WO2000078723A1

WO2000078723A1 - Process for the preparation of butoxycarbonylimino compounds and intermediates therefor

Info

Publication number: WO2000078723A1
Application number: PCT/GB2000/002355
Authority: WO
Inventors: Michael Dennis Dowle; Peter David Howes; John Edward Robinson; Naimish Trivedi
Original assignee: Glaxo Group Ltd
Current assignee: Glaxo Group Ltd
Priority date: 1999-06-19
Filing date: 2000-06-16
Publication date: 2000-12-28
Anticipated expiration: 2001-12-19
Also published as: GB9914306D0; AU5415900A

Abstract

The present invention relates to a novel process for the preparation of butoxycarbonylimino compounds, in particular (tert-butoxycarbonylimino-pyrazol-1-yl-methyl)-carbamic acid tert-butyl ester, otherwise known as bis-boc-1H-pyrazole-1-carboxamidine, or bis-Boc PC, and novel intermediates.

Description

PROCESS FOR THE PREPARATION OF BUTOXYCARBONYLIMLNO COMPOUNDS AND INTERMEDIATES THEREFOR

The present invention relates to a novel process for the preparation of butoxycarbonyiimino compounds, in particular (tert-butoxycarbonylimino- pyrazol-1-yl-methyl)-carbamic acid tert-butyl ester, otherwise known as bis-boc- 1H-pyrazole-1-carboxamidine, or bis-Boc PC, and novel intermediates.

Bis-Boc PC is a valuable reagent for the preparation of bis-Boc protected guanidines from the corresponding amines. It is used as a reagent for the conversion of amines to monosubstituted guanidines and also in the synthesis of arginine containing peptides. In particular, bis-Boc PC can be used in the synthesis of complex guanidine containing compounds for example 5- acetamido-2,3,4,5-tetradeoxy-4-guanidino-D-glycero-D-galactonon-2- enopyranosonic acid (zanamivir) and (1S,2S,3R,4R)-3-[(1R)-1-(acetylamino)-2- ethylbutyl]-4-{[amino(imino)methyl]amino}-2-hydroxycyclopentanecarboxylic acid (BCX-1812).

Bernatowicz et al in Tetrahedron Letters Vol 34, No. 21, pg 3389-3392, 1993, disclose a one step process for the production of bis-Boc PC from the mono-Boc PC.

This preparation is fraught with practical difficulties, because of the large excess of sodium hydride used leading to exothermic reactions, and necessitating the removal of excess quantities of a highly flammable material at the end of the reaction. This preparation is also moisture sensitive. Pasty reaction mixtures are obtained which are at best, difficult to stir. The process can produce yields of up to 80%, dependent on scale, however it is unreliable, as sometimes no bis-Boc PC is obtained, and bis-Boc carbodiimide and pyrazole are major products.

s- oc car o m e pyrazole

We have found a novel method of preparing bis-Boc PC and other Boc-carbonyl pyrazole-1-carboxamidines, which can be used for the bulk preparation of a Boc protected substituted guanidine from the corresponding amine, giving near quantitative yields using catalytic quantities of reagents and avoiding the use of hazardous reagents.

The invention thus provides in the first aspect a process for the preparation of compounds of formula (I):

wherein R represents C^alkyl, aryl, C^alkylaryl, O-C^alkyl, O-aryl, O-C^alkylaryl, an amino acid and protected derivatives thereof;

which comprises the reaction of novel intermediates of formula (lla) or (lib);

wherein R is as defined for compounds of formula (I),

with a metal salt of formula MX_m.nH₂O in solvent, where n can be 0 to 20 and m can be 2 to 5. It will be understood by the person skilled in the art that m is dependent on the valency of the metal.

As used herein, alkyl includes both straight and branched chain saturated hydrocarbon groups optionally substituted with NO₂, CN, CO₂R₆, F, Cl, COR₆, OR₆ or N(R₆)₂, preferably unbranched at the α- position.

Preferably alkyl includes both straight and branched chain saturated hydrocarbon groups optionally substituted with NO₂, CN, CO₂R₆, OCOR₆ F, Cl, COR₆ OH or NH₂, preferably unbranched at the α- position.

As used herein, amino acid means natural and unnatural α-amino acids preferably the natural and unnatural twenty amino acids commonly found in plant and animal proteins and listed on page 961- 962 of Fessenden and Fessenden 4^th Edition.

R₆ can be independently selected from hydrogen C_halky! C_Lgalkylaryl and a protecting group selected from the groups boc, Fmoc, Cbz, and trityl.

Preferably R₆ represents hydrogen, C_halky! and C_1-6alkylaryl.

As used herein, aryl means aromatic carbocyclic and heterocyclic groups. Preferred examples of aryl groups include phenyl, naphthyl, pyridyl, imidazolyl and thienyl. When aryl groups are optionally substituted, suitable substituents include N0₂, CN, CO₂R₆, F, Cl, COR₆, C^alkyl, C^alkoxy, OR₆, trifluoromethyl, N(R₆)₂, phenyl and C^ρalkylaryl. Suitably, substituted aryl groups bear 1 , 2 or 3 substituents.

Preferred substituents are selected from the group NO₂, CN, CO₂R₆, F, Cl, hydroxy, C^alkyl, C^alkoxy, OR₆, trifluoromethyl, amino, phenyl and C^ ₆alkylaryl.

Preferably R represents C^alkyl, aryl, C^alkylaryl, O-C^alkyl, O-aryl, or O-C^alkylaryl, or protected derivatives thereof More preferably R is C^alkyl, phenyl, C,.₆alkylphenyl, O-C^alkyl, O-phenyl, and O-C_Lgalkylphenyl.

Even more preferably R is selected from ethyl, propyl, butyl, tertbutyl, phenyl, ethylphenyl, O-ethyl, O-propyl, O-butyl, O-tertbutyl, O-pentyl, O-hexyl, O- dodecanyl, and O-phenyl.

Preferably M is magnesium or zinc, even more preferably magnesium.

Preferably n is 0 to 6.

Preferably X will be a halide, perchlorate, or triflate anion.

More preferably X will be a perchlorate, or triflate anion.

Even more preferably M is magnesium and n is 0 to 6.

As used herein the term halide means fluoride, chloride, iodide or bromide.

The reaction is conveniently carried out in non reactive solvent preferably tetrahydrofuran or acetonitrile.

The reaction may be carried out at a temperature of 0 to 100 °C under reflux, preferably at a temperature in the range of 0 to 60 °C, even more preferably in the range of 20 to 50 °C, conveniently at the reflux temperature of the chosen solvent.

The molar ratio of metal salt to compound of formula (I) employed in the reaction is preferably from about 0.001 :1 to 0.5:1 , preferably 0.05:1.

The desired boc-carbonyl compound may be isolated by any conventional method from the reaction mixture, for example solvent extraction followed by crystallisation or chromatography. Further aspects of the invention are novel intermediates of formula (Ma) or (Mb).

Specific compounds according to the invention are;

tert-Butoxycarbonyl-(tert-butoxycarbonylimino-pyrazol-1-yl-methyl)-carbamic acid tert-butyl ester; tert-Butyl [{tert-butoxycarbonyl}(2,2-dimethylpropanoyl)amino](1 H-pyrazol-1 ■ yl)methylidenecarbamate;

Butyl tert-butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methylimidodicarbonate; tert-Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methyl(phenylcarbonyl)carbamate; tert-Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1- yl)methyl(phenylethylcarbonyl)carbamate; (Butyl tert-butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methylimidodicarbonate); tert-Butyl phenylmethyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methylimidodicarbonate; bis(tert-Butyl) {[6-({[(9H-fluoren-9-ylmethyl)oxy] carbonyl}amino)hexanoyl]imino}(1 H-pyrazol-1 -yl)methylimidodicarbonate; tert-Butyl 3-({tert-butoxycarbonyl}amino)propanoyl[({tert- butoxycarbonyl}imino)(1 H-pyrazol-1 -yl)methyl]carbamate; bis(tert-Butyl) {[6-({tert-butoxycarbonyl}amino)hexanoyl]imino}(1 H-pyrazol-1 - yl)methylimidodicarbonate; tert-Butyl ethyl ({tert-butoxycarbonyl} imino)(1 H-pyrazol-1 -yl)methylimidodicarbonate;

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl acetate;

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl propanoate;

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2, 8-dioxa-4,6- diazadec-5-en-1-yl benzoate;

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl hexanoate; 4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl dodecanoate; and tert-Butyl 4-({tert-butoxycarbonyl}amino)butyl ({tert-butoxycarbonyl}imino)(1 H- pyrazol-1-yl)methylimidodicarbonate.

A further aspect of the invention is a process for the preparation of compounds of formula (lla) and (Mb) which comprises reacting compounds of formula (III):

wherein R is as defined for compounds of formula (I) with Boc₂O in solvent in the presence of a catalyst.

Compounds of formula (III) are present as tautomers, therefore on reaction with Boc₂O, both compounds of formula (lla) and (Mb) may be obtained. This mixture of compounds of formula (lla) and (Mb) can be reacted without separation giving compounds of formula (I).

The reaction is conveniently carried out in a non-reactive solvent, such as a haloalkane, in particular dichloromethane, or tetrahydrofuran or ethyl acetate.

The reaction is conveniently carried out at ambient temperature, preferably in the range 0 to 30°C preferably 15 to 20 °C.

Preferably the catalyst is 4 -dimethylaminopyridine.

The molar ratio of catalyst to compound of formula (III) or (III) is in the range 0.2:1 to 0.001 :1 , preferably 0.05:1.

The preparation of compounds of formula (lla) and (Mb) from compounds of formula (III) can be carried out in two stages using resin bound bases

(polystyrene resin bases which can be bought from Argonaut Technologies). The procedures which involve simply filtration and evaporation/crystallisation to isolate the product, offer the advantages of convenience and minimal work up.

Compounds of formula (III) are reacted with Boc₂O in the presence of a resin bound base, for example N-(methylpolystyrene)-4-(methylamino)pyridine (resin 4% crosslinked polystyrene-co-divinylbenzene), to form compounds of formula (lla) and (lib).

This reaction can be carried out in the same reaction conditions as the solution phase preparation of compounds of formula (lla) and (Mb) from compounds of formula (III) above.

Compounds of formula (III) can be prepared from pyrazol-1-yl-methyl-carbamic acid hydrochloride (PCH) by reaction with (RCO)₂O, where R is as defined for compounds of formula (I), in the presence of a resin bound base for example polystyrene-DIEA,

N,N-(Diisopropyl)aminomethyipolystyrene (resin 2% crosslinked polystyrene-co- divinylbenzene).

The reaction is conveniently carried out in a non-reactive solvent, preferably dichloromethane.

The reaction may be carried out at a temperature of 0 to 30 °C, preferably in the range of 15 to 30 °C.

The molar ratio of resin bound base to pyrazol-1-yl-methyl-carbamic acid employed in the reaction is preferably from about 1 : 0.5 to 5, more preferably 1 : 1 to 3. Pyrazol-1-yl-methyl-carbamic acid hydrochloride can be purchased from Aldrich.

Compounds of formula (III) wherein R represents O-tertbutyl can be purchased from Aldrich. Bis Boc PC is available from Aldrich, Advanced ChemTech or Chem Impex International. As will be appreciated by those skilled in the art it may be necessary or desirable at any stage in the above described processes to protect the R group in the molecule to prevent undesirable side reactions; the protecting group may be removed at any convenient subsequent stage in the reaction sequence, or after the compound of formula (I) has been used as the reagent for the conversion of an amine to the corresponding guanidine on a compound.

The protecting groups used in the preparation of compounds of formula (I) may be used in conventional manner. See for example 'Protective Groups in Organic Chemistry' Ed. J. F. W. McOmie (Plenum Press 1973) or 'Protective Groups in Organic Synthesis' by Theodora W Greene and P G M Wuts (John Wiley and Sons 1991) Examples of suitable amine protecting groups include acyl type protecting groups e.g. formyl, trifluoroacetyl, acetyl, urethane type protecting groups e.g. benzyloxycarbonyl (Cbz), substituted benzyloxycarbonyl, 9- fluorenylmethoxycarbonyl (Fmoc), f-butoxycarbonyl (Boc), isopropyloxycarbonyl, cyclohexyloxycarbonyl and alkyl type protecting groups e.g. benzyl, trityl, chlorotrityl.

Removal of any protecting groups present may be achieved by conventional procedures.

The following is a list of abbreviations used herein:

Boc is tert-butoxycarbonyl. Boc₂0 is di-tert-butyl dicarbonate.

DMAP is 4-dimethylaminopyridine.

THF is tetrahydrofuran.

DMF is N,N-dimethylformamide.

DIPEA is N,N-Diisopropylethylamine. DCM is Dichloromethane.

PyBOP is Benzotriazole-1-yl-oxy-tris-pyrrolidino-phosphonium hexafluorophosphate; and Rf represents retention factor. The present invention is further described by the following examples which are for illustrative purposes only and should not be construed as a limitation of the invention.

Example 1

(tert-Butoxycarbony limino-pyrazol-1 -yl-methy l)-carbamic acid tert-butyl ester

Intermediate 1

a) Intermediate 1 - tert-Butoxycarbonyl-(tert-butoxycarbonylimino-pyrazol-1-yl- methyl)-carbamic acid tert-butyl ester

Di-tert-butyl dicarbonate (218 g) was added to a stirred mixture of (imino-pyrazol-l-yl-methyl)-carbamic acid tert-butyl ester (105 g) in dichloromethane (500 ml) at 20 °C. After 2 minutes, 4-dimethylaminopyridine catalyst (5.6 g) was added. Carbon dioxide evolution started and built up to approximately 100ml/min over the next 5 minutes. After 2.5 hours gas evolution stopped and more di-tert-butyl dicarbonate (5.3 g) was added to ensure complete reaction. After an additional 30 minutes, the reaction was complete.

The reaction mixture was washed with water (2x500 ml), aqueous acetic acid (3 g acetic acid in 500 ml water), water (500 ml), saturated aqueous sodium hydrogen carbonate (500 ml) and brine (200 ml). The organics were dried

(MgSO₄), filtered and evaporated to give Intermediate 1 as a pale yellow solid (199 g).

Found C, 55.52; H, 7.44; N, 13.69: C₁₉H₃₀N₄O₆ requires C, 55.59; H, 7.37; N, 13.65%

b) (tert-Butoxycarbonylimino-pyrazol-l-yl-methyl)-carbamic acid tert-butyl ester

Magnesium perchlorate hexahydrate (11 g) was added to a stirred suspension of Intermediate 1 (195 g) in tetrahydrofuran (500 ml). The mixture was stirred and warmed gently to around 45 °C when carbon dioxide evolution became vigorous, >100ml/min. The reaction mixture was maintained at around 50 °C for 2 hours and was then cooled and evaporated. The residue was dissolved in dichloromethane (500 ml). The misty solution was filtered. The filtrate was washed with water (2x500 ml), dried (MgSO₄), filtered and evaporated. The resultant oil was dissolved with warming, in cyclohexane (500 ml) during which a solid crystallised from solution. The mixture was cooled and the resultant paste filtered to give the title compound as a very pale yellow solid (118 g).

Found C, 53.94; H, 7.12; N, 17.95:

C₁₄H₂₂N₄O₄ requires C, 54.18; H, 7.15; N, 18.05%

Example 2- an alternative method for preparing Intermediate 1.

tert-Butoxycarbonyl-(tert-butoxycarbonylimino-pyrazol-1-yl- methyl)carbamic acid tert-butyl ester

a) (lmino-pyrazol-1-yl-methyl) carbamic acid tert-butyl ester

Pyrazol-1-ylcarboxamidine hydrochloride (0.44 g) was mixed with N,N- (diisopropyl)aminomethyl polystyrene (resin 2% crosslinked polystyrene-co- divinylbenzene); (1 g 3.68 mmol base/g) in dichloromethane (5 ml). A solution of di-tert-butyl dicarbonate (0.65 g) in dichloromethane (5 ml) was added and the mixture stirred at room temperature for 2 days. The mixture was filtered and the filtrate evaporated in vacuo to give the title compound as a white crystalline solid (0.53 g).

Mass spectrum m/z 111 , 155. b) tert-Butoxycarbonyl-(tert-butoxycarbonylimino-pyrazol-1-yl-methyl)carbamic acid tert-butyl ester (Intermediate 1)

(lmino-pyrazol-1-yl-methyl) carbamic acid tert-butyl ester (0.63 g) was mixed with N-(methylpolystyrene)-4-(methylamino)pyridine (resin 4% crosslinked polystyrene-co-divinylbenzene); (0.5 g 1.47mmol base/g) in dichloromethane (10 ml). A solution of di-tert-butyl dicarbonate (1.3 g) in dichloromethane (10 ml) was added and the mixture stirred at room temperature for 18 hours. The resin was filtered off and the filtrate evaporated in vacuo to give the title compound as a white crystalline solid (1.12 g).

Mass spectrum MH+411

Example 3

A solution of Intermediate 1 (0.1 g) in tetrahydrofuran (2 ml) was added to magnesium bromide hexahydrate (15 mg). The mixture was stirred and heated to around 50 °C under a nitrogen blanket. After 20 hours the reaction was cooled and evaporated. The residue was taken up in dichloromethane and applied to a silica Bond Elut™ cartridge (5 ml). The cartridge was sequentially washed using cyclohexane and dichloromethane as eluent. Combination and evaporation of product bearing fractions gave the title compound as an off-white solid (56 mg) containing a trace of starting material.

Mass spectrum MH⁺ 311.

Example 4

(tert-Butoxycarbony limino-pyrazol-1 -y l-methyl)-carbamic acid tert-butyl ester A solution of Intermediate 1 (0.1 g) in tetrahydrofuran (2 ml) was added to magnesium triflate (16 mg). The mixture was stirred and heated to around 50 °C under a nitrogen blanket. After 4.5 hours the reaction was cooled and evaporated. The residue was taken up in dichloromethane and applied to a silica Bond Elut™ cartridge (5 ml). The cartridge was sequentially washed using cyclohexane and dichloromethane as eluent. Combination and evaporation of product bearing fractions gave the title compound as an off-white solid (75 mg).

Mass spectrum MH+ 311.

Example 5

tert-Butyl [(2,2-dimethylpropanoyl)amino](1 H-pyrazol-1 - yl)methylidenecarbamate

N PVB P

HΓANH₂ HCI Sc ^{C aC}'^d

Intermediate 2 Intermediate 3 Example 5

a) Intermediate 2- N-[imino(1 H-pyrazol-1 -yl)methyl]-2,2-dimethylpropanamide

To a solution of pyrazole-1-carboxamidine hydrochloride (300 mg) in dry DCM (10 ml) was added DIPEA (0.82 ml), PyBOP (1.09 g) and pivalic acid (204 mg). The resulting solution was stirred at room temp overnight. Purification on a Bond Elut™ cartridge gave the compound from cyclohexane/ethyl acetate elutions. Evaporation of the solvent afforded Intermediate 2 as a clear oil (350 mg).

LC/MS: shows a single peak & [MH]⁺ = 195

Similarly prepared were:

N-[lmino(1 H-pyrazol-1-yl)methyl]butanamide as a clear oil, LC/MS: [MH]⁺ = 181 N-[lmino(1 H-pyrazol-1-yl)methyl]benzamide as a white solid LC/MS: [MH]⁺ = 215

N-[lmino(1 H-pyrazol-1 -yl)methyl]-3-phenylpropanamide as a white solid, LC/MS: [MHf = 243

b) Intermediate 3 - tert-Butyl [{tert-butoxycarbonyl}(2,2- dimethylpropanoyl)amino](1 H-pyrazol-1 -yl)methylidenecarbamate

To a solution of Intermediate 2 (0.35 g) in dry DCM (10 ml) was added di-tert- butyl dicarbonate (0.87 g) and DMAP (0.045 g). After stirring at room temperature for 2 hours the mixture was diluted with DCM (30 ml) and washed with water (30 ml), the organic layer was separated, dried over MgSO₄ and evaporated. Bond Elut™ purification afforded the title product from cyclohexane/ethyl acetate (4:1), as a white solid (0.54 g). LC/MS: shows a single peak and [MH]⁺ = 395

Similarly prepared were:

Butyl tert-butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methylimidodicarbonate as a white solid. LC/MS: [MHj⁺ = 381

tert-Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methyl(phenylcarbonyl)carbamate as a white solid. LC/MS: [MH]⁺ = 415

tert-Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methyl(phenylethylcarbonyl)carbamate as a white solid. LC/MS: [MH]⁺ = 443

c) tert-Butyl [(2, 2-dimethylpropanoyl)amino](1 H-pyrazol-1 - yl)methylidenecarbamate

To a solution of Intermediate 3 (0.54 g) in dry THF (10 ml) was added magnesium perchlorate (0.055 g) and the resulting solution was heated at 60 °C. After 2 hours the reaction was cooled to room temperature and Bond Elut™ purification afforded the title compound as a white solid (0.37 g). LC/MS: single peak, [MH]⁺ = 295

H'nmr (CDCI₃,ppm): 9.85(1 H,bs); 8.33(1 H,m); 7.6(1 H,s); 6.45(1 H,m); 1.55(9H,s);

1.3(9H,s)

Similarly prepared were:

tert-Butyl [(propylcarbonyl)amino](1 H-pyrazol-1 -yl)methylidenecarbamate as a white solid LC/MS: [MH]⁺ = 281 H'nmr(CDCI₃,ppm): 9.50(1 H,bs); 8.30(1 H,s); 7.65(2H,bs); 6.45(1 H,m); 2.45(2H,m); 1.75(2H,m); 1.58(9H,s); 1.0(3H,t)

tert-Butyl [(phenylcarbonyl)amino](1 H-pyrazol-1 -yl)methylidenecarbamate as a white solid LC/MS: [MH]⁺ = 315 H'nmr(CDCI_3!ppm): 9.05(1 H,bs); 8.4(1 H,m); 8.08-7.35(6H,m); 6.5(1 H,bs); 1.4(9H,s).

and

as a white solid (a mixture of isomers)

LC/MS: [MH]⁺ = 343 H'nmr(CDCI3,ppm): 9.5(1 H,bs); 8.95(1 H,bs); 8.3(1 H,s); 8.15(1H,s); 7.62(2H,d); 7.5(1H,s); 7.3(5H,m); 6.4(1H,s); 3.1-2.7(4H,m); 1.5(2x9H,s)

Example 6.

Butyl ({tert-butoxycarbony l}imino)(1 H-pyrazol-1 -yl)methy lcarbamate

Intermediate 4 Intermediate 5

Example 6

a) Intermediate 4- (butyl imino(1 H-pyrazol-1 -yl)methylcarbamate)

To a solution of pyrazole-1-carboxamidine hydrochloride (0.3 g) in dry DCM (10 ml) was added triethylamine (0.63 ml) and n-butyl chloroformate (0.29 ml). After 1 hour the reaction was complete and the crude mixture was loaded onto a Bond Elut™ cartridge. The product was obtained from cyclohexane/ether (1 :1). Evaporation of the solvent gave Intermediate 4 as a clear oil (0.42 g).

LC/MS: [MH]⁺ = 211

Similarly prepared was phenylmethyl imino(1 H-pyrazol-1 -yl)methylcarbamate as a white solid. LC/MS: [MH]⁺ = 245

b) Intermediate 5 - (Butyl tert-Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 - yl)methylimidodicarbonate)

To a solution of Intermediate 4 in dry DCM (10 ml) was added di-tert-butyl dicarbonate (0.85 g) and DMAP (0.022 g) and the mixture was stirred at room temperature overnight. The mixture was washed with water (10 ml) and the organic layer was dried over MgS0₄ and purified on a Bond Elut™ cartridge eluting with cyclohexane/ethylacetate (4:1). Evaporation of the solvent afforded Intermediate 5 as a white solid (0.74 g). LC/MS: [MH]⁺ = 411

Similarly prepared was tert-butyl phenylmethyl ({tert-butoxycarbonyl}imino)(1 H- pyrazol-1-yl)methylimidodicarbonate as a white solid . LC/MS: [MH]⁺ = 445 c) Butyl ({tert-butoxycarbonyl}imino)(1 H-pyrazol-1 -yl)methylcarbamate

To a solution of Intermediate 5 (0.74 g) in dry THF (10 ml) was added magnesium perchlorate (0.080 g) and the resulting solution was heated at 60 °C. After 2 hours the reaction was cooled to room temp and Bond Elut™ purification afforded the title compound as a white solid (0.52 g).

LC/MS: single peak, [MH]⁺ = 311 H'nmr(CDCI₃,ppm): 9.0(1H,s); 8.30(1H,m); 7.65(1H,s); 6.45(1H,m); 4.20(2H,t); 1.7(2H,m); 1.5(9H,s); 1.45(2H,m); 0.95(3H,t).

Similarly prepared was tert-butyl ({[(phenylmethyl)oxy]carbonyl}amino)(1 H- pyrazol-1-yl)methylidenecarbamate as a white solid. LC/MS: single peak, [MH]⁺ = 344

H'nmr(CDCI3,ppm): 9.05(1 H,s); 8.3(1 H,s); 7.65(1 H,s); 7.5-7.3(5H,m); 6.45(1 H,s); 5.2(2H,m); 1.5(9H,s).

Example 7

9H-Fluoren-9-ylmethyl {[6-({tert-butoxycarbonyl}amino) hexanoy l]amino}(1 H-pyrazol-1 -y l)methy lidenecarbamate.

Intermediate 6 Intermediate 7

Example 7 a) Intermediate 6- 9H-fluoren-9-ylmethyl 6-{[imino(1 H-pyrazol-1- yl)methyl]amino}-6-oxohexylcarbamate

N-(9-Fluorenylmethoxycarbonyl)-6-aminohexanoic acid (2.4 g) was added to a stirred mixture of PyBOP (4.3 g) and diisopropylethylamine (1.98 g) in dichloromethane (50 ml) at 20 °C. After 12 hours the mixture was washed with water (50ml). The organics were dried (MgSO₄) filtered and evaporated. The resultant oil was purified by silica column to give Intermediate 6 as a white solid (3.0g). TLC: 1 :1 ethyl acetate/cyclohexane Rf 0.26. LC/MS: MH+ 446

Similarly prepared were:

tert-Butyl -6-{[imino(1 H-pyrazol-1 -yl)methyl]amino}-6-oxohexylcarbamate as a colourless oil. TLC: 1 :1 ethyl acetate/cyclohexane Rf 0.26

LC/MS: MH+446

tert-Butyl -6-{[imino(1 H-pyrazol-1 -yl)methyl]amino}-3-oxopropylcarbamate as a colourless oil. TLC: 7:3 cyclohexane/ethyl acetate Rf 0.1 LC/MS: MH+283

tert-Butyl (2S)-2-({tert-butoxycarbonyl}amino)-4-{[imino(1 H-pyrazol-1 - yl)methyl]amino}-4-oxobutanoate as a white solid, LC/MS MH+ 382

tert-Butyl (2S)-2-({tert-butoxycarbonyl}amino)-4-{[imino(1 H-pyrazol-1 - yl)methyl]amino}-5-oxopentanoate as a white solid, LC/MS MH+ 396.

tert-Butyl-(2S)-2-[(tert-butoxycarbonyl)amino]-5-{[imino(1 H-pyrazol-1- yl)methyl]amino}-5-oxopentanoate as a white solid, LC/MS MH+ 396.

tert-Butyl -(2S)-2-({tert-butoxycarbonyl}amino)-4-{[imino(1 H-pyrazol-1 - yl)methyl]amino}-4-oxobutanoate as a white solid, LC/MS MH+ 382.

b) Intermediate 7 bis(tert-butyl) {[6-({[(9H-fluoren-9-ylmethyl)oxy] carbonyl}amino)hexanoyl]imino}(1 H-pyrazol-1-yl)methylimidodicarbonate Di-tert-butyl dicarbonate (1.96 g) was added to a stirred solution of intermediate 6 (2.0 g) in dichloromethane (50 ml) at 20 °C. After 2 minutes, 4-dimethylamino pyridine catalyst (100 mg) added. The mixture was stirred for 1 hour, then washed with water (50 ml). The organics were dried (MgSO₄), filtered and evaporated. The resultant oil was purified by silica gel column chromatography to give the Intermediate 7 as a colourless oil (2.58 g). TLC: 1 :1 ethyl acetate/cyclohexane Rf 0.47 LC/MS: MH+ 646

Similarly prepared were:

tert-Butyl 3-({tert-butoxycarbonyl}amino)propanoyl[({tert- butoxycarbonyl}imino)(1 H-pyrazol-1 -yl)methyl]carbamate as a colourless oil. TLC: 1 :1 hexane/ethyl acetate Rf 0.30 LC/MS: MH+483.

bis (tert-Butyl ){[6-({tert-butoxycarbonyl}amino)hexanoyl]imino}(1 H-pyrazol-1 - yl)methylimidodicarbonate as a colourless oil, TLC: 1:1 cyclohexane/ethyl acetate Rf 0.46 LC/MS MH+ 524

tert-Butyl -(2S)-2-[(tert-butoxycarbonyl)amino]-5-{(tert-butoxycarbonyl)[[(tert- butoxycarbonyl)imino](1 H-pyrazol-1 -yl)methyl]amino}-5-oxopentanoate as a white solid, LC/MS MH+ 596.

tert-Butyl -(2S)-2-[(tert-butoxycarbonyl)amino]-4-{(tert-butoxycarbonyl)[[(tert- butoxycarbonyl)imino](1 H-pyrazol-1 -yl)methyl]amino}-4-oxobutanoate as a white solid, LC/MS MH+ 582.

c) 9H-fluoren-9-ylmethyl {[6-({tert-butoxycarbonyl} amino)hexanoyl]amino}(1 H-pyrazol-1 -yl)methylidenecarbamate

Magnesium perchlorate (86 mg) was added to a stirred solution of Intermediate 7 (2.5 g) in tetrahydrofuran (20 ml). The mixture was stirred and warmed to 50 °C for 3 hours, cooled and evaporated. The residue was dissolved in ethyl acetate (50 ml) and washed with water (50 ml), dried (MgSO₄), filtered and evaporated. The resultant oil was purified by silica column to give the title compound as a colourless oil (2.0 g). TLC: 1 :1 ethyl acetate/cyclohexane Rf 0.22

LC/MS: MH+ 546

Similarly prepared were the amides of:

tert-Butyl {[3-({tert-butoxycarbonyl}amino)propanoyl]amino}(1 H-pyrazol-1 - yl)methylidenecarbamate as a colourless oil. TLC: 1 : 1 ethyl acetate Rf 0.5 LC/MS MH+ 382

tert-Butyl-(2S)-2-[(tert-butoxycarbonyl)amino]-5-{[[(tert- butoxycarbonyl)imino](1 H-pyrazol-1 -yl)methyl]amino}-5-oxopentanoate as a white solid, LC/MS MH+ 496.

tert-Butyl-(2S)-2-[(tert-butoxycarbonyl)amino]-4-{[[(tert- butoxycarbonyl)imino](1 H-pyrazol-1 -yl)methyl]amino}-4-oxobutanoate as a white solid, LC/MS MH+ 482.

Example 8

Tert-butyl {[(ethy loxy)carbony l]amino}(1 H-pyrazol-1 - yl)methylidenecarbamate

Intermediate 8 Example 8

a) Intermediate 8 - tert-butyl ethyl ({tert-butoxycarbonyl} imino)(1 H-pyrazol-1 -yl)methylimidodicarbonate. A solution of (tert-butoxycarbonylimino-pyrazol-l-yl-methyl)-carbamic acid tert- butyl ester (1.55 g) in dichloromethane (25 ml) was treated with ethyl chloroformate (1.085 g), di-isopropylethylamine(1 ml) and DMAP(50 mg). The resulting solution was kept at 22 °C for 17 hours. The mixture was purified by chromatography on a Bond Elut™ cartridge (silica, 20 g) eluting with cyclohexane/dichloromethane mixtures, affording the title product as a white solid (1.67 g). m/z (M + H⁺) 383.

Similarly were prepared

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl acetate as a pale yellow gum. m/z (M + H⁺) 427.

4-{[tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa- 4,6-diazadec-5-en-1-yl propanoate as a pale brown oil. m/z (M + H⁺) 441.

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1 H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl benzoate as a white foam, m/z (M + H⁺) 489.

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl hexanoate as a white foam, m/z (M + H⁺) 483.

4-{tert-Butoxycarbonyl}-9,9-dimethyl-3,7-dioxo-5-(1H-pyrazol-1-yl)-2,8-dioxa-4,6- diazadec-5-en-1-yl dodecanoate as a white foam, m/z (M + H⁺) 567.

tert-Butyl 4-({tert-butoxycarbonyl}amino)butyl ({tert-butoxycarbonyl}imino)(1 H- pyrazol-1-yl)methylimidodicarbonate as a colourless oil. m/z (M + H⁺) 526.

b) tert-butyl {[(ethyloxy)carbonyl]amino}(1 H-pyrazol-1 -yl)methylidenecarbamate

A solution of Intermediate 8 (382 mg) in THF (5 ml) was treated with magnesium perchlorate (40 mg) at 60 °C for 2 hours. The reaction mixture was loaded onto a Bond Elut™ cartridge (silica, 20 g) and eluted successively with cyclohexane, dichloromethane and ethyl acetate to give the title product as a colourless oil (279 mg). m/z (M + H⁺) 283. ¹H NMR (400MHz, CDCI₃) δ 9.03 br, 1 H), 8.32 (d, 1 H), 7.67 (d, 1 H), 6.46 (dd, 1 H), 4.27 (q, 2H), 1.53 (s, 9H),1.37 (t, 3H).

Similarly were prepared

9,9-Dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa-4,6-diazadec-5-en-1 -yl acetate as a colourless gum. m/z (M + H⁺) 327. ¹H NMR (400MHz, CDCI₃) δ 9.13 ( br, 1 H), 8.30 (d, 1 H), 7.68 (br, 1 H), 6.48 (dd, 1 H), 5.84 (s, 2H), 2.16 (s, 3H), 1.53 (s, 9H).

9,9-Dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa-4,6-diazadec-5-en-1-yl propanoate as a pale brown gum. m/z (M + H⁺) 341. ¹H NMR (400MHz, CDCI₃) δ 9.02 (br, 1 H), 8.30 (d, 1 H), 7.69 (br, 1H), 6.47 (dd, 1 H), 5.86 (s, 2H), 2.44 (q, 2H), 1.53 (s, 9H), 1.18 (t, 3H).

9,9-Dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa-4,6-diazadec-5-en-1-yl benzoate as a white foam, m/z (M + H⁺) 389. ¹H NMR (400MHz, CDCI₃) δ 9.12 ( br, 1 H), 8.30 (d, 1 H), 8.15 (d, 2H), 7.67 (d, 1H), 7.58 (t, 1 H), 7.44 (t, 2H), 6.47 (dd, 1 H), 6.11 (s, 2H), 1.58 (s, 9H).

9,9-Dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa-4,6-diazadec-5-en-1-yl hexanoate as a white solid, m/z (M + H⁺) 383. ¹H NMR (400MHz, CDCI₃) δ 9.12 (br, 1H), 8.30 (d, 1 H), 7.68 (d, 1 H), 6.48 (dd, 1 H), 5.85 (s, 2H), 2.41 (t, 2H), 1.67 (2H), 1.53 (s, 9H), 0.90 (t, 3H).

9, 9-Dimethyl-3,7-dioxo-5-(1 H-pyrazol-1 -yl)-2,8-dioxa-4,6-diazadec-5-en-1-yl dodecanoate as a white solid, m/z (M + H⁺) 467. ¹H NMR (400MHz, CDCI₃) δ 9.12 (br, 1 H), 8.30 (d, 1 H), 7.68 (d, 1 H), 6.47 (dd, 1 H), 5.85 (s, 2H), 2.40 (t, 2H), 1.66 (m, 2H), 1.52 (s, 9H) 1.2-1.35 (m, 16H), 0.88 (t, 3H).

1 , 1 -Dimethylethyl 12,12-dimethyl-6, 10-dioxo-8-(1 H-pyrazol-1 -yl)-5, 11 -dioxa-7,9- diazatridec-8-en-1-ylcarbamate as a white foam, m/z (M + H⁺) 426. ¹H NMR (400MHz, CDCI₃) δ 9.03 (br, 1H), 8.31 (d, 1H), 7.668 (d, 1H), 6.46 (dd, 1H), 4.58 (br, 1 H), 4.22 (t, 2H), 3.18 (br, 2H), 1.76 (m, 2H), 1.63 (m, 2H), 1.51 (s, 9H), 1.43 (s, 9H).

Claims

1. A process for the preparation of a compound of formula (I):

wherein R represents C^alkyl, aryl, C^alkylaryl, O-C.,.₁₂alkyl, O-aryl, O-C^alkylaryl, an amino acid and protected derivatives thereof;

which comprises, the reaction of an intermediate of formula (lla) or (Mb);

wherein R is as defined for a compound of formula (I);

with a metal salt of formula MX_m.nH₂O in solvent, where n can be 0 to 20 and m can be 2 to 5.

2. A process as claimed in claim 1 wherein M is magnesium or zinc.

3. A process as claimed in claim 1 or claim 2 wherein X represents a halide, perchlorate, or triflate anion.

4. A process as claimed in any preceding claim wherein the solvent is a non reactive solvent.

5. A process as claimed in any preceding claim wherein the temperature is in the range 0 to 100 °C.

6. A process as claimed in any preceding claim wherein the molar ratio of metal salt to compound of formula (I) is in the range 0.001 :1 to 0.5:1.

7. A compound of formula (lla) or (lib):

wherein R is as defined in claim 1.

8. A process for the production of a compound of formula (lla) or (Mb) which comprises reacting a compound of formula (III):

with Boc₂O, in solvent in the presence of a catalyst.

9. A process as claimed in claim 8 wherein the solvent is a non-reactive solvent.

10. A process as claimed in any of claims 8 to 9 wherein the temperature of the process is in the range 0 to 30 °C.

11. A process as claimed in any of claims 8 to 10 wherein the molar ratio of the catalyst to compound of formula (lla) or (Mb) is in the range 0.2 :1 to 0.001 :1.

12. Use of a compound of formula (I) as prepared by a process as claimed in any one of claims 1 to 6 to effect the conversion of an amine containing compound to a guanidine containing compound.

13. Use as claimed in claim 12 wherein the guanidine containing compound is zanamivir or BCX-1812.