IL142568A - Method for the preparation of fluticasone and related 17??-carbothioic esters using a novel carbothioic acid synthesis and novel purification methods - Google Patents

Description

iiiniuiniiiiiiiiiiiii 142568 f7'n | 453364 τηκ fiwit) nir ? _n fc ρ>ΐ >τι¼ιρ Τ\ΧΜΡ> mro ^ METHOD FOR THE PREPARATION OF FLUTICASONE AND RELATED 17p-CARBOTHIOIC ESTERS USING A NOVEL CARBOTHIOIC ACID SYNTHESIS AND NOVEL PURIFICATION METHODS METHOD FOR THE PREPARATION OF FLUTICASONE AND RELATED 17S-CARBOTHIOIC ESTERS USING A NOVEL CARBOTHIOIC ACID SYNTHESIS AND NOVEL PURIFICATION METHODS Technical Field This invention relates to a novel method for the conversion of carboxylic acids to carbothioic acids, use of the method for the preparation of androstane 17p-carbothioic acids, and methods for the preparation of fluticasone propionate.

Background of the Invention . ' Fluticasone propionate belongs ; to a class jof androstane 17 -carbothioic esters which are well-known in the art as antiinflammatories. Because of the therapeutic usefulness of these compounds, there is sustained interest in improving the synthesis of androstane 17p-carbothioic esters in general, and fluticasone propionate in particular.

Prior art such as United States patents 4,188,385, 4,198,403, 4,335,121 , and 4,578,221 ; British patents 2,088,877 and 2,137,206; and published Israeli patent application IL 109,656-A1 teach the synthesis of fluticasone propionate from commercial grade flumethasone. These syntheses involve complicating factors such as chromatography of intermediates, low-yielding steps, and high pressure addition of chlorofluoromethane.

Commercial grade flumethasone ((6a, 1 1 β, 16a)-6,9-difluoro- 1 1 ,17,21 -trihydroxy- 16- methylpregna-l,4-diene-3 ,20-dione) typically contains from about 0.5% to 2% of (6a, 1 1 β, 16a)-6-chloro-9-fluoro- 11 , 17,21 -trihydroxy- 16-methylpregna- 1 ,4-diene-3 ,20-dione as an impurity (hereinafter referred to as the CI impurity), the removal of which is achieved -20 — by eolumn-ehromatographyra method not amenable to large scale manufacture.

Conversion of the 17p-carboxylic acid of 6a,9a-difluoro-l 1 p-hydroxy-16a-methyl-3- oxo-17a-(propionyloxy)androsta-l ,4-diene-l 7p-carboxylic acid to a carbothioic acid is also — problematic. -General methods for the conversion of carboxylic acids to carbothioic acids include reaction of activated carboxylic acids and a sulfide source (Advanced Organic Chemistry. Reactions, Mechanisms, and Structure, 4th ed., John Wiley & Sons, New York, 1992; and United States patent 4,578,221) and applieation-of-thioearbamate hydrolysis ; " chemistry to thiocarbamylanhydrides (Bull. Chem. Soc. Jpn., 1977, 50(1 ί), 3071 ; J. Ind. - -- » Chem. Soc, 1977, 52, 150; J. Org. Chem., 1966, 31, 3980; Org. Syn., 1988, Collective Volume VI, 824; J. Am. Chem. Soc. 1947, 69, 2682; and ynlett., 1996, Π , 1054). Use of these methods in the synthesis of fluticasone propionate, however, provide^ ~~ 142568/2 only modest yields due to incompatibility of the reaction conditions with other groups on the molecule (J. Med. Chem., 1984, 37(22) 3171 and J. Org. Chem. 1986, 51(12) 2315).

Direct conversion of the carbothioic acid group of androstane 17p-carbothioic acids to a carbothiolate esters is achieved by reaction of the carbothioic acids, chlorofluoromethane, and base at high pressures, another method which is not amenable to large scale manufacture.

Thus, there is a continuing need in the pharmaceutical manufacturing industry for an efficient method for the conversion of carboxylic acids to carbothioic acid esters which is applicable to the large scale conversion of androstane 17p-carboxylic acids to androstane 17p-carbothioic esters in general and fluticasone propionate, in particular.

Summary of the Invention The present invention provides a method for the preparation of a compound of formula (7) wherein the symbol -represents a single bond or a double bond; one of R1 or R2 is hydrogen and the other is optionally protected hydroxyl; or R1 and R2 together are oxo; R3 and R4 are independently hydrogen or halide; and R5 and R6 are independently Ci-C6 alkyl; the method comprising: (c) reacting a compound of formula (3) and a first base, an iodide salt, and the compound of formula (4) 142568/1 wherein R7 and R8 are independently Ci-C6 alkyl; or R7 and R8 together are Ci-C6 alkylene, in a solvent comprising 2-butanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3) to provide a compound of formula (5) (d) reacting the product of step (c) and NaSH to provide a compound of formula (6) (e) reacting the product of step (d) and acid; (f) reacting the product of step (e) and chlorofluoromethane optionally in the presence of a second base; and (g) optionally deprotecting the product of step (f). - 2a - In one embodiment of this invention is disclosed a method for converting carboxylic acid groups to carbothioic acid groups comprising; (a) reacting a compound having the carboxylic group and a first base, an iodide salt, and a compound of formula (4) wherein R7 and R8 are independently CrC6 alkyl; or R7 and R8 together are C|-C6 alkylene; (b) reacting the product of step (a) and a hydrolyzing agent; and (c) reacting the product from step (b) and acid.

In a preferred embodiment of the above method directly above is disclosed a method for the conversion of a carboxylic acid group to a carbothioic acid group, the method comprising: (a) reacting a compound having the carboxylic acid group and a first base, an iodide salt, and N,N-dimethylthiocarbamoyl chloride at about 10 °C to about 30 °C in a solvent system comprising an organic component and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound having the carboxylic acid group; (b) reacting the product from step (a) and an alkoxide salt, a thioalkoxide salt, an optionally hydrated sulfide salt, or a mixture thereof at about -40 °C to about 35 °C; and (c) reacting the product from step (b) and acid.

In another embodiment of this invention is disclosed a method for dehalogenating a 4-halo-2,3-unsaturated carbonyl group comprising reacting a compound having the 4-halo-2,3- - 2b - unsaturated carbonyl group, a palladium catalyst, and an additive, optionally in the presence of a reducing agent.

In another embodiment of this invention is disclosed a method for the preparation of compound of formula (7) wherein the symbol — represents a single bond or a double bond; one of R' or is hydrogen and the other is optionally protected hydroxyl; or R and R together are oxo and R4 are independently hydrogen or halide; and R5 and R6 are independently C,-C6 alkyl; the method comprising: (b) reacting the product of step (a) and an alkanoyl halide and the firs base to~provide~a~ (d) reacting the product of step (c) and a hydrolyzing agent to provide a compound of formula (f) reacting the product of step (e) and chlorofluoromethane optionally in the presence of a second base; and ' * (g) optionally deprotecting the product of step (f).

In a preferred embodiment of the method directly above, the compound of formula (1) is commercial grade flumethasone; the compound of formula (2) is 6oc,9a-difluoro-l 1 β,17a-dihydroxy-l 6a-methyl-3- oxoandrosta- 1 ,4-diene- 17 -carboxylic acid; : the compound of formula (3) is 6a,9a-difluoro- ί ϊ -hydroxy-16a-rneIhyT-3-oxo-17 - (propionyloxy)androsta- 1 ,4-diene- 17p-carboxylic acid; the compound of formula (5) is 17 -(N,N-(dimethylcarbamoyl)thio)carbonyl-6 ,9a- difluoro- 11 β-hydroxy- 16a-methyl- 17a-propionyloxy-3 -oxoandrosta- 1 ,4-diene;- and the compound of formula (7) is 6 ,9a-difluoro-17a-(((fluoromethyl)sulfanyl)- carbonyl)- β-hydroxy- 16a-methyl-3-oxoandrosta- 1 ,4-dien- 17a-yl propionate.

In another embodiment of this invention is disclosed a method for the purification of -. 6a,9a-difluoro-l 1 -hydroxy-16a-methyl-3-oxo-17a-(propionyloxy)androsta-l ,4-diene-17β- carboxylic acid by recrystallization. ~ In another embodiment of this invention is disclosed a method for the purification of 6a,9a-difluoro-l 1 β-hydroxy-l 6a-methyl-3-oxo-17 -(propionyloxy)androsta-l ,4-diene-l 7β- carboxylic acid by repeated recrystallization.

In another embodiment of this invention is disclosed a method for the purification of 5 the compound formula (1), the compound of formula (2), the compound of formula (3), the compound of formula (5), or the compound of formula (7) by treatment with a palladium catalyst and an additive, optionally in the presence of a reducing agent.

In another embodiment of this invention is disclosed an improved method for the preparation of 6a,9a-difluoro-17 -(((fluoromethyl)sulfanyl)carbonyl)-l 1 -hydroxy-16a-10 methyl-3-oxoandrosta-l ,4-dien-17cc-yl propionate (fluticasone propionate) which omits the use of column chromatography and is applicable to large scale.

In another embodiment of this invention is_disclosed a method for the removal of the CI impurity in the synthesis of fluticasone propionate using a palladium catalyst and an additive, optionally in the presence of a reducing agent.

In another embodiment of this invention is disclosed a method for the removal of the CI impurity from commercial grade flumethasone using a palladium catalyst and an additive, optionally in the presence of a reducing agent .

Detailed Description of the Invention This invention discloses a novel method for the conversion of carboxylic acids to carbothioic acids and application of the method to the preparation of androstane carbothiolates, such as fluticasone propionate, which avoids column chromatography.

Definition of Terms '25 — — The term "acid," as used herein, refers to reagents capable of donating protons during the course of a chemical reaction. Examples of acids include mineral acids such as hydrofluoric, hydrochloric, hydrobromic, hydroiodic, sulfuric, phosphoric, and the like; — . — organic acids such as formic, acetic, propionic, trifluoroacetic, and the like; and sulfonic acids such as para-toluenesulfonic, para-bromosulfonic, para-nitrosulfonic, and the like. The acid 30 chosen for a particular conversion depends orfthe nature of the starting materials, the solvent or solvents in which the reaction is conducted^and the temperature at which the reaction is ... conducted. — The term "additive," as used herein, refers to monodentate phosphorus-containing ligands of formulas P(R )3 (phosphiries) and P(OR )3 (phosphites), wherein each R is independently hydrogen; C)-C6 alkyl such as "cyclopropyl and cyclohexyl; optionally substituted aryl such as phenyl, naphthyl, and ortho- . . tolyl; and optionally substitted heteroaryl such as furyl and pyridyl; and wherein each R is independently C C6 alkyl such as methyl, ethyl, and tert-butyl; cycloalkyl such as cyclopropyl and cyclohexyl; optionally substituted aryl such as phenyl, naphthyl, and ortho- . tolyl; and optionally substituted heteroaryl such as furyl and pyridyl. Specific examples of 5 these additives include tri(alkyl)phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, and the like; tri(cycloalkyl)phosphines such as tricyclopropylphosphine, tricyclohexylphosphine, and the like; tri(aryl)phosphines such as triphenylphosphine, trinaphthylphosphine, and the like; tri(heteroaryl)phosphines such as tri(fury-2-yl)phosphine, tri(pyrid-3-yl)phosphine, and the like; tri(alkyl)phosphites such as trimethylphosphite, triethylphosphite, tributylphosphite, and the like; tri(cycloalkyl)-phosphites such as tricyclopropylphosphite, tricyclohexylphosphite, and the like; tri(aryl)phosphites such as triphenylphosphite, trinaphthylphosphite, and the like; and tri(heteroaryl)phosphites.such_as tri(fury-2-yl)phosphite, tri(pyrid-3-yl)phosphite, and the like. The term "additive," as used herein, also refers to bidentate phosphines such as l,4-bis(diphenylphosphino)butane (dppb), l,2-bis(diphenyl-phosphino)ethane (dppe), l,l-bis(diphenylphosphino)methane (dppm), l,2-bis(dimethyl-phosphino)ethane (dmpe), 1 ,1'- bis(diphenylphosphin0)ferrocene (dppf), and the like.

The term "alkali metal iodide," as used herein, refers to lithium iodide, sodium iodide, potassium iodide, cesium iodide, and the like.

The term "alkali earth metal iodides," as used herein, refers to magnesium iodide, calcium iodide, barium iodide, and the like.

The term "alkanoyl halide," as used herein, refers to RAC(0)X, wherein RA is Cj-C6 alkyl, and X is chloride or bromide. i-Jrhe-term_lC2 C6 alkenyl," as used herein, refers to a straight or branched chain "25 hydrocarbon radical having from 2~to 6~carbons and at : least one carbon-carbon double bond.

The term "alkoxide salt," as used herein, refers to [M]+[ORA] , wherein M is Li, Na, or K, and RA is CrC6 alkyl. — 1 — - The term "alkoxy," as-used -herein, -refers to an alkyl group attached to the parent molecular group through an oxygen atom. .

The terms "C]-C6 alkyl," as used herein, refers to a straight or branched chain saturated hydrocarbon radical having from 1 to 6 carbons. — — — - . - The-term "C Cft alkylene," as used herein, refers to a straight or branched chain saturated hydrocarbon diradical having from 1 to 6 carbons.

The term "amino," as used herein, refers to -NH2 or a derivative thereof formed by ' 35 replacement of a hydrogen atom thereon or independent replacement of both hydrogen atoms " " ^tffereorfby^an alkyl, cycloalkyl, cycloalkylalkyl, or arylalkyl group. ·- The term "aryl," as used herein, refers to a cyclic, aromatic carbocyclic ring such as phenyl or two fused aromatic carbocyclic rings such as naphthyl. The aryl groups of this invention can be optionally independently substituted with one, two, or three alkyl, amino, halo, and nitro substituents. The aryl groups of this invention can bejaptionally independently substituted with one, two, three, four, or five CrC6 alkyl, C2-C6 alkenyl, halo, carboxyl, carboxaldehyde, alkoxycarbonyl, C]-C6 perfluoroalkyl, or nitro substituents.

The term "arylalkyl," as used herein refers to an aryl group attached to the parent molecular group through an alkyl group.

The term "borane," as used herein, refers to compounds containing' at least one boron-hydrogen bond and are exemplified by diborane, 9-borabicyclo[3,3.1]nonane (9-BBN), dilongifoylborane, thexylbprane, catecholborane, sodium borohydride, tetrabutylammonium borohydride, borane-4-methylmorpholine complex, borane-4-ethylmorpholine complex, borane-dimethylsulfide complex, borane-triethylamine complex, borane-pyridine complex, borane-2,6-lutidine complex, and the like.

The term "carbonate salt," as used herein, refers to lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, and the like.

The term "carbothioic acid," as used herein, refers to -C(0)SH.

The terms "carboxylic acid" and "carboxyl," as used herein, refer to -C(0)OH.

The term "carboxaldehyde," as used herein, refers to -CHO.

The term "commercial grade flumethasone," as used herein, refers to (6a, 1 1 β,16α)-6,9-difluoro-l l ,17,21-trihydroxy-16-methylpregna-l,4-diene-3,20-dione containing up to 2% of (6a,l i ,16a)-6-chloro-9-fluoro-l l,17,21-trihydroxy-16-methylpregna-l ,4-diene-3,20-dione as an impurity.

The term "cycldalkyl," as used herein refers to a- saturated, cyclic hydrocarbon group-having three to six carbon atoms.

, . The term "cycloalkylalkyl," as used herein refers to a cycloalkyl group attached to the parent molecular group -through an alky l-group. — - — The term "dehalogenating," as used herein, 'refers to The removal~of a~chloride bromide, or iodide radical of a 4-halo-2,3-unsaturated carbonyl group.

The terms "first base," and "second base," as used herein, refer to reagents capable of accepting protons during the course of a chemical reaction. Examples of first and second . _ bases include carbonates such as lithium carbonate, lithium bicarbonate, sodium carbonate, sodiunrbicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, and the like; phosphates such as potassium phosphate7potassium hydrogen phosphate, potassium dihydrogen phosphate, and the like; trialkylamines^sucli as triethylamine, """ """"" diisopropylethylamine, and the like; heterocyclic amines such as imidazole, pyridine, pyridazine, pyrimidine, pyrazine, and the like; and bicyclic amines such as DBN, DBU, and the like. The base chosen for a particular conversion depends on the nature of the starting materials, the solvent or solvents in which the reaction is conducted, and the temperature at 5 which the reaction is conducted.

The terms "halide" and "halo," as used herein, refer to F, CI, Br, and I.

The term "4-halo-2,3-unsaturated carbonyl," as used herein, refers to a endogenous or exogenous group comprising at least four carbon atoms, wherein carbon- 1 is substituted with oxo, carbon-2 and carbon-3 are connected by a carbon-carbon double bond, and carbon-4 10 bears a chloride, bromide, or iodide substituent.

The term "heteroaryl," as used herein, refers to aromatic rings having five or six atoms, wherein at least one of the atoms is nitrogen, oxygen, or sulfur and the remainder are carbon. The five-membered rings have two double bonds, and the six-membered rings have three double bonds. The heteroaryls of this invention are connected to the phosphorus atom 15 through a carbon atom in the ring. The heteroaryl groups of this invention can be optionally independently substituted with one, two, or three C[-C6 alkyl, C2-C6 alkenyl, halo, carboxyl, carboxaldehyde, alkoxycarbonyl, CrC6 perfluoroalkyl, or nitro substituents.

The term "hydroxy!," as used herein, refers to -OH.

The term "hydroxyl protecting group," as~used herein, refers to selectively introducible and removable groups which protect hydroxyl groups against undesirable side reactions during synthetic procedures. Examples of hydroxyl protecting groups include benzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, 4-bromobenzyloxycarbonyl, 4- methoxybenzylpxycarbonyl, 3,4-dimethoxybenzyloxycarbonyl, methoxycarbonyl, ethoxycarbonyl, tert-butoxycarbonyl, 1,1-dimethylpropoxycarbonyl, isopropoxycarbonyl, - 25 isobutyloxycarbonyl, diphenylmethoxycarbonyl, 2,2,2 -trichlofoethoxycarbonyl,- 2,2,2 -tribromoethoxy carbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 2-(phenylsulfonyl)ethoxycarbonyl, 2-(triphenylphosphonio)ethoxycarbonyl, 2-furfuryloxycarbonyl, 1-adamantyloxycarbonyl, vinyloxycarbonylrallyloxycarbonyl,~ - benzylthiocarbonyl, 4-ethoxy-l-naphthyloxycarbonyl, 8-quinolyloxycarbonyl, acetyl, formyl, chloroacetyl, dichloroacetyl, trichloroacetyl, trifluoroacetyl, methoxyacetyl, - : - phenoxy acetyl, pivaloyl, benzoyl, methyl, tert-butyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 1 , 1 -dimethyl-2-propenyl, 3-methyl-3-butenyl, allyl, benzyl,. _ ^,__^= para-methoxybenzyl, 3,4-dimethoxybenzyl, diphenylmethyl, triphenylmethyl, tetrahydrofuryl, tetrahydropyranyl, tetrahydrothiopyranylrmethoxymethyl, methylthiomethyl, . 35 ' benzyloxymeT:hyl72-methoxyethoxymethyl, 2,2,2-trichloroethoxymethyl, 2- : — — — (trimethylsilyl)ethoxymethyl, 1-ethoxyethyl; alkylsulfonyl, methanesulfonyl, — — para-toluenesulfonyl, trimethylsilyl, triethylsilyl, triisopropylsilyl, diethylisopropyjsilyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, diphenylmethylsilyl, and tert- butylmethoxypheny lsily 1.

The term "nitro," as used herein, refers to -N02.

The term "organic component," as used herein, refers to a solvent which is not reactive with the starting materials and in which the starting materials are at least partially soluble. Examples of organic components include, C2-C5 alkylamides such as formamide, N,N-dimethylformamide, Ν,Ν-dimethylacetamide, and the like; C4-C6 dialkoxyalkyls such as DME, 1 ,2-diethoxyethane, and the like; Cj-C4 alcohols such as methanol, ethanol, propanol, iso-propanol, butanol, iso-butanol, sec-butanol, tert-butanol, and the like; C3-C10 ketones such as acetone, 2-butanone, 3-pentanone, 2-butanone, 2-pentanone, 2,5-heptanedione,.and the like;.C5-C7Jiydrocarbons such as pentane, hexane, heptane, and the like; optionally substituted aromatic hydrocarbons such as benzene, toluene, 1 ,4-dichlorobenzene, nitrobenzene, and the like; ethers such as diethyl ether, diisopropyl ether, and the like; and esters such as ethyl acetate isopropyl acetate, and the like.

The term "oxo," as used herein, refers to a group formed by the replacement of two hydrogen atoms on the same carbon atom with a single oxygen atom.

The term "palladium catalyst," as used herein, refers to optionally supported palladium such as palladium metal, palladium metal on carbon, and palladium metal on ~ " ' acidic, basic, or neutral alumina; palladium(O) complexes such as tetrakis(triphenylphosphine)palladium(0); palladium salts such as palladium(II) acetate or palladium(II) chloride; and palladium(II) complexes such as allylpalladium(Il) chloride dimer, (1 ,1 '-bis(diphenylphosphino)fenOcene)-dichloropalladium(II), bis(acetato)bis(triphenylphosphine)palladium(II), and bis(acetonitrile)dichloropalladium(II). The term -"C j-C6 perfluoroalkyl," as used herein, refers to a C)-C6 alkyl group, wherein all of the hydrogen radicals have been replaced by fluoride radicals.

The term "protected hydroxyl," as used herein, refers to a hydroxy 1 to which is attached a hydroxyl protecting group. - — — — -- The term "reducing agent," as used herein, refers to boranes, silanes and stannes. _J_ F F F _ : ; j ; The term "silane," as used herein, refers to Si(R )(R )3, wherein R is hydrogen, and each RF is independently hydrogenrC^G^alky^C^e^o alkenyl, aryl, or heteroaryl.

Specific examples of silanes include diethylsilane, dimethylisopropylsilane,"tributylsilane, cyclohexyldimethylsilane, diisopropyloctylsilane, triisopropylsilane, dimethylethylsilane, dimethyloctadecylsilane, triethylsilane, and the like. p _ _p _ p The term "stannane," as used herein, refers to Sn(R )~(R~ )3, wherein R is hydrogen, and each RF is independently hydrogen -G1-C2o alkyl, C2-C20 alkenyl, aryl, or heteroaryl.

Specific examples of stannanes include diethylstannane, dimethylisopropylstannane, tributylstannane, cyclohexyldimethylstannane, diisopropyloctylstannane, triisopropylstannane, dimethylethylstannane, dimethyloctadecylstannane, triethylstannane, and the like.

- The term "sulfide salt," as used [ herein, refers to lithium sulfide, lithium hydrosulfide, sodium sulfide, sodium hydrosulfide, potassium sulfide, potassium hydrosulfide, and the like. The sulfide salts of this invention can be optionally hydrated. _ The term " hydro lyzing agent," as used herein, refers to alkoxide salts, thioalkoxide salts, optionally hydrated sulfide salts, and mixtures thereof.

The term " iodide salt," as used herein, refers to alkali metal iodides, alkali earth metal iodides, and tetraalkylammonium iodides.

The term " tetraalkylammonium iodide," as used herein, refers to compounds of formula [(RB)4N]+[I]\ wherein RB is C , -C20 alkyl.

The term "thioalkoxide salt," as used herein, refers to [M]+[SRA] , wherein M is Li, Na, or K, and RA is CrC6 alkyl.

Asymmetric centers exist in the compounds of this invention. This invention contemplates stereoisomers and mixtures thereof. Individual stereoisomers of compounds are prepared by synthesis from starting materials containing the chiral centers or by preparation of mixtures of enantiomeric products followed by separation such as conversion to a mixture of diastereomers followed by separation or recrystallization, chromatographic techniques, or direct separation of the enantiomers on chiral chromatographic columns. Starting compounds of particular stereochemistry are either commercially available or are made by the methods described herein and resolved by techniques well-known in the art.

: Percentages such as mole% and %C1 impurity were obtained by HPLC analyses of ~ starting materials and productsr^Values- were calculated from the the peak area. - All of the processes of this invention can be conducted as continuous processes. The term "continuous process," as used herein, refers to the conduction of a reaction to provide an intermediate followed by-use, optionally- in-situ of the intermediate, without isolation, in a subsequent reaction. The term "in situ," as used herein, refers to use of an intermediate in the solvent in which the intermediate was prepared without removal of the solvent.

^Abbreviations ' '" i:..' Abbreviations which have been used are: DBN for l,5-diazobicyclo[4.3.0]non-5-ene; . DBU for l,8-diazobicyclo[5.4.0]undec-7-ene; DBA for dibenzylidine acetone; DMA for N,N- dimethylacetamide^DME for dimethoxy ethane; DMF for Ν,Ν-dimethylformamide; HPLC for high pressure liquid chromatography; and THF for tetrahydrofuran.

Synthetic Methods The methods of this invention will be better understood in connection with the following synthetic scheme which illustrates an embodiment of this invention. It will be readily apparent to one of ordinary skill in the art that the compounds of this invention can be prepared by substitution of the appropriate reactants and agents in the synthesis shown below. It will also be apparent to one skilled in the art that the order of the steps themselves can be varied. 1 1- (6) (7) In one embodiment or Scheme 1, conversion of compounds of formula (1) to compounds of formula (2) can be achieved byrreaction of the former and an oxidizing agent acid in a solvent such as Cj-C4 alcohols, THF, dioxane, mixtures thereof, and mixtures" of ~ ~" these solvents with water. Although the reaction generally proceeds at room temperature, it can be run at lower or higher temperatures, as needed. The reaction time is generally about 1 hour to about 18 hours and can be selected depending on the types of starting materials^and.^ the reaction temperature. In a preferred embodiment, this conversion is achieved by reaction of compounds of formula (1) in aTHF/watermixture and periodic acid at about 0 °C to about °C ~f0r abbut 3 hours. " . The conversion of compounds of formula (2) to compounds of formula (3) can be achieved by reaction of the former and an alkanoyl halide in a solvent such as pyridine, diisopropylethylamine, triethylamine, THF, dioxane, benzene, toluene, diethyl ether, C2-C5 alkylamides, C3-C20 ketones, or mixtures thereof. Since acid is liberated with the progress of the reaction, it is preferable to run the reaction with at least a stoichiometric amount of base such as diisopropylethylamine, pyridine, or triethylamine. Although the reaction generally proceeds at lower temperature, it can be run at room temperature, as needed. The reaction time is generally about 30 minutes to about 5 hours and can be selected depending on the types of starting materials and the reaction temperature. In a preferred embodiment, this conversion is achieved by reaction of compounds of formula (3) in acetone and triethylamine at about -10 °C to about 0 °C and an alkanoyl chloride for about 30 minutes.

The conversion of compounds of formula (3) to compounds of formula (5) can be achieved by reaction of the former and compounds of formula (4) and an iodide salt such as an alkali metal iodide, an alkali earth metal iodide, or a tetraalkylammonium iodide in solvents such as water, C2-C5 alkylamides, C4-C6 dialkoxyalkyls, CrC4 alcohols, C]-C4 haloalkyls, C3-C10 ketones, or mixtures thereof. Since acid is liberated with the progress of the reaction, it is preferable to run the reaction with at least a stoichiometric . amount of a first base such as diisopropylethylamine, pyridine, or triethylamine." Compounds of formula (4) are available commercially or can be prepared by means well known in the art (Tetrahedron, 1980, 36(4), 539; Chem. Ber. 1980, 1 13(5), 1898; and Justus Liebigs Ann.

Chem., 1954, 590, 123). The reaction generally proceeds at about 0 °C to about 30 °C for about 1 hour to about 48 hours, depending on the reaction temperature and the nature of the reactants. In a preferred embodiment, this conversion is 25 -achieved by reaction of compounds offormula (3) and compounds of formula (4), ""~ triethylamine, and sodium iodide in 2-butanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3), for — — about 24 hours. ... .... . _■ The conversion of compounds of formula (5) to compounds of formula (6) can be achieved by reaction of the former and a hydrolyzing agent such as an alkoxide salt, a thioalkoxide salt, an optionally-hydrated-sulfide salt, or a mixture thereof in solvents such as water, C2-C5 alkylamides, C4-C6 dialkoxyalkyls, C3-C10 ketones, or mixtures thereof.

. The reaction generally proceeds at about -40 °C to about 35 °C for about 1 hour to about 12 hours, depending on the reaction temperature and the nature of the reactantsr-In a preferred — embodiment, this conversion is achieved" by "reaction of compounds of formula (5) and sodium hydrosulfide hydrate-in-DMA at about 0 °C to about 5 °C for about 2 hours then at ' -13- - ■ - - — — room temperature for about 2 hours. The carbothioic acid salt thus formed can be acidified with an acid such as hydrochloric, hydrobromic, sulfuric, sulfonic, phosphoric, or trifluoroacetic or used directly in the next step without acidification.

The conversion of compounds of formula (6) to compounds of formula (7) can be achieved by reaction of the former and chlorofluoromethane in a C2-C5 alkylamide solvent such as DMF or DMA. The reaction generally proceeds at about -20 °C to about °C for about 1 hour to about 12 hours, depending on the reaction temperature and the nature of the reactants. If the carbothioic acid salt has been acidified, then acid will be liberated during the course of the conversion, and the reaction is run in the presence of a second base such as sodium bicarbonate, potassium bicarbonate, sodium carbonate, or potassium carbonate. If the carbothioic acid salt has not been acidified, then the compounds of formula (6) can be reacted with chlorofluoromethane .withoutjsolation or purification. In a preferred embodiment, this conversion is achieved as a continuous process by in situ reaction of compounds of formula (6) and chlorofluoromethane as a solution in DMA at about 0 °C for about 3 hours then at room temperature and atmospheric pressure for about 12 hours.

In one embodiment of Scheme 1, the compound of formula (1) is commercial grade flumethasone; the compound of formula (2) is 6a,9 -difluoro- 1 1 β, 17a-dihydroxy- 16a-methyl-3-oxoandrosta-l ,4-diene-17 -carboxylic acid; the compound of formula (3) is 6α,9α-difluoro-11 β-hydroxy-l 6a-methyl-3-oxo-l 7a-(propionyloxy)androsta-l ,4-diene- 17β-carboxylic acid; the compound of formula (5) is 17β-(Ν,Ν-(dimethylcarbamoyl)thio)carbonyl-6a,9a-difluoro-l 1 β-hydroxy-l 6a-methyl-l 7a-propionyloxy-3-oxoandrosta-l,4-diene; and the compound of formula (7) is 6a,9a-difluoro-17a-(((fluoromethyl)sulfanyl)-carbonyl)- 1 1 β-hydroxy- 16a-methyl-3 -oxoandrosta- 1 ,4-dien-l_7a-yl, propionate. Any one of these compounds can be reacted with a palladium catalyst and an additive, optionally in the presence of a reducing agent, in a solvent such as a C2-C5 - --alkylamide, a C4-C6 dialkoxyalkyl, an optionally substituted aromatic hydrocarbon, a C,-C4 haloalkyl a C3-C10 ketone, or a mixture thereof, to facilitate the removal the CI impurity-introduced-by the-commercial grade flumethasone. The palladium catalyst · — includes optionally supported palladium such as palladium metal, palladium metal on carbon, and palladium metal on acidic, basic, or neutral alumina; palladium(0)~cornplexes such as ' tetrakis(triphenylphosphine)palladium(0); palladium salts such as palladium(H)-acetate or~ palladium(II) chloride; and palladium(II) complexes such as allylpalladium(II) chloride dimer, (l,r-bis(diphenylphosphino)feiTocene)-dichloropalladium(II), bis(acetato)bis(triphenylphosphine)palladium(II), and bis(acetonitrile)dichloropalladium(II). Additives_useful for this reaction include tri(alkyl)phosphines such as trimethylphosphine7 triethylphosphine,'tributylphosphine, and the like; tri(cycloalkyl)phosphines such as tricyclopropylphosphine, tricyclohexylphosphine, and the like; tri(aryl)phosphines such as triphenylphosphine, trinaphthylphosphine, and the like; tri(heteroaryl)phosphines such as tri(fury-2-yl)phosphine, tri(pyrid-3-yl)phosphine, and the like; tri(alkyl)phosphites such as trimethylphosphite, triethylphosphite, tributylphosphite, and the like; tri(cycloalkyl)- 5 phosphites such as tricyclopropylphosphite, tricyclohexylphosphite, and the like; tri(aryl)phosphites such as triphenylphosphite, trinaphthylphosphite, and the like; and tri(heteroaryl)phosphites such as tri(fury-2-yl)phosphite, tri(pyrid-3-yl)phosphite, and the like. Other additives useful for this reaction include bidentate phosphines such as 1 ,4- bis(diphenylphosphino)butane (dppb), 1 ,2-bis(dipheriyl-phosphino)ethane (dppe), 1 ,1 - 10 bis(diphenylphosphino)methane (dppm), l ,2-bis(dimethyl-phosphino)ethane (dmpe), 1 ,1'- bis(diphenylphosphino)ferrocene (dppf), and the like. Reducing agents useful for this reaction include boranes such as diborane, 9-borabicyclo[3.3.1]nonane (9-BBN), dilongifoylborane, thexylborane, catecholborane, sodium borohydride, tetrabutylammonium borohydride, borane-4-methylmorpholine complex, borane-4-ethylmorpholine complex, borane-dimethylsulfide complex, borane-triethylamine complex, borane-pyridine complex, borane-2,6-lutidine complex, and the like; silanes such as diethylsilane, dimethylisopropylsilane, tributylsilane, cyclohexyldimethylsilane, diisopropyloctylsilane, triisopropylsilane, dimethylethylsilane, dimethyloctadecylsilane, triethylsilane, and the like; and stannanes such as diethylstannane, dimethylisopropylstannane, tributylstannane, cyclohexyldimethylstannane, diisopropyloctylstannane, triisopropylstannane, dimethylethylstannane, dimethyloctadecylstannane, triethylstannane, and the like. The reaction generally proceeds at about 0 °C to about 100 °C for about 10 minutes to about 12 hours, depending on the reaction temperature and whether the reducing agent is employed.

A summary of the reaction conditions useful for removing the CI impurity from flumethasone is described in Table 1 , Table 2, and Table 3. -The initial %Gl-impurity (mole% (before)) in the commercial grade flumethasone used for each of the reactions described in Table 1, Table 2, and Table 3 was determined to be about 0.7. The mole% CI impurity (after) — .. . . _in the commercial grade- flumethasone was then determined-after treatment with-the catalyst and the additive in the presence of a¾ducih]g~agenf The mole percentages (mole%) of catalyst, additive, and reducing agent were calculated based on the moles of commercial grade flumethasone containing the 0.7 mole% CI impurity. For example: 1 mole% palladium catalyst is 1 mole of palladium, catalyst per 100 moles of commercial grade flumethasone; 2 mole% of additive is 2 molesof additive per 100 moles of commercial grade flumethasone; 20 mole% of reducing agent is 20 moles of reducing agent per 100 moles of commercial grade flumethasone; and so forth. · ._..

Table 1 Reaction was conducted using 1 mole% palladium(II) acetate, 2 mole% monodentate additive or 1 mole% bidentate additive and 26 mole% triethylsilane in DMF at 22 °C.

Reaction was conducted using 1 mole% palladium(II) chloride, 2 mole% monodentate additive or 1 mole% bidentate additive and 26 mole% triethylsilane in DMF at 22 °C.

Reactions were- conducted in DMA at.22 °.C.

Table 3 Reactions were conducted in DMF at 22 °C.

*Estimated value due to overlap of the CI impurity with an unknown impurity.

In a preferred embodiment of the invention, the palladium catalyst is present in about 0.3 mol% to about 5 mol% of commercial grade flumethasone; the additive can be present in about 0.8 mol% to about 15 mol% of commercial grade flumethasone; and the reducing agent can be present in about 1 mol% to about 30 mol% of commercial grade flumethasone.

In one particularly preferred embodiment of the invention, palladium(II) acetate is present in about 1 mol% of commercial grade flumethasone; triphenylphosphine is present in about 2 mol% of commercial grade flumethasone; and triethylsilane is present in about 13 mol% of commercial grade flumethasone.

— - — The invention will now be described in connection with other particulaily~pieferred embodiments of Scheme 1 , which are not intended to limit its scope. On the contrary, the invention covers all alternatives, modifications, and equivalents which are included within the scope of the claims. Thus, the following examples will illustrate an especially preferred - practice of the invention, it being understood that the examples are for the purposes of illustration of certai preferred embodiments and are presented to provide what is believed to be the most useful and readily understood description of its procedures and conceptual aspects. ' -~ -17-- - ' - Example 1 6a,9a-difluoro- 11 β, 17a-dihydroxy- 16a-methyl-3 -oxoandrosta- 1 ,4-diene- 17 β-carboxylic acid 5 A mixture of commercial grade Flumethasone (100 g, 243.6 mmoles), palladium(II) acetate (0.552 g, 2.46 mmol) and triphenylphosphine (1.284 g, 4.89 mmol) in DMA (500 mL) at 60 °C was stirred for 30 minutes; cooled to 15 °C and treated with water (2.0 L) over 1 hour; cooled to 0 °C, stirred for 2 hours, and. filtered to provide a solid. The solid was washed with cold water (2x200 mL) and dissolved in THF (500 mL). This solution was cooled to 0 °C, treated with technical grade (approximately 98%) periodic acid (83.3 g, 365.4 mmol) in water (250 mL), stirred for 3 hours, and treated with water (3.75 L); warmed to room temperature, stirred for 30 minutes, and filtered to provide a solid. This solid was washed with water (500 mL) until the pH of the wash was greater than 5 and dried under vacuum at 60 °C with a nitrogen purge to provide 96.6 g (98%) of the desired product.

. . ' · . . . . Example 2 6a,9a-difluoro- 1 1 β-hydroxy- 16a-methyl-3 -oxo- 17a-(propionyloxy')androsta- 1 ,4-diene- 17B- carboxylic acid A solution of Example 1 (95.2 g, 240 mmol) and triethylamine (55.9 g, 552 mmol) in -20— .acetone (1.45 L) at -15 °C was treated with pre-distilled propionyl chloride (51.1 g, 552 mmo rs irred for T^hour treated with diethylamine (52.7 g, 720 mmol), stirred for 1 hour, and treated with 1M HCl (1.90 L); warmed to 0 °C, stirred for 1 hour, and filtered. The solid was washed with water (475 mL), dried for 12 hours at 60 °C under vacuum with a nitrogen - purge and treated sequentially with 3-pentanone (459 mL), 2-butanone ( 1 mL), and water (5.1 mL). This mixture was heated to reflux for one hour; cooled to room temperature over two hours, stirred for 18 hours, and filtered to provide a solid.~This solid was washed with 3- pentanone (100 mL) and dried under vacuum with a nitrogen~purge~at~607°Cibri 8 hours to provide 86.7 g. (7.9.8%) of the desired product.

Example 3 17 - N,N-Cdimethylcarbamoyl')thio')carbonyl-6a.9 -difluoro- 1 1 β-hvdroxy- 16a-methyl- 17a- propionyloxy-3-oxoandrosta-L4-diene A solution of Example 2 (86.7 g, 192_mmol) and N,N-dimethylthiocarbamoyl chloride (47.5 g, 384 mmoles) in 2-butanone (2.17 L) at room temperature was treated sequentially with triethylamine (42.7 g, 422 mmoles), anhydrous sodium iodide (28.8 g, 192 mmol), and water (8.67 mL, 10% w/w with Example 2), stirred for 2 hours, treated sequentially with DMA (694 mL) and water (4.34 L); cooled to 0 °C, stirred for 2 hours, and filtered to provide a solid. The solid was washed with water (500 mL) and dried at 60 °C under vacuum with a nitrogen purge to provide 96.4 g (93%) of the desired product.

Example 4 : 6a,9a-difluoro-l 7a-(((fluoromethyl)sulfanv0carbony0-l 1 β-hydroxy-l 6a-methyl-3- oxoandrosta-1.4-dien-17a-yl propionate (fluticasone propionate) A solution of Example 3 (96.4 g, 179 mmol) and sodium hydrosulfide hydrate (45.3 g, 808 mmol) in dimethylacetamide (386 mL) at 0 °C was stirred for 2 hours; warmed to room temperature and stirred for 2 hours; cooled to -5 °C, treated slowly with a solution of chlorofluoromethane (92.7 g, 1.354.mol) in dimethylacetamide (313 mL), and stirred for 4 hours; warmed to room temperature, stirred for 18 hours and treated slowly with a solution of sodium bicarbonate (29.9 g) in water (1.45 L); cooled to -5 °C, stirred for two hours, and filtered to provide a solid. The solid was washed sequentially with water J145 mL) and 1-butanol (145 mL) and treated with ethyl acetate (540 mL) and 1-butanol (2.16 L) to provide a mixture. The mixture was heated to reflux for 40 minutes and filtered hot (without rinsing)-through a less than 1 micron filter. The filtrate was stirred while H~ "cooling toTobrn temperature, stirred for eight hoursrand filtered to provide a solid.-This solid was washed with 1-butanol, (145 mL), recrystallized from 1-butanol (2.70 L), and dried under vacuum with a nitrogen purge at 60 °C to provide 62.7 g (70%) of the desired product.

Example 5 — ■ - 17B-(N,N-(dimethylcarbamoyl thio carbonyl-6a,9a-difluoro-1 1 -hydroxy-16a-methyl-17a- acetyloxy-3 -oxoandrosta- 1 ,4-diene . . ' . . A solution of 6a,9ardifluoro-l 1 β-hydroxy-l 6a-methylr3-oxo- 17a- (acetyloxy)andrdsta-l,4-diene-17p-carboxylic acid (4.85 g, 1 1.1 mmol), Ν,Ν-dimethylthiocarbamoyl chloride (2.73 g,22.2 mmol) in 2-butanone (122 mL) at room temperature was treated sequentially with triethylamine (3.4 mL, 24.4 mmol), anhydrous sodium iodide (1767 ^7^1 l Fmmol), and water (0.5 rhL, 10% w/w with the carboxylic acid), -19- - · ■■- ' - stirred for 12 hours, treated sequentially with DMA (40 mL) and water (242 mL); cooled to 0 °C, stirred for 1 hour, and filtered to provide a solid. The solid was washed with water and dried at 60 °C under vacuum with a nitrogen purge to provide 5.81 g (90%) of the desired . product. . . .... ς Example 6 6 Example 7 17 -(OSf,N-dimethvlcarbamoynthiocarbonylV9a-fluoro- 1 1 β-hvdroxy- 17a- CpropionvloxYV16a-methyl androstat-l ,4-diene-3-one A solution of 9a-fluoro- 11 β-hydroxy- 17a-(propionyloxy)- 16a-methyl-3 - oxoandrostat- r,4-diene-17 -carboxylic acid (10.0 g, 23.04 mmol) and N,N-dimethylthiocarbamoyl chloride (5.67 g, 46.08 mmol) in dichloromethane (130 mL) at room temperature was treated sequentially with triethylamine (6.5 mL, 46.08 mmol) and anhydrous sodium iodide (3.45 g, 23.04 mmol), stirred for 12 hours, and filtered through diatomaceous earth (Celite®) with dichloromethane ( 25 mL). The filtrate was concentrated under reduced pressure. The concentrate was treated sequentially -with . DMA_(1.5DLmLX and water (190 mL); cooled to 0 °C, and stirred for 1 hour. The resulting solid was collected by ; filtration, washed with water, and dried under vacuum at 60 °C with a nitrogen purge to provide 10.2 g, (85%) of the desired product.

Example 8 9a-fluoro-l 1 β-hydroxv-l 7a-fpropionyloxy -l 6a-methyl-3-oxoandrostat-l ,4-diene-l 7B- thiocarboxylic acid -. ·;·. ——·--- A solution of Example 7 (5.0 g, 9.58 mmol) in DMA.(50 mL) at -15 °C was treated .: 1. with sodium thiomethoxide (0.74 g, 10.54 mmol) in one portion, stirred for 2 hours; warmed to 0 °C, treated wim cold-lM-H ltl O mL), stirred for 1 hour at 0 °C, and filtered. The resulting solid was washed with water until the wash was pH 6 or higher and dried under vacuum at 60 °C with a nitrogen purge to provide 4.10 gV"(95%)^fthe~desired product. - -;■ ■ -■- ™—-—- -: " " -20- . ■ · , '. '..· : ..:- . ■ - ■ ■ - - ·· . ' . . ·· -- -■■ ' ' - -" . . - : ■■- . - . ~ " " . . ■ ■ . · --.—· —'—- ■ .... ■ ;- ....- ..- .' ■ · - .._ : — --·— · . . · . ÷- .--·..

It will be evident to one skilled in the art that this invention is not limited to the forgoing examples, and that it can be embodied in other specific forms without departing from the essential attributes thereof. Thus, it is desired that the examples be considered as illustrative and not restrictive, reference being made to the claims, and that all changes which come within the meaning and range of equivalency of the claims be embraced therein. _ -21·-

Claims (8)

1. 42,568/4 wherein the symbol = represents a single bond or a double bond; one of R1 or R2 is hydrogen and the other is optionally protected hydroxyl; or R1 and R2 together are oxo; R3 and R4 are independently hydrogen or halide; and R5 and R6 are independently CrC6 alkyl; the method comprising: (c) reacting a compound of formula (3) wherein R7 and R8 are independently C C6 alkyl; or R7 and R8 together are C C6 alkylene, in a solvent comprising 2-butanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3) to provide a compound of formula (5) 22 142,568/3 (d) reacting the product of step (c) and NaSH to provide a compound of formula (6) (e) reacting the product of step (d) and acid; (f) reacting the product of step (e) and chlorofluoromethane optionally in the presence of a second base; and (g) optionally deprotecting the product of step (f).

2. The method of claim 1, wherein the first base is a carbonate salt, an amine, or a mixture thereof.

3. The method of claim 1, wherein the iodide salt is an alkali metal iodide, an alkali earth metal iodide, or a tetraalkylammonium iodide.

4. The method of claim 1, wherein the second base is a carbonate salt.

5. A method for the preparation of a compound of formula (7) 23 142,568/3 wherein the symbol = represents a single bond or a double bond; one of R1 or R2 is hydrogen and the other is optionally protected hydroxy I; or R' and R2 together are oxo; R3 and R4 are independently hydrogen or halide; and R5 and R6 are independently C|-C6 alkyl; the method comprising: (b) reacting a compound of formula (2) and an alkanoyl halide and the first base to provide the compound of formula (3) (c) reacting a compound of formula (3) and a first base, an iodide salt, and a compound of formula (4) 24 142,568/4 wherein R7 and R8 are independently CrC6 alkyl; or R7 and R8 together are CrC6 alkylene, in a solvent comprising 2-butanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3) to provide a compound of formula (5) (d) reacting the product of step (c) and NaSH to provide a compound of formula (6) (e) reacting the product of step (d) and acid; (f) reacting the product of step (e) and chlorofluoromethane optionally in the presence of a second base; and (g) optionally deprotecting the product of step (f).

6. A method for the preparation of a compound of formula (7) 25 142,568/2 wherein the symbol == represents a single bond or a double bond; one of R1 or R2 is hydrogen and the other is optionally protected hydroxyl; or R1 and R2 together are oxo; R3 and R4 are independently hydrogen or halide; and R5 and R6 are independently C1-C6 alkyl; the method comprising: (c) reacting a compound of formula (3) and a first base, an iodide salt, and the compound of formula (4) wherein R7 and R8 are independently CrC6 alkyl; or R7 and R8 together are CrC6 alkylene, in a solvent comprising 2-butanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3) to provide a compound of formula (5) 26 142,568/1 (d) reacting the product of step (c) and NaSH to provide a compound of formula (6) (e) reacting the product of step (d) and chlorofluommethane; and (f) optionally deprotecting the product of step (e).

7. A method for the preparation of a compound of formula (7) wherein the symbol = represents a single bond or a double bond; one of R1 or R2 is hydrogen and the other is optionally protected hydroxyl; or R1 and R2 together are oxo; R3 and R4 are independently hydrogen or halide; and R5 and R6 are independently CrC6 alkyl; the method comprising: (b) reacting a compound of formula (2) 27 142,568/2 and a first base, an iodide salt, and a compound of formula (4) wherein R7 and R8 are independently Ci-C6 alkyl; or R7 and R8 together are CrC6 alkylene, in a solvent comprising 2-hutanone and water, the water present in about one quarter percent by weight to about ten percent by weight of the compound of formula (3) to provide a compound of formula (5) 28 142,568/2 (e) reacting the product of step (d) and chlorofluoromethane; and (f) optionally deprotecting the product of step (e).

8. The method according to any one of claims 1 -7, substantially as herein described with reference to the examples. g:\petros2008\8878\l 19\amended claims.doc/np* 29