as reagent. 74%. White solid, mp 147-151 °C. ^XH NMR (CDC1₃) : 7.50-7.20 ( , 8H) , 4.48 (dd, J = 8.2 and 1.4 Hz, IH) , 4.22 (q, J = 7.1 Hz, 2H) , 3.30 (dd, J = 13.6 and 4.4 Hz, IH) , 3.00-2.85 ( , IH) , 2.71 (dd, J = 13.6 and 9.6 Hz, IH) , 2.06 (dt, J^" = 9.5 and 1.4 Hz, 2H) , 1.50 (s, 9H) , 1.26 (t, J^" = 7.1 Hz, 3H) .

STEP 23B,

(22?, 45) -2-Amino-4- [p- (p-chloro) phenyl] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 85%. White solid, mp 214 ²C (dec). ^XH-NMR (MeOH-d₄/KOD) δ 7.83 (t, J = 8.4 Hz, 2H) , 7.64 (m, 2H) , 7.36 (dd, J = 8.3 and 2.5 Hz, 4H) , 3.29 (m, IH) , 3.03 ( , IH) , 2.74 (dd, J = 15.6 and 7.0 Hz, 2H) , 2.11 (m, IH) , 1.55 ( , IH) .

EXAMPLE 24.

(22?, 45) -2-Amino-4- [p- (3-thienyl) Jbenzyl pentanedioic acid, hydrochloride salt . STEP 24A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (3- thienyl) ] benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and 3-thienyl boronic acid as reagent. 55%. White solid, mp 200-201 °C . H NMR (CDC1₃) : 7.50 (d, J= 8.1 Hz, 2H) , 7.37 (m, 3H) , 7.18 (d, J = 8.1 Hz, 2H) , 4.46 (dd, J = 7.8 and 3.1 Hz, IH) , 4.16 (q, J^" = 7.1 Hz, 2H) , 3.26 (dd, J = 13.6 and 3.8 Hz, IH) , 2.91 (dq, J = 7.6 and 3.8 Hz, IH) , 2.67 (dd, J = 13.6 and 9.1 Hz, IH) , 2.04 (m, 2H) , 1.45 (s, 9H) , 1.23 (t, J = 7.1 Hz, 3H) .

STEP 24B.

(22?, 45) -2-Amino-4- [p- (3-thienyl) ] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, 'Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 98%. White solid, mp 186-187 ^aC. ^XH-NMR (MeOH-d₄/KOD) δ 7.65 (m, 3H) , 7.48 (m, 2H) , 7.32 (d, J = 7.3^' Hz, 2H) , 4.03 (dd, J = 8.6 and 5.7 Hz, IH) , 3.20-2.90 (m, 3H) , 2.41 (m, IH) , 2.05-1.90 ( , IH) .

EXAMPLE 25.

(22?, 45) -2-Amino-4- [p- (p-fluoro) phenyl] benzyl pentanedioic acid, hydrochloride salt.

STEP 25A. Ethyl ( 2R, AS) -1- (tert-butoxycarbonyl) -4- [p- (p- fluoro) phenyl] benzyl pyroglutamate.

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( tert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and p- fluorophenyl boronic acid as reagent. 81%. White solid, mp 129-130 °C. ^XH NMR (CDC1₃) : 7.50-7.36 (m, 4H) , 7.18 (apparent d, J = 6.9 Hz, 2H) , 7.05 (dt, J = 8.7 and 1.5 Hz , 2H) , 4.44 (dd, J = 8.1 and 2.8 Hz, IH) , 4.13 (q, J = 7.1 Hz, 2H) , 3.24 (dd, J = 13.6 and 3.7 Hz, IH) , 2.89 (dq, J = 9.1 and 4.5 Hz, IH) , 2.67 (dd, J = 13.6 and 9.2 Hz, IH) , 1.98 (m, 2H) , 1.45 (s, 9H) , 1.21 (t, J^" = 7.1 Hz, 3H) .

STEP 25B. (22?, 45) -2-Amino-4- [p- (p-fluoro) phenyl] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 54%. White solid, mp 162-163 ²C . ^XH-NMR (MeOH-d₄) δ 7.55 (m, 2H) , 7.50 (d, J = 6.7 Hz, 2H) , 7.30 (d, J = 6.7 Hz, 2H) , ^■7.10 (t, J- = 10.0 Hz, 2H) , 4.00 (dd, J = 8.2 and 5.5 Hz, IH) , 3.15-2.80 (m, 3H) , 2.41-2.23 (m, IH) , 2.05-1.82 (m, IH) .

EXAMPLE 26.

(22?, 45) -2-Amino-4- [p- (2-naphtyl) Jbenzyl pentanedioic acid, hydrochloride salt .

STEP 26A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (2- naphthyl) ] benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and 2-naphthyl boronic acid as reagent. 52%. White solid, mp 172-174 °C . ^XH NMR (CDCI3) : 8.04 (brs, IH) , 7.90 (m, 3H) , 7.78 (dd, J = 9.1 and 1.5 Hz, IH) , 7.67 (d, J = 8.1 Hz, 2H) , 7.50 (t, J = 3.7 Hz, 2H) , 7.30 (d, ,7 = 8.1 Hz, 2H) , 4.52 (dd, J = 8.1 and 2.8 Hz, IH) , 4.21 (q, J = 7.1 Hz, 2H) , 3.35 (dd, J = 13.7 and 4.0 Hz, IH) , 2.98 (dq, J = 9.3 and 4.6 Hz , IH) , 2.75 (dd, J = 13.7 and 9.3 Hz, IH) , 2.13 (dd, J = 17.0 and 5.9 Hz, IH) , 2.12 (dd, J = 17.3 and 6.3 Hz, IH) , 1.53 (s, 9H) , 1.28 (t, J = 7.1 Hz, 3H) .

STEP 26B.

(22?, 45) -2-Amino-4- [p- (2-naphthyl) ] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 100%. White solid, mp 175-176 ^aC . ^XH-NMR (MeOH-d) : 8.11 (s, IH) , 7.94 (m, 3H) , 7.77 (t, J = 8.7 Hz, 3H) , 7.52 (dd, J = 3.7 and 1.3 Hz, 2H) , 7.41 (d, J = 6.8 Hz, 2H) , 4.61 (t, J = 6.2 Hz, IH) , 3.40-2.90 (m, 3H) , 2.37 (m, IH) , 2.04 (m, IH) .

EXAMPLE 27.

(22?, 45) -2-Amino-4- [p- (2-benzo [b] thienyl) ] benzyl pentanedioic acid, hydrochloride salt.

STEP 27A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (2- benzo [b] thienyl) ] benzyl pyroglutamate. The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and 2- benzo [b] thienyl boronic acid as reagent. NMR data consistent with structure. 81%. White solid, mp 173-175 °C . [α]_D= +18.9 (c 0.9, CHC1₃) . X NMR (CDCI3) : 7.70 (m, 2H) , 7.55 (d, J = 8.3 Hz, 2H) , 7.43 (brs, IH) , 7.24 (dt, J = 9.2 and 1.8 Hz, 2H) , 7.14 (d, J^" = 8.9 Hz, 2H) , 4.40 (dd, J^" = 8.3 and 2.7 Hz, IH) , 4.10 (q, J = 7.1 Hz, 2H) , 3.21 (dd, J = 13.7 and 4.0 Hz , IH) , 2 . 87 ( , IH) , 2 . 63 ( dd, J^" = 13 . 7 and 9 . 1 Hz , IH) , 1 . 98 (m, 2H) , 1 . 41 ( s , 9H) , 1 . 17 ( t , J = 7 . 1 Hz , 3H) .

STEP 27B . (22?, 45) -2-Amino-4- [p- (2-benzo [b] thienyl) ]benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 67%. White solid, mp 250 ^aC (dec). ^XH-NMR (MeOH-d₄) : 7.82 (dt, J^" = 7.6 and 1.4 Hz, 2H) , 7.71 (dd, J = 8.1 and 1.3 Hz, 2H) , 7.64 (s, IH) , 7.34 (m, 4H) , 4.07 (t, J = 6.1 Hz , IH) , 3.20-2.90 (m, 3H) , 2.40 (m, IH) , 2.00 (m, IH) .

EXAMPLE 28. (22?, 45) -2-Amino-4- [m- (m-amino) phenyl] benzyl pentanedioic acid.

STEP 28A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [m- (m- amino) phenyl] benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -m-iodo-benzyl pyroglutamate as starting material (Step 17A) and m-amino phenyl boronic acid, hydrochloride salt, as reagent. 83%. Yellowish solid. [α]_D= +16.5 (c 0.91, CHC1₃) . X NMR (CDC1₃) : 7.44-7.10 (m, 5H) , 6.93 (dd, J^" = 7.6 and 0.8 Hz, IH) , 6.88 (brd, J = 1.9 Hz, IH) , 6.64 (dd, J = 7.8 and 1.3 Hz, IH) , 4.46 (dd, ^" = 7.4 and 3.9 Hz , IH) , 4.17 (q, J = 7.1 Hz, 2H) , 3.78 (brs, 2H) , 3.32 (dd, J = 13.6 and 4.0 Hz, IH) , 2.95 (ddd, J = 20.0, 9.2 and 4.0 Hz, IH) , 2.69 (dd, J = 13.6 and 9.4 Hz, IH) , 2.05 (m, 2H) , 1.49 (s, 9H) , 1.24 (t, J = 7.1 Hz, 3H) . STEP 28B .

(22?, 45) -2-Amino-4- [m- (m-amino) phenyl] benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. 10%. Yellowish solid, mp 80-83 ^aC. ^XH-NMR (D₂0/K0D) : 7.65-7.35 (m, 5H) , 6.97 (m, 2H) , 6.76 ( , IH) , 3.23 (m, IH) , 2.99 (m, IH) , 2.71 (m, 2H) , 2.03 ( , IH) , 1.23 (m, IH) .

EXAMPLE 29.

(22?, 45) -2-Amino-4- [p- (p-methylthio) phenyl] benzyl pentanedioic acid, hydrochloride salt.

STEP 29A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (p- methylthio) phenyl] benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and p- ethylthiophenyl boronic acid as reagent. 83%. Pale cream solid, mp 149-150 °C . ^XH NMR (CDCl₃) : 7.44 (dd, J^" = 8.3 and 1.9 Hz, 4H) , 7.22 (dd, J = 13.4 and 8.2 Hz , 4H) , 4.44 (dd, J = 7.9 and 3.1 Hz, IH) , 4.14 (q, J^" = 7.1 Hz, 2H) , 3.24 (dd, J = 13.7 and 3.9 Hz, IH) , 2.91 (dq, J = 9.1 and 3.9 Hz, IH) , 2.66 (dd, J = 13.7 and 9.1 Hz, IH) , 2.45 (s, 3H) , 2.04 (m, 2H) , 1.45 (s, 9H) , 1.21 (d, J = 7.1 Hz, 3H) .

STEP 29B.

(22?, 45) -2-Amino-4- [p- (p-methylthio) phenyl] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation.^' 58%. White solid, mp 229-230 ^aC . ^XH-NMR (MeOH-d₄) : 7.53 (t, J= 6.6 Hz, 4H) , 7.34 (d, J= 7.8 Hz, 4H) , 3.27 (m, IH) , 3.03 (dt, J = 9.3 and 2.5 Hz, IH) , 2.72 (d, ^" = 5.2 Hz, 2H) , 2.54 (s, 3H) , 2.10 (ddd, J = 13.6, 3.6, 1.7 Hz, IH) .

EXAMPLE 30.

(22?, 45) -2-Amino-4- [p- (m-amino) phenyl] benzyl pentanedioic acid, hydrochloride salt.

STEP 30A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- [p- [m- amino) phenyl] benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and m- aminophenyl boronic acid, hydrochloride salt, as reagent.

Yellowish syrup. [α]_D= +31.6 (c 1.0, CHC1₃) . ^XH NMR (CDC1₃) : 7.47 (dd, ^" = 8.1 and 1.3 Hz, 2H) , 7.23-7.15 (m, 3H) , 6.94 (dd, J = 7.7 and 1.0 Hz, IH) , 6.87 (t, J - 1.7 Hz , IH) , 6.84 (dd, J^" = 7.8 and 1.4 Hz, IH) , 4.48 (dd, J = 7.9 and 3.3 Hz, IH) , 4.18 (q, J = 7.1 Hz, 2H) , 3.80 (brs, 2H) , 3.27 (dd, J = 13.7 and 3.9 Hz, IH) , 2.94 (dq, J = 9.4 and 3.7 Hz, IH) , 2.69 (dd, J^" = 13.7 and 9.3 Hz, IH) , 2.00 (m, 2H) , 1.50 (s, 9H) , 1.25 (t, J^" = 7.1 Hz, 3H) .

STEP 30B.

(22?, 45) -2-Amino-4- [p- (m-amino) phenyl] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. 50%. Yellowish solid, mp 98-99 ^aC . ^XH-NMR (MeOH-d₄) : 7.78 (dd, J = 7.9 and 1.2 Hz, IH) , 7.70-7.62 (m, 4H) , 7.42 (m, 3H) , 4.08 (dd, J = 7.4 and 4.5 Hz, IH) , 3.20-2.90 (m, 3H) , 2.46-2.28 (m, IH) , 2.08-1.91 (m, IH) . EXAMPLE 31 .

(22?, 45) -2-Amino-4- [p- (m-nitro) phenyl] benzyl pentanedioic acid.

STEP 31A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- ( - nitro) phenyl] benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and m-nitro phenyl boronic acid, as reagent. 71%. mp 194-196 °C. Yellowish solid. [α]_D= +27.1 (c 0.5, CHC1₃) . X NMR (CDC1₃) : 8.38 (q, J = 2.1 Hz, IH) , 8.14 (brd, J = 8.8 Hz, IH) , 7.86 (dq, - = 8.8 and 1.1 Hz , IH) , 7.59 (dd, J^" = 8.8 and 1.4 Hz, IH) , 7.53 (dd, J = 8.1 and 1.4 Hz, IH) , 7.27 (dd; J^" = 8.8 and 1.9 Hz, 2H) , 4.47 (dd, J^" = 8.0 and 2.8 Hz, IH) , 4.16 (q, J = 7.3 Hz, 2H) , 3.28 (dd, J = 13.7 and 3.9 Hz, IH) , 2.93 (dq, J^" = 9.1 and 2.3 Hz, IH) , 2.73 (dd, J = 12.7 and 9.2 Hz, IH) , 2.08 (m, 2H) , 1.49 (s, 9H) , 1.21 (t, J = 7.3 Hz, 3H) .

STEP 3IB.

(22?, 45) -2-Amino-4- [p- (m-nitro) henyl] benzyl pentanedioic acid, was prepared in a manner analogous to that described for Example 1, Step ID. Yellowish solid. NMR data consistent with structure.

EXAMPLE 32.

(22?, 45) -2-Amino-4- [p- (2-benzo [b] furyl) ]benzyl pentanedioic acid, hydrochloride salt.

STEP 32A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (2- benzo [b] furyl) ] benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 19, Step 19A, using Ethyl (22?, 45) -1- ( ert-butoxycarbonyl) -p-iodo-benzyl pyroglutamate as starting material (Step 18A) and 2- benzo [b] furyl boronic acid, as reagent. 76%. mp 159-160 °C (dec). White solid. [α]_D= +22.5 (c 0.7, CHC1₃) . ^XH NMR (CDC1₃) : 8.07 (d, J^" = 8.1 Hz , 2H) , 7.82 (dd, J = 11.7 and 8.3 Hz, 2H) , 7.53 (dd, J = 5.3 and 2.8 Hz, 4H) , 7.27 (brs, IH) , 4.47 (dd, J^" = 8.3 and 2.8 Hz , IH) , 4.17 (q, J = 7.1 Hz , 2H) , 3.27 (dd, J^" = 13.6 and 3.9 Hz , IH) , 2.92 (dq, J = 9.3. and 4.6 Hz, IH) , 2.70 (dd, J = 13.6 and 9.2 Hz, IH) , 2.02 (dt, J = 8.5 and 2.5 Hz, 2H) , 1.49 (s, 9H) , 1.24 (t, J^" = 7.1 Hz, 3H) .

STEP 32B.

(22?, 45) -2-Amino-4- [m- (2-benzo [b] furyl) ]benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 250 °C (dec) . NMR data consistent with structure.

EXAMPLE 33.

(22?, 45) -2-Amino-4- [p- (N,N-diethylamino) ]benzyl pentanedioic acid, hydrochloride salt.

STEP 33A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (p- nitro) benzyl pyroglutamate.

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using p-nitrobenzyl bromide as reagent. NMR data consistent with structure. 70%. White solid. STEP 33B. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (N,N- diethylamino) ] benzyl pyroglutamate.

To a solution of the starting nitro compound (step 33A, 1.30 mmol) in 20 ml of CH₃CN was added ammonium formate (NH₄C0₂H, 8 equiv) followed by 10% Pd/C (20 mol% of catalyst) . The resulting mixture was heated to reflux for 6 hours and then cooled to rt, filtered through a short pad of Celite and the solvents evaporated in vacuo to afford a crude oil. After purification by silica gel chromatography (Hex/EtOAc, 3:1), the N,N-diethylamino derivative was obtained in 88% yield along with a minor amount of the corresponding N-ethylamino compound (17%). ^XH NMR (CDC1₃) : 6.99 (brd, J = 8.2 Hz, 2H) , 6.59 (brd, J = 8.2 Hz, 2H) , 4.43 (dd, J = 7.4 and 3.5 Hz, IH) , 4.16 (q, J = 7.1 Hz, 2H) , 3.30 (q, J^" = 7.0 Hz, 4H) , 3.12 (dd, J = 13.7 and 3.8 Hz, IH) , 2.84 (ddd, J = 19.3, 9.2 and 3.8 Hz, IH) , 2.56 (dd, J = 14.0 and 9.4 Hz), 2.04 (m, 2H) , 1.48 (brs, 9H) , 1.24 (td, J = 7.1 and 1.3 Hz, 3H) , 1.13 (td, J = 7.0 and 9.0 Hz, 6H) .

STEP 33C.

(22?, 45) -2-Amino-4- [p- (N,N-diethylamino) ]benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 10, Step 10B. 39%. mp 77-78

°C. [α]_D= -23.1 (c 0.473, MeOH). NMR data consistent with structure.

EXAMPLE 34.

(22?, 45) -2-Amino-4- [p- (N-benzenesulfonyla ino) ]benzyl pentanedioic acid, hydrochloride salt.

STEP 34A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (p- a ino) benzyl pyroglutamate . To a solution of the starting nitro compound (Step 33A, 4.30 mmol) in 90 ml of EtOH was added ammonium formate (NH₄C0₂H, 4 equiv) followed by 10% Pd/C (5 mol% of catalyst) . The resulting mixture was heated to reflux for 2 hours and then cooled to rt, filtered through a short pad of Celite and the solvents evapoated in vacuo to afford a crude oil. After purification by silica gel chromatography (Hex/EtOAc, 3:1), the aminobenzylpyroglutamate ethyl ester derivative was obtained in quantitative yield, mp 139-141 °C . [α]_D= +43.3 (c 0.32, CHC1₃) . ^XH NMR (CDC1₃) : 6.95 (brd, J= 8.3 Hz, 2H) , 6.61 (brd, J = 8.3 Hz, 2H) , 4.44 (dd, J^" = 7.4 and 4.0 Hz, IH) , 4.18 (q, ^" = 7.1 Hz, 2H) , 3.49 (brs, 2H) , 3.13 (dd, J^" = 13.8 and 4.1 Hz, IH) , 2.93-2.77 (m, IH) , 2.59 (dd, J = 13.8 and 9.0 Hz, IH) , 2.05-1.96 (m, 2H) , 1.49 (s, 9H) , 1.25 (t, J = 7.1 Hz, 3H) .

STEP 34B. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (N- benzenesulfonylamino) ] benzyl pyroglutamate.

To a solution of starting Ethyl (22?, 45) -1- ( ert- butoxycarbonyl) -4- (p-amino) benzyl pyroglutamate (0.83 mmol, 300 mg) in 10 ml of anhydrous CHC1₂ and cooled to 0 °C was added benzenesulfonyl chloride (1.1 equiv) followed by Et₃N (2.0 equiv) and a catalytic amount of DMAP (10 mol%) . The reaction mixture was warmed up to rt and the stirred for 45 minutes. The solution was diluted with CH₂C1₂ and H₂0, and the aqueous phase extracted with CH₂Cl₂. The combined organic layers were washed with IN HCl, water and brine. After drying over MgS0₄, evaporation of the solvent afforded a solid which was purified by silica gel chromatography (Hex/EtOAc, 3:1) to afford a pure white foamy solid (400 mg) . 96%. mp 78-80 °C. [α]_D= +7.0 (c 0.43, CHC1₃) . ^XH NMR (CDC1₃) : 7.96-7.90 (m, 2H) , 7.73-7.50 (m, 4H) , 7.17 (brd, J = 8.4 Hz, 2H) , 6.95 (dd, J^" = 8.5 and 2.0 Hz, 2H) , 4.51 (dd, J^" = 9.0 and 2.0 Hz, IH) , 4.22 (q, J = 7.1 Hz, 2H) , 3.29 (dd, J = 13.8 and 4.0 Hz, IH) , 2.91 (m, IH) , 2.69 (dd, J = 13.8 and 9.2 Hz, IH) , 2.13-1.98 (m, 2H) , 1.50 (s, 9H) , 1.28 (t, J = 7.1 Hz, 3H) .

STEP 34C.

(22?, 45) -2-Amino-4- [p- (N-benzenesulfonylamino) ] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid. 65%. mp 113-114 °C. [α]_D= -14.0 (c 0.55, MeOH). ^XH-NMR (MeOH-d ) : 7.83-7.54 (m, 5H) , 7.26 (brd, J^" = 8.2 Hz, 2H) , 6.91 (brd, J- = 6.9 Hz, 2H) , 4.03 (brt, J = 7.1 Hz, IH) , 3.00 (m, 3H) , 2.32 (m, IH) , 1.98 (m, IH) . ^X3C-NMR (MeOH-d₄) : 176.8, 171.4, 142.5, 140.5, 135.4, 133.9, ^"132.8, 131.0, 130.2, 129.5, 52.5, 44.2, 38.6, 33.1.

EXAMPLE 35.

(22?, 45) -2-Amino-4- [p- (N-dansylamino) ] benzyl pentanedioic acid, hydrochloride salt.

STEP 35A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (N- dansyla ino) ] benzyl pyroglutamate. To a solution of starting Ethyl- (22?, 45) -1- ( ert- butoxycarbonyl) -4- (p-amino)benzylpyroglutamate (Step 34A, 4.69 mmol, 1.7 g) in 55 ml of anhydrous THF and cooled to - 78 °C, dansyl chloride (5- (N,N-dimethylamino) -1- naphthalenesulfonylchloride, (1.1 equiv, 1.39 g) was added followed by Et₃N and, finally, a catalytic amount of DMAP

(15 mol%) . The resulting mixture was stirred for 1 h at -78 °C and for an additional hour at room temperature. The solution was evaporated in vacuo and the residue diluted with CH₂C1₂ and H₂0, and the aqueous phase extracted with CHC1₂. The combined organic layers were washed with IN HCl, water and brine. After drying over MgS0₄, evaporation of the solvent afforded a yellow solid which was purified by silica gel chromatography (Hex/EtOAc, 3:1) to afford a pure brilliant yellowish foamy solid (590 mg) . A large amount of starting material was recovered from the aqueous phase. Yield: 21%. ^XH NMR (CDC1₃) : 8.50 (brd, J = 8.5 Hz, IH) , 8.35 (brd, J = 8.7 Hz, IH) , 8.18 (dd, J = 7.3 and 1.3 Hz, IH) , 7.55 (dd, J = 8.6 and 7.6 Hz, IH) , 7.44 (dd, J^" = 8.6 and 7.4 Hz, IH) , 7.29 (brs, IH) , 7.17 (dd, J = 6.9 and 0.6 Hz, IH) , 6.89 (AB system, 4H) , 4.43 (dd, J^" = 8.4 and 2.6 Hz, IH) , 4.18 (d, J = 13.8 Hz, 2H) , 3.10 (dd, J^" = 13.8 and 4.0 Hz, IH) , 2.87 (brs, 6H) , 2.79 (m, IH) , 2.52 (dd, J = 13.8 and 9.2 Hz, IH) , 1.94 (m, 2H) , 1.48 (s, 9H) , 1.25 (t, J = 7.1 Hz, 3H) .

STEP 35B.

(22?, 45) -2-Amino-4- [p- (N-dansylamino) ]benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation.

Pale cream solid. 38%. mp 190-191 °C . fα]_D= -9.9 (c 0.37, MeOH). ^XH-NMR (MeOH-d₄) : 8.93 (d, J = 8.7 Hz, IH) , 8.60 (d, J = 8.7 Hz, IH) , 8.37 (m, ^" = 6.7 Hz, IH) , 8.09 (d, J = 7.6 Hz, IH) , 7.83 (m, 2H) , 6.95 (q, J = 8.6 Hz, 4H) , 3.95 (dd, J^" = 8.5 and 7.5 Hz, IH) , 3.44 (brs, 6H) , 2.80 (m, 3H) , 2.19 (m, IH) , 1.83 (m, IH) . ¹³C-NMR (MeOH-d₄) : 176.9, 171.3,

141.0, 138.0, 137.1, 136.0, 132.4, 130.9, 130.7, 128.8,

128.1, 127.7, 127.3, 127.2, 121.8, 120.6, 58.3, 52.4, 44.3, 38.3, 34.8, 32.9.

The compound of Example 35 is fluorescent and is therefore particularly useful as a research tool, for example in high throughput screening for other glutamate racemase inhibitors . EXAMPLE 36 .

(22?, 45) -2-Amino-4- [p- (N-phenylaminocarbonyl) aminojbenzyl pentanedioic acid, hydrochloride salt.

STEP 36A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [p- (N- phenylaminocarbony1) amino] benzyl pyroglutamate . To a solution of starting Ethyl- (22?, 45) -1- ( ert- butoxycarbonyl) -4- (p-amino) benzylpyroglutamate (Step 34A, 1.0 mmol, 360 mg) in 10 ml of anhydrous CH₂C1₂ and cooled to 0 °C was added PhNCO (phenyl isocyanate, 1.1 equiv) and Et₃N (2.0 equiv) . The reaction mixture was warmed up to rt and the stirred for lh. The solution was diluted with CH₂C1₂ and H₂0, and the aqueous phase extracted with CH₂C1₂. The combined organic layers were washed with IN HCl, water and brine. After drying over MgS0₄, evaporation of the solvent afforded a colorless oil which was purified by silica gel chromatography (Hex/EtOAc, 3:1) to afford a pure colorless oil (368 mg) . 76%. X NMR (CDC1₃) : 7.84 (brd, J = 5.1 Hz, 2H) , 7.41-7.26 (m, 6H) , 7.11 (m, 3H) , 4.45 (dd, J = 7.9 and 3.1 Hz, IH) , 4.21 (qd, J = 7.1 and 1.3 Hz, 2H) , 3.08-2.69 (m, 3H) , 2.13-1.97 (m, 2H) , 1.47 (s, 9H) , 1.27 (t, J = 7.1 Hz, 3H) .

STEP 36B.

(22?, 45) -2-Amino-4- [p- (N-phenylaminocarbonyl) amino] benzyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. Pale cream solid. 38%. mp 167-168 °C . [ ]_D= -10.9 (c 1.1, MeOH). ^XH-NMR (Me0H-d₄) : 7.43-6.94 (m, 9H) , 3.94 (m, IH) , 2.77-3.05 ( , 3H) , 2.27 (m, IH) , 1.87 (m, IH) . ¹³C-NMR (MeOH-d) : 177.2, 171.3, 155.5, 140.3, 138.9, 133.7, 130.5, 129.8, 123.7, 120.6, 120.3, 52.5, 44.4, 38.5, 32.6. EXAMPLE 37 .

(22?, 45) -2-Amino-4- [p- (phenyl) phenoxy] pentanedioic acid, hydrochloride salt .

STEP 37A. Methyl (22?, 42?) -4-hydroxyprolinate hydrochloride. Cis-4-hydroxy-D-proline (3 g, 23 mmol) was dissolved in a saturated HCl solution in methanol . The solution was stirred at room temperature overnight and then the solvent was evaporated obtaining a white solid (mp 89-90 ²C) . NMR data consistent with structure.

STEP 37B. Methyl (22?, 42?) -N-tert-butoxycarbonyl-O-tert- butoxycarbonyl- -hydroxyprolinate. To a solution of methyl (22?, 42?) -3-hydroxyprolinate hydrochloride (4.1 g, 22.6 mmol) in THF (100 ml) was added triethylamine (9.4 ml), DMAP (5 mg) and di- ert-butyl dicarbonate (6.33 g, 67.8 mmol). The reaction mixture was stirred at room temperature for 4 days and then the mixture was neutralized with IN HCl and extracted with dichloromethane. The crude obtained after evaporation of the solvent was purified by column chromatography (Hex/EtOAc 10:1), yield: 33%. White solid (mp 87-88 ^aC) . NMR data consistent with structure.

STEP 37C. Methyl (22?, 42?) -N- ert-butoxycarbonyl-O-tert- butoxycarbonyl-4-hydroxypyroglutamate: To a solution of methyl (22?, 42?) -N- tert-butoxycarbonyl-O-tert-butoxycarbonyl- 3-hydroxyprolinate (0.5 g, 1.4 mmol) in ethyl acetate (20 ml) was added a mixture of ruthenium dioxide (30 mg, 0.21 mmol) in a 10% sodium metaperiodate (15 ml) . The reaction mixture was stirred at room temperature for two days . The aqueous phase was washed with ethyl acetate (3 x 20 mL) and the combined organic phases were treated with isopropanol (4 ml) for 2 hours. The black precipitate was filtered and the organic solution was washed with water. The organic phase was dried (Na₂S0₄) , filtered and evaporated to dryness. The reaction crude was purified by column chromatography (Hex/EtOAc, 3:1) obtaining a white solid (quantitative yield), mp 105-106 ²C. NMR data consistent with structure.

STEP 37D. Methyl (22?, 42?) -4-hydroxypyroglutamate.

To a solution of methyl (22?, 42?) -N- ert-butoxycarbonyl -O-tert-butoxycarbonyl-3-hydroxypyroglutamate (2.2 g, 6.13 mmol) in dichloromethane (40 ml) was added trifluoroacetic acid (4.68 ml, 61.3 mmol). The reaction mixture was stirred at room temperature for 5 hours and then it was washed with a saturated NaHC0₃ solution. The organic phase was dried, filtered and evaporated to dryness to afford a solid that was purified by chromatography (ethyl acetate) , 82% yield, mp 116-117 ²C. NMR data consistent with structure.

STEP 37E. Methyl (2R, 4S) -4- [p- (phenyl)phenoxy] pyroglutamate .

To a cooled solution (0 ²C) of Methyl (22?, 42?) -4-hydroxy pyroglutamate (100 mg, 0.63 mmol), triphenylphosphine (184 mg, 0.70 mmol) and p-phenyl phenol (0.70 mmol) in THF (5 ml) was added diethylazodicarboxylate (DEAD, 0.09 ml, 0.70 mmol) . The reaction mixture was stirred at room temperature for 2 days. Then the solvent was evaporated to dryness and the crude was purified by column chromatography (Hex/EtOAc, 3:1). NMR data consistent with structure. White solid, mp 156-158 °C.

STEP 37F.

(22?, 45) -2-Amino-4- [p- (phenyl)phenoxy] pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 188-189 °C. [ ]_D = -46.3 (c 0.16, MeOH). ^XH- NMR (Methanol-d4) : 7.44 (d, J^" = 7.5 Hz, 4H) , 7.38-7.12 ( , 3H) , 6.91 (d, - = 7.5 Hz, 2H) , 5.10-4.90 (m, IH) , 4.25-4.06 (m, IH) , 2.67-2.25 (m, 2H) . ^X3C-NMR (Methanol-d4) : 158.3, 141.8, 136.4, 129.8, 129.0, 127.9, 127.6, 116.6, 110.3, 34.7.

EXAMPLE 38. (22?, 45) -2-Amino-4- [p- (phenoxy) phenoxy] pentanedioic acid, hydrochloride salt .

STEP 38A. Methyl (2R, 4S) -4- [p- (phenoxy) phenoxy] pyroglutamate . The title compound was prepared in a manner analogous to that described for Example 37, Step 37D. In this case, p- phenoxy phenol was employed as reagent. NMR data consistent with structure. White solid, mp 123-125 °C .

STEP 38B.

(22?, 45) -2-Amino-4- [p- (phenoxy) phenoxy] pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 151-153 °C. [ ]_D= -42.4 (c 0.5, MeOH). ^XH- NMR (Methanol-d4) : 7.21-7.11 (m, 3H) , 6.94-6.75 (m, 6H) , 4.80-4.60 (m, IH) , 4.25-4.02 (m, IH) , 2.61-2.33 ( , 2H) .

EXAMPLE 39.

(22?, 45) -2-Amino-4-phenoxy pentanedioic acid, hydrochloride salt. STEP 39A. Methyl (2R, 4S) -4-phenoxy pyroglutamate. The title compound was prepared in a manner analogous to that described for Example 37, Step 37D. In this case phenol was employed as reagent. NMR data consistent with structure. Colorless oil.

STEP 39B.

(22?, 45) -2-Amino-4-phenoxy pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 108-110 °C . ^XH-NMR (Methanol-d4) : 7.20-7.07 (m, 2H) , 6.88-6.77 (m, 3H) , 4.80-4.60 (m, IH) , 4.19-4.03 (m, IH) , 2.60-2.17 (m, 2H) . ¹³C-NMR (Methanol-d4) : 158.7, 130.5, 123.0, 116.2, 110.3, 34.6, 24.4, 14.7.

EXAMPLE 40.

(22?, 45) -2-Amino-4- (p-methy1) benzyl pentanedioic acid, hydrochloride salt .

STEP 40A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- (p- methyl) benzyl pyroglutamate .

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using p- methylbenzyl bromide as reagent. NMR data consistent with structure .

STEP 40B.

(22?, 45) -2-Amino-4- (p-methyl) benzyl pentanedioic acid, hydrochloride salt was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 169-170²C. 79 %. [ ]_D= -13.3(c 1.0, MeOH). ^XH NMR (MeOH-d) : 7.09 (AA'BB' system, 4H) , 3.94 (dd, J = 5.4 and 8.1 Hz, IH) , 3.31-2.80 (m, 3H) , 2.27-2.14 ( , IH) , 2.26 (s, 3H) , 1.99-1.89 (m, IH) . ^X3C-NMR (MeOH-d₄) : 177.4, 171.7, 137.3, 136.4, 130.1, 130.0, 52.6, 44.5, 38.8, 32.9, 21.2.

EXAMPLE 41.

(22?, 45) -2-Amino-4- (3-cyclohexyl)propyl pentanedioic acid.

STEP 41A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (3- cyclohexyl) propyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using cinnamyl bromide as reagent to obatined the 4-cinnamyl pyroglutamate derivative which was completely hydrogenated using H₂/Pt0₂ to afford the product bearing the saturated side chain. NMR data consistent with structure.

STEP 4IB.

(22?, 45) -2-Amino-4- ( 3-cyclohexyl) propyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 165-166 °C . ^XH NMR (Me0H-d₄) :

3.19 (dd, J = 9.5 and 3.6 Hz, IH) , 2.34-2.28 (m, IH) , 1.72- 1.05 (m, 15H) , 0.98-0.75 (m, 4H) . ¹³C-NMR (MeOH-d₄) : 184.9, 182.8, 58.3, 56.5, 41.2, 39.0, 35.6, 34.6, 27.8, 27.5, 26.4, 18.4.

EXAMPLE 42.

(22?, 45) -2-Amino-4-ethyl pentanedioic acid, hydrochloride salt. STEP 42A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4-ethyl pyroglutamate .

The title compound was prepared following a similar procedure to that described by A. Rubio et al, (J. Org.

Chem. 1995, 60, 2925 for the D-glutamic analog) : Reaction of the enolate derivative of Ethyl (22?) -1- (tert-butoxycarbonyl) pyroglutamate with acetaldehyde in the presence of boron trifluoride etherate, followed by mesylation of the derived carbinol and elimination yielded Ethyl (22?) -1- (tert- butoxycarbonyl) ethylidene pyroglutamate (85:15, E/Z mixture, 66%) . This latter was then hydrogenated (H₂/Pt0₂/EtOAc) to afford a mixture of Ethyl (22?, 42?) (major) and (22?, 45) -1- (tert-butoxycarbonyl) -4-ethyl pyroglutamate. This mixture of the 2 diastereomers was equilibrated using KCN in DMF as described by Ezquerra et al ( Tetrahedron 1993, 49, 8665) to give, after chromatographic separation, pure (22?, 45) isomer. NMR data consistent with structure.

STEP 42B.

(22?, 45) -2-Amino-4-ethyl pentanedioic acid, hydrochloride salt, was prepared in a manner analogous to that described for Example 1, Step ID. In this case the hydrolysis procedure was stopped in the HCl salt formation. White solid, mp 167-168^aC. ^XH NMR (MeOH-d₄) : 3.96 (dd, J^" = 5.6 and 8.2 Hz, IH) ; 2.61-2.50 (m, IH) ; 2.40-2.25 (m, IH) ; 1.94-1.62 (m, 3H) , 0.96 (t, J^" = 7.3 Hz, 3H) . ¹³C NMR (MeOH-d₄) : 177.8, 171.5, 52.5, 43.8, 32.8, 26.3, 11.3.

EXAMPLE 43.

(22?, 45) -2-Amino-4- (m-methyl) benzyl pentanedioic acid.

STEP 43A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- {m- methyl ) benzyl pyroglutamate . The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using m- methylbenzyl bromide as reagent. NMR data consistent with structure .

STEP 43B.

(22?, 45) -2-Amino-4- (m-methyl)benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 172-173 ²C. ^XH NMR (MeOH- d₄/KOD) : 7.12-6.91 (m, 4H) ; 3.20 (dd, J^" = 9.8 and 3.4 Hz,

IH) ; 2.90 (m, IH) ; 2.85-2.55 ( , 2H) ; 2.26 (s, 3H) , 2.09 ( , IH) ; 1.51 (m, 1H).¹³C NMR (MeOH-d₄/KOD) : 184.0, 182.9, 142.2, 138.7, 130.9, 129.1, 127.5, 127.2, 56.4, 49.7, 41.1, 40.6, 21.6.

EXAMPLE 44

(22?, 45) -2-Amino-4- [p- (benzyloxy) jbenzyl pentanedioic acid.

STEP 44A. Ethyl (2R, AS) -1- (tert-butoxycarbonyl) -4- [p- (benzyloxy) ] benzyl pyroglutamate.

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using p- benzyloxybenzyl bromide as reagent. NMR data consistent with structure.

STEP 44B.

(22?, 45) -2-Amino-4- [p- (benzyloxy) ] benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 180 ²C. [ ]_D = -29 (c 0.5, IN HCl) . ^XH NMR (MeOH-d₄/ROD) : 7.43-7.28 (m, 5H) ; 7.14 (d, J = 8.6 Hz, 2H) ; .6.92 (d, J= 8.6 Hz, 2H) ; 5.04 (s, 2H) ; 3.95 (dd, J^" = 5.4 and 8.5 Hz, IH) ; 3.02-2.78 (m, 3H) ; 2.25 (m, IH) ; 1.93 ( , IH) . ^X3C NMR (MeOH-d₄/KOD) . 177.3, 177.1, 159.1, 138.7, 131.7, 131.2, 129.4, 128.8, 128.5, 115.9, 70.9, 52.5, 44.6, 38.4, 32.7.

EXAMPLE 45. (22?, 45) -2-Amino-4- (2, 4-difluoro) benzyl pentanedioic acid.

STEP 45A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (2 , 4- difluoro) benzyl pyroglutamate.

The title compound was prepared following a similar procedure to that described for Example 1, Step IC, using 2 , 4-difluorobenzyl bromide as reagent. NMR data consistent with structure.

STEP 45B. (22?, 45) -2-Amino-4- (2, 4-difluoro) benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 152-4 ^aC. ^XH-NMR (MeOH-d/KOD) : 7.38-7.26 (m, IH) , 6.85-6.77 (m, 2H) , 3.25-3.23 (m, IH) , 2.88-2.67 (m, 3H) , 2.09 (m, IH) , 1.51 (m, IH) . ^X3C-NMR (MeOH-d₄/KOD) : 183.3, 182.8, 162.9 (dd, J^" = 243 and 12.3

Hz), 162.6 (dd, J = 243 and 12.3 Hz), 133.4, 124.9 (dd, J = 3.6 and 15.9 Hz) , 111.8 (d, J = 21 Hz) , 104.1 (t, J^" = 22 Hz), 56.3, 40.6, 33.3.

EXAMPLE 46. (22?, 45) -2-Amino-4- [m- (2-furyl) ]benzyl pentanedioic acid.

STEP 46A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- [m- (2- fury1) ]benzyl pyroglutamate . To a solution of Ethyl- (22?, 45) -4- (m-iodo) -benzyl pyroglutamate (Example 17, Step 17A, 473 mg, 1.0 mmol) and 2-furyl-tri-n-butylstannane (357 mg, 1.0 mmol) in 7 ml of anhydrous DMF under N₂, Ph₃P (21 mg, 8 mol%) is added followed by Pd₂dba₃ (18 mg, 2 mol%) . The resulting solution is heated at 60 °C for 1.5 h and then cooled to room temperature and diluted with Et0 and water (25 ml each) . The aqueous layer is extracted with Et₂0, and the organic phase washed with water, satd solution of KF, water and brine. The organic phase is dried over MgSU₄ and evaporated to afford a crude product which was purified by silica gel chromatography (in gradient, from Hex/EtOAc 20:1 to 2:1) to yield pure coupling compound as a clear oil (400 mg) . Yield: 96 %. ^XH NMR (CDC1₃) : 7.47-7.36 (m, 3H) , 7.21 (t, J= 7.6 Hz, IH) , 6.98 (dd, J = 6.2 and 1.4 Hz, IH) , 6.55 (dd, J =

3.4 and 0.6 Hz, IH) , 6.37 (dd, J = 3.4 and 1.8 Hz, IH) , 4.39 (dd, J^" = 6.9 and 4.3 Hz, IH) , 4.08 (qd, J = 7.1 and 0.6 Hz, 2H) , 3.23 (dd, J = 13.7 and 4.0 Hz , IH) , 2.85 (ddd, J^" = 18.9, 9.4 and 4.0 Hz), 2.58 (dd, J = 13.7 and 9.6 Hz , IH) , 1.95 (m, 2H) , 1.41 (s, 9H) , 1.15 (t, J = 7.1 Hz, 3H) .

STEP 46B.

(22?, 45) -2-Amino-4- [m- (2-furyl) ]benzyl pentanedioic acid was prepared in a manner analogous to that described for Example 1, Step ID. White solid, mp 134-135 ^aC. ^XH-NMR (D₂0/KOD) :

7.30 (m, 3H) , 7.11 (brt, J = 7.5 Hz, IH) , 6.92 (brd, ,7 = 6.8 Hz, IH) , 6.56 (brd, J = 3.3 Hz, IH) , 6.31 (dd, J = 3.3 and 1.6 Hz, IH) , 2.95 (brdd, J = 8.6 and 3.7 Hz, IH) , 2.59-1.74 (m, 3H) , 1.72 (m, IH) , 1.30 (m, IH) . ¹³C-NMR (D₂0/KOD/ Methanol-d₄) : 184.5, 183.7, 154.6, 143.6, 142.2, 131.5,

130.0, 129.2, 125.1, 122.4, 112.9, 106.4, 55.8, 49.2, 40.0, 39.6.

EXAMPLE 47. (22?, 45) -2-Amino-4- [ (7-methoxy) -2-naphthyl] methyl pentanedioic acid.

STEP 47A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [ (7- methoxy) -2-naphthyl] ethyl pyroglutamate . The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using 7-methoxy-2- naphtylmethyl bromide as reagent. Pale cream solid. NMR data consistent with structure.

STEP 47B.

(22?, 45) -2-Amino-4- [ (1-methoxy) -2-naphthyl] methyl pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid, mp 168-170 °C. [CC]_D= - 18.7 (c 0.545, Methanol) . ^XH-NMR

(Methanol-d₄) : 7.70 (t, J = 9 .3 Hz, 2H) , 7.60 (s, IH) , 7.32 (dd, J^" = 8.5 and 1.6 Hz, IH) , 7.19 (d, J = 2.4 Hz, IH) , 7.09 (dd, J = 8.9 and 2.4 Hz, IH) , 3.98 (dd, J = 8.5 and 5.6 Hz, IH) , 3.88 (s, 3H) , 3.26-3.14 (m, IH) , 3.09-2.94 (m, 2H) , 2.34 (ddd, J- = 14.9, 9.7 and 5.6 Hz, IH) , 1.94 (ddd, J = 14.5, 8.4 and 4.0 Hz, IH) .

EXAMPLE 48.

(22?, 45) -2-Amino-4- [3- (m-chloro)phenyl-22g-propenyl] pentanedioic acid.

STEP 48A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [3- (m- chloro) phenyl-22?-propenyl] pyroglutamate .

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using m-chloro cinnamyl bromide as reagent. Pale cream solid. NMR data consistent with structure.

STEP 48B. (22?, 45) -2-Amino-4- [3- (m-chloro)phenyl-22?-propenyl] pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid, mp 146-148 ²C. [α]_D= -1.7 (c 0.41, DMSO). ^XH-NMR (D₂0/K0D) : 7.20-6.90 (m, 4H) , 6.22-5.94 (m, 2H) , 2.96 (d, J = 4.3 and 9.2 Hz, IH) , 2.35-2.15 (m, 3H) , 1.70 (m, IH) , 1.32 (m, IH) ¹³C-NMR ( D₂0 /MeOH- d / ROD ) : 184.3, 183.4, 140.0, 134.4, 130. I 130.6, 130.3, 127.4, 126.3, 125.0, 55.3, 46.5, 38.9, 36.8.

EXAMPLE 49.

(22?, 45) -2-Amino-4- [3- (p-phenyl) henyl-2ff-propenyl] pentanedioic acid.

STEP 49A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [3- (p- phenyl) phenyl-2E-propenyl] pyroglutamate .

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using p-phenyl cinnamyl bromide as reagent. Pale cream solid. NMR data consistent with structure.

STEP 49B.

(22?, 45) -2-Amino-4- [3- (p-phenyl) phenyl-2E-propeny1] pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid, mp 192 ²C. [ ]_D = -13.4 (c 0.5, IN NaOH) . ^XH NMR (D₂0/KOD) :

7.55-7.10 (m, 9H) , 6.35-5.94 (m, 2H) , 2.95 (m, IH) , 2.32- 2.00 (m, 3H) , 1.70 (m, IH) , 1.32 ( , IH) . ^X3C NMR (D₂0/MeOH- d₄/KOD) δ 184.0, 183.0, 140.2, 139.2, 137.0, 130.5, 129.2, 127.7, 127.2, 126.8, 54.8, 46.2, 38.4, 36.4.

EXAMPLE 50.

(22?, 45) -2-Amino-4- [ (5-phenyl) -2E, 4E-pentadienyl] pentanedioic acid.

STEP 50A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -4- [ (5- phenyl) -2E, 4E-pentadienyl] pyroglutamate . The title compound was prepared using a similar procedure to that described for Example 1, Step IC, [ (5-phenyl) -2E, AB- pentadienyl] bromide as reagent. Cream solid. NMR data consistent with structure.

STEP 5OB.

(22?, 45) -2-Amino-4- [ (5-phenyl) -225, 42?-pentadienyl] pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid, mp 171-2 ²C. [α]_D= -58 (c 1, IN HCl) . ^αH NMR (D₂0/pyr-d₆) :

7.30-6.90 (m, 5H) , 6.46 (d, J = 10.3 and 15.3 Hz, 1H),6.20 5.95 (m, 2H) , 5.78 (m, IH) , 4.00 (m, IH) , 2.80-1.90 (m, 5H) . ¹³C NMR (D₂0/pyr-d₅) : 184.2, 176.7, 139.2, 135.2, 134.4, 132.4, 131.4, 130.8, 129.5, 128.2, 55.9, 47.4, 38.7, 35.3.

EXAMPLE 51

(22?, 45) -2-Amino-4- (2-propenyl) pentanedioic acid.

STEP 51A. Ethyl (22?, 45) -1- (tert-butoxycarbonyl) -A- ( 2E- propenyl) pyroglutamate .

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using allyl bromide as reagent. White solid. NMR data consistent with structure.

STEP 51B.

(22?, 45) -2-Amino-4- (2-propenyl) pentanedioic acid was prepared following a similar procedure to that described for Example 1, Step ID. White solid, mp 166-7 ²C. [α]_D= -4.5 (c

1, H₂0) . ^XH NMR (MeOH-d₄/D₂0) δ 5.90-5.65 (m, IH) , 5.20-4.90 (m, 2H), 3.70 (m, IH) , 2.70 (m, IH) , 2.55-2.20 (m, 3H) , 1.92 (m, IH) . ¹³C NMR (MeOH-d₄/D₂0) : 181.1, 175.0, 135.9, 118.4, ^■ 54.2, 43.8, 37.4, 33.0. EXAMPLE 52 .

(22?, 45) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid, 1-O-Benzyl ester, hydrochloride salt.

STEP 52A. Benzyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (3- benzo [b] thienyl) methyl pyroglutamate.

The title compound was prepared using a similar procedure to that described for Example 1, Step IC, using Benzyl (22?) -1- ( tert-butoxycarbonyl) pyroglutamate as the starting material and 3- (benzo [b] thienyl) methyl bromide as reagent. ^XH NMR consistent with structure. White solid. 50%.

STEP 52B. (22?, 45) -2-Amino-N- (-tert-butoxycarbonyl) -4- (3- benzo [b] thienyl) methyl pentanedioic acid, 1-O-Benzyl ester. To a solution of Benzyl (22?, 45) -1- (tert-butoxycarbonyl) -4-

(3-benzo [b] thienyl) methyl pyroglutamate (Step 52A, 0.5 mmol) in 12 ml of THF, cooled to 0 °C, was dropwise added a solution of LiOOH (freshly prepared by adding a 0.2 M solution of LiOH, 1.1 equiv, to a mixture of 30% vol H₂0₂, 5 equiv, in 4 ml of water) . The resulting mixture was stirred at 0 °C for 1.5h or until TLC showed complete conversion. The reaction was cooled to -78 °C and a solution of NaHS0₃ (40% vol) in 3 ml of water is added. After the reaction is slowly warmed up to room temperature while stirring vigorously, the mixture is diluted with EtOAc and water, extracted with EtOAc and the organic layer washed with IN HCl, water and brine. Drying over Na₂SU4 and evaporation afforded a crude N-BOC-D-glutamic acid-1-O-ester which was used without further purification. Foamy white solid, 85%. ΝMR data consistent with structure.

STEP 52C.

(22?, 45) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid, 1-O-Benzyl ester, hydrochloride salt, was prepared by stirring the N-BOC precursor with a saturated dry HCl solution in ethyl acetate for one hour at room temperature (10 ml x mmol) . After evaporation, the residue was suspended in Et₂0, filtered off, triturated with ethyl ether (3 x 20 ml) , filtered and dried under high vacuum to afford the hydrochloride salt. Pale yellow solid, 85%%. mp 68-69 °C .

[α]_D= -13.6 (c 0.25, Methanol) . ¹³C NMR (MeOH-d₄) : 177.2, 170.1, 141.9, 139.9, 136.2, 133.8, 129.7, 129.7, 129.3, 125.5, 125.2, 125.0, 124.9, 123.9, 122.7, 122.6, 69.1, 52.7, 42.8, 32.9, 32.1.

EXAMPLE 53.

(22?, 45) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid, 1-O-benzyl, 5-O-ethyl ester, hydrochloride salt.

STEP 53A. (22?, 45) -2-Amino-N- (tert-butoxycarbonyl) -4-.(3- benzo [b] thienyl) methyl pentanedioic acid, 1-O-benzyl, 5-O- ethyl ester . A solution of Benzyl (22?, 45) -1- (tert-butoxycarbonyl) -4- (3- benzo [b] thienyl) methyl pyroglutamate (Step 52A, 0.32 mmol) was dissolved in 8 ml of anhydrous THF and cooled at -78 °C under N₂. In a different flask, lithium ethoxide was prepared at -78 °C under N₂ by adding lithium hexamethyl disilazide (1.0 M soln in THF, 0.8 equiv) to a solution of 0.25 ml of EtOH in 3 ml of THF with stirring. The LiOEt solution was rapidly added via cannula to the pyroglutamate. The mixture was stirred at -78 °C for 1.5h and hydrolyzed by addition of saturated NH₄C1, extracted with Et₂0 and the organic layer washed with water and brine. Drying over MgS0₄ and evaporation in vacuo afforded a crude diester which was purified by silica gel chromatography. Colorless oil, 100%. NMR data consistent with structure.

STEP 53B. (22?, 45) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid, 1-O-benzyl ester, 5-O-ethyl ester, hydrochloride salt, was prepared in a manner analogous to that described in Example 52, Step 52C. White foamy solid. [α]_D= -7.6 (c 0.58, Methanol) . ¹³C NMR (MeOH-d₄) : 175.3, 170.0, 141.8, 139.9, 136.1, 133.7, 129.8, 129.7, 129.7, 125.5, 125.2, 124.9, 123.8, 122.7, 69.3, 62.3, 52.6, 43.2, 33.3, 32.1, 14.2.

EXAMPLE 54. (22?, 42?) -2-Amino-4- (2-benzo [b] thienyl) methyl pentanedioic acid, 1-O-benzyl, 5-O-ethyl ester, hydrochloride salt.

STEP 54A. (22?, 42?) -2-Amino-N- (tert-butoxycarbonyl) -4- (2- benzo [b] thienyl) methyl pentanedioic acid, 1-O-benzyl, 5-0- ethyl ester.

The title compound was prepared in a manner analogous to that described in Example 53, Step 53A, using Benzyl (22?, 42?) -1- (tert-butoxycarbonyl) -4- (2-benzo [b] thienyl) methyl pyroglutamate (prepared as described in Example 1, Step IC from the benzyl pyroglutamate), as the starting material. Yellowish solid, 94%. NMR data consistent with structure.

STEP 54B.

(22?, 42?) -2-Amino-4- (2-benzo [b] thienyl) ethyl pentanedioic acid, 1-O-benzyl ester, 5-O-ethyl ester, hydrochloride salt, was prepared in a manner analogous to that described in Example 52, Step 52C. Pale yellow foamy solid, 92%. mp 55-56

°C. [α]_D= -8.5 (c 2.1, Methanol). ^X3C NMR (CDC1₃) : 173.3, 169.1, 141.0, 139.7, 139.5, 134.3, 128.4, 128.3, 128.2, 128.1, 123.9, 123.5, 122.9, 122.8, 121.9, 68.0, 61.1, 51.9, 42.6, 32.7, 31.8, 13.8.

EXAMPLE 55. (22?, 42?) -2-Amino-4- (2-benzo [b] thienyl) methyl pentanedioic acid, 5-O-ethyl ester, hydrochloride salt.

A solution of (22?, 42?) -2-Amino-4- (2-benzo [b] thienyl)methyl pentanedioic acid, 1-O-benzyl ester, 5-O-ethyl ester, hydrochloride salt (0.2 mmol) was dissolved in MeOH (5 ml), then 4 mol% of 10% Pd/C was added and a hydrogen balloon connected to the reaction flask. After 16h of reaction, the catalyst was filtered through Celite and the solvent evaporated in vacuo. The residue was triturated with Et₂0 to afford the pure aminoacid. Brownish solid, 50%. mp 90-91 °C.

[α]_D= +16.0 (c 0.3, Methanol). ^X3C NMR (Methanol-d₄) : 175.3, 172.4, 142.4, 141.3, 141.0, 125.4, 125.1, 124.2, 124.1, 123.0, 62.5, 50.3, 44.6, 34.0, 33.3, 14.4.

EXAMPLE 56.

(22?, 45) -2-Amino-4- (3-benzo [b] thienyl) methyl pentanedioic acid, 1, 5-di-O-allyl ester.

(22?, 45) -2-Amino-4- (3-benzo [b] thienyl)methyl pentanedioic acid, (Example 6, Step 6B, HCl salt, 0.45 mmol) was dissolved in neat allyl alcohol (4 mL) under N₂ atmosphere and cooled to 0 ²C. SOCl₂ (3 mmol) is added via syringe and the temperature allowed to rise slowly overnight. The solution is concentrated to dryness under vacuum and further dried for 6 hours. Diethyl ether (10 mL) was added to the resulting solid and the slurry filtered. Concentration of the liquor under vacuum afforded the HCl free allyl derivative. 99 % (brownish oil). ^XH-NMR (Methanol-d₄) : 7.82- 7.70 (m, 2H) , 7.40-7.18 (m, 3H) , 5.92-5.55 (m, 2H) , 5.30- 5.00 (m, 4H) ; 4.60-4.35 (m, 4H) , 4.00 (t, J =9.05 Hz, IH) , 3.18-2.95 (m, 3H) , 2.41-2.22 (m, IH) , 2.06-1.88 (m, IH) . ¹³C-NMR (Methanol-d₄) : 174.9, 169.8, 141.9, 139.9, 133.6, 133.1, 132.4, 125.5, 125.2, 125.1, 123.9, 122.6, 119.9, 119.0, 68.1, 66.9, 52.6, 43.2, 33.2, 32.3. EXAMPLE 57 .

(22?, 45) -N'-Phenyl-4- (2-naphthyl) methyl glutamine, hydrochloride salt .

STEP 57A. (22?, 45) -2-Amino-N- (tert-butoxycarbonyl) -4- (2- naphthyl)methyl pentanedioic acid, 1-O-ethyl ester. The title was prepared in a manner analogous to that described in Example 52, Step 52B, from Ethyl (22?,45)-l- (tert-butoxycarbonyl) -4- (2-naphtyl)methyl pyroglutamate (Example 1, Step IC) . 80%. Foamy white solid. NMR consistent with structure.

STEP 57B. (22?, 45) -N- (tert-butoxycarbonyl) -N' -phenyl-4- (2- naphthyl ) methyl glutamine, 1-O-ethyl ester. To a cooled (0 °C) stirred mixture of the starting (22?, 45)- 2-Amino-N- (tert-butoxycarbonyl) -4- (2-naphtyl) methyl pentanedioic acid, 1-O-ethyl ester (1.7 mmol) in 30 ml of THF was added aniline (2.55 mmol), EDCI (ethyl-N,N- diethylaminopropyl carbodiimide, hydrochloride salt, 2.04 mmol), BtOH (1-hydroxybenzotriazole, 2.04 mmol) and finally diisopropyl-ethyl amine (2.55 mmol). The slurry mixture was stirred at 0 °C for 4 h and then for 2 h at rt . Then the mixture^' was evaporated in vacuo and purified by column chromatography (Hex/EtOAc 4:1) to afford a colorless syrup. 76%. NMR data consistent with structure.

STEP 57C.

(22?, 45) -N' -Phenyl-4- (2-naphthyl) methyl glutamine, hydrochloride salt, was prepared by hydrolysis of the ethyl ester with 2.5 N LiOH (see Example 1, Step ID), and then, remove the N-BOC group with dry HCl in a manner analogous to that described in Example 52, Step 52C. White solid, 73%. mp 117-119 °C. ¹³C NMR (Methanol-d₄) mixture of 2 rotamers : 174.4, 171.6, 139.0, 137.0, 134.8, 133.6, 129.6, 129.1, 128.7, 128.5, 128.3, 126.9, 126.5, 125.5, 121.7, 52.5, 46.6, 40.2, 39.3, 33.5, 32.9, 30.7, 24.2.

Claims

WE CLAIM :

A compound of general formula

I in which:

X represents a bond, 0, S, SO or S0₂; and R^x represents a (1-lOC) alkyl, (2-IOC) alkenyl, (2- 10C) alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, or an ester or amide thereof, or a salt thereof, provided that when X represents a bond, R^x cannot represent a 3-phenyl-2- propenyl, 3- (4-chlorophenyl) -2-propenyl, 4-fluorobenzyl or 1-naphthylmethyl group.

2. A compound as claimed in Claim 1, which is a compound of formula I, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof.

3. A compound as claimed in Claim 1 or Claim 2, which has the configuration

la 4. A compound as claimed in any one of Claims 1 to 3 , in which X represents a bond, 0 or S .

5. A compound as claimed in any one of Claims 1 to 4, in which R^x represents a methyl, ethyl, propyl, vinyl, prop-2- enyl, prop-2-ynyl, buta-1, 3-dienyl or carboxamidomethy1 group which is unsubstituted or substituted by (3- IOC) cycloalkyl or an unsubstituted or substituted aromatic group .

6. A compound as claimed in any one of Claims 1 to 5, in which each unsubstituted or substituted aromatic group is selected independently from phenyl, naphthyl, furyl, thienyl, pyridyl, benzofuryl, benzothienyl, benzothiazolyl and indolyl .

7. A compound as claimed in Claim 6, in which each unsubstituted or substituted aromatic group is unsubstituted or substituted by methylenedioxy or by one, two or three substituents selected independently from halogen, (1- 4C) alkyl, (1-4C) alkoxy, (1-4C) alkylthio, halo (1-4C) alkyl, halo (1-4C) alkoxy, cyano, nitro, amino, (1-4C) alkylamino, di (1-4C) alkylamino, carboxy, and a group of formula -(CH₂)_m- X^x-(CH₂)n-R² in which is 0, 1 or 2 , n is 0, 1 or 2 , X¹ represents a bond, 0, S, SO, S0₂, NH, CO, COO, OCO, CONH, NHCO, NHCONH, NHS0₂ or S0₂NH and R² represents an aromatic group which is unsubstituted or substituted by one or two substituents selected independently from halogen, (1-

4C) alkyl, (1-4C) alkoxy, (1-4C) alkylthio, halo (1-4C) alkyl, halo (1-4C) alkoxy, cyano, nitro, amino, (1-4C) alkylamino, di (1-4C) alkylamino or carboxy.

8. A process or the preparation of a compound of formula I, an ester or amide thereof, or a salt thereof, which comprises (A) hydrolysing a compound of formula

II in which R² represents a hydrogen atom or a carboxyl protecting group and R³ represents a hydrogen atom or an amino protecting group; or (B) deprotecting a protected compound of formula

III in which R⁴ and R⁵ each represents a hydrogen atom or a carboxyl protecting group and R⁶ represents a hydrogen atom or an amino protecting group; or an ester or amide thereof; followed, if desired, by

(i) forming an ester or amide; and (ii) forming a salt.

9. A pharmaceutical formulation, which comprises a compound as claimed in any one of Claims 2 to 7, and a pharmaceutically-acceptable carrier, diluent, or excipient.

10. A compound as claimed in any one of Claims 2 to 7 for use as a pharmaceutical .

11. Use of compound of general formula

I in which: X represents a bond, 0, S, SO or S0₂; and

R¹ represents a (1-lOC) alkyl, (2-IOC) alkenyl, (2- 10C) alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for use as a glutamate racemase inhibitor.

12. Use of a compound as defined in Claim 11 for the manufacture of an antibiotic medicament.

13. A method of inhibiting glutamate racemase in a patient requiring such treatment, which comprises administering an effective amount of a compound of formula

I in which: X represents a bond, 0, S, SO or S0₂; and

R¹ represents a (1-1OC) alkyl, (2-10C) alkenyl, (2- 10C) alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-IOC) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof .

14. A method of combating a bacterial infection in an animal in need of treatment, which comprises administering to said animal an effective amount of compound of general formula

I in which:

X represents a bond, 0, S, SO or S0 ; and R^x represents a (1-lOC) alkyl, (2-IOC) alkenyl, (2- IOC) alkynyl, (4-10C) alkadienyl, carboxamido (1-8C) alkyl or aminocarbonyl (1-8C) alkyl group which is unsubstituted or substituted by (3-10C) cycloalkyl or by one or two unsubstituted or substituted aromatic groups, a pharmaceutically acceptable metabolically labile ester or amide thereof, or a pharmaceutically acceptable salt thereof .