PREPARATION OF (11 beta ,16 beta )-21-(3-CARBOXY-3-OXOPROPOXY)-11-HYDROXY-2'-METHYL-5'H-PREGNA-1,4-DIENO[17,16-D]OXAZOLE-3,20-DIONE

Abstract: A process for preparing the compound (11 beta ,16 beta )-21-(3-carboxy-3-oxopropoxy)-11-hydroxy-2'-methyl-5'H-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione which comprises reacting the compound (11 beta ,16 beta ,-11,21-dihydroxy-2'-methyl-5'H-pregna-1,4-dieno[17,16-d]oxazole-3,20-dione with succinic anhydride in a (C1-C4)alkyl ester of a (C1-C4) carboxylic acid as solvent, in the presence of a basic catalyst.

Description: PREPARATION OF (llβ,16β)-21-(3-CARBOXY-3-OXOPROPOXY)-11- HYDROXY-2'-METHYL-5'H-PREGNA-1,4-DIENO[17 ,16-DJOXAZOLE- 3,20-DIONE The present invention refers to a new process for preparing the compound of formula I i.e. (llβ,16β)-21- (3-carboxy-3-oxopropoxy) -11-hydroxy- 2 ' -methyl-5 Η-pregna-1, 4-dieno[17, 16-d]oxazole-3, 20- dione. The above compound is a water soluble ester of deflazacort (INN - International Nonproprietary Name) , wherein the acetate moiety on the C-21 of deflazacort is substituted by an hemisuccinate moiety. Deflazacort is a compound employed in therapy since some years as a calcium-sparing corticoid agent. These compounds belong to the more general class of pregneno-oxazolines, for which anti-inflammatory, glucocorticoid and hormone-like pharmacological activities are reported. Examples of compounds of the above class, comprising deflazacort, are disclosed in US 3413286. EP-B-322630 discloses a fermentation process for preparing the (llβ, 16β) -11, 21-dihydroxy-2 ' -methyl-5 'H- pregna-1, 4-dieno[17, 16-d]oxazole-3 , 20-dione, which corresponds to the compond of formula I bearing a hydroxy group in place of the emisuccinate moiety at the position 21. This compound is referred to in the above patent as llβ-21-dihydroxy-2 ' -methyl-5 'βH-pregna-1, 4- dieno[17 , 16-d-]oxazoline-3 , 20-dione and can be represented by the following formula II: US 4440764 discloses the compound of formula I, with the name llβ-21-dihydroxy-2 ' -methyl-5 *βH-pregna-1, 4- dieno [17 , 16-d] oxazole-3 , 20-dione 21-hemisuccinate, and a process for its preparation, which comprises reacting the compound of formula II with a molar excess of succinic anhydride (from 0.1 to 5 times) in an organic solvent and in the presence of a basic catalyst. Among the cited organic solvents are halogenated lower aliphatic hydrocarbons, acetone, ethyl acetate, dimethylformamide and acetonitrile; as the basic catalyst, 4- (N,N-diethylamino)pyridine is specifically mentioned; alternatively, organic solvents may be employed which act both as reaction solvents and basic catalysts, such as pyridine, collidine, picoline and mixtures thereof. The product can be recovered by washing the reaction mixture with an acidic solution and then cristallyzing the end product from a suitable solven . in particular, methylene chloride can be employed as the organic solvent and 4- (N,N-diethylamino)pyridine as the catalyst; after the reaction is completed, the reaction mixture is then washed with aqueous 1% HCl and water and then diluted with toluene. The reaction solvent is distiled off and the product crystalizes in toluene upon cooling. It has now been found that, by using a (C 1 -C 4 )alkyl ester of a (C 1 -C 4 ) carboxylic acid as the reaction solvent, the same reaction solvent can surprisingly be used also for the crystallization of the end-product. The main advantages are a simplification of the preparation procedure and higher yields with respect to the prior art. Furthermore, these solvents, particularly ethyl acetate, are solvents widely accepted in industrial preparations, for what concerns the security, industrial hygiene and enviroment protection. Although all of the other solvents known in the art are good reaction solvents, allowing the quantitative conversion of the compound of formula II into the compound of formula I, none of them is suitable also for cristallizing the final product. For instance, the compound of formula I is too much soluble in halogenated lower aliphatic hydrocarbons (such as methylene chloride) and thus may not be cristallized from those solvents. Likewise, direct cristallization from solvents like dimethylforma mide or acetonitrile is not possible, due to the high solubility of the above compound in these solvents. On the other side, the direct cristallization from acetone gives very poor yields, while a considerable amount of impurities co-cristallize with the desired product. Thus, the process of the invention comprises reacting the compound of formula II with succinic anhydride in a (C 1 -C 4 ) alkyl ester of a (C 1 -C 4 ) carboxylic acid in the presence of a basic catalyst. The starting material of formula II is obtained according to the procedures known in the art, for instance according to the fermentation process disclosed in the above cited EP-B-322630, here incorporated by reference. Said patent discloses a fermentation process for obtaining the compound of formula II, wherein a 2 ' -methyl-4-pregnen-21-ol- [17α, 16α-d-] oxazolinyl-3, 20- dione is contacted with a sequentially growing mixed culture of a Curvularia strain and an Arthrobacter strain. More in particular, according to a preferred embodiment, the above compound is added to a growing culture of C. lunata NRRL 2380 in a suitable fermentation medium after 12-24 hours from inoculum, and, after 48-72 hours from inoculum, a growing culture of A. simplex ATCC 6946 of 18-36 hours is added to the mixture and further cultivated for 40-55 hours; the fermentation is carried out under submerged conditions, temperature is kept between 27°C and 32°C and pH between 6 and 8; the fermentation product of formula II is recovered according to procedures known in the art. Examples of (C 1 -C 4 )alkyl esters of a (C 1 -C 4 ) carboxylic acids are the following: methyl, ethyl, propyl, iso-propyl, butyl, 2-methylpropyl or t-butyl for iate; methyl, ethyl, propyl, iso-propyl, butyl, 2- methylpropyl or t-butyl acetate; methyl, ethyl, propyl, iso-propyl, butyl, 2-methylpropyl or t-butyl propionate; methyl, ethyl, propyl, iso-propyl, butyl, 2-methylpropyl or t-butyl butirrate; methyl, ethyl, propyl, iso-propyl, butyl, 2-methylpropyl or t-butyl iso-butirrate. Particularly preferred is ethyl acetate. The reaction temperature may vary from about 0°C to 60°C; preferably it will be in the range from 15°C to 35°C, particularly preferred being room temperature. The succinic anhydride is preferably reacted with the compound of formula II in a molar excess with respect to the stoichometric ratio; preferably, the molar ratio between the compound of formula II and succinic anhydride is from about 1÷2 to about 1÷5, particularly preferred being a molar ratio of about 1.0÷2.5. Basic catalysts useful in the present process are tertiary organic aliphatic or alicyclic amines such as trimethylamine, triethylamine (TEA), N-methyl pyrrolidine or heterocyclic bases such as pyridine, 4- (N,N-dimethylamino) -pyridine, 4- (N,N-diethylamino) - pyridine, collidine, picoline, and the like. Preferably, TEA is employed. The amount of catalyst will depend from the specific catalyst employed; in general it will be from about 0.1 to about 3 times the molar amount of the compound of formula II. Preferably its molar amount is from about equimolar to 2 times the molar amount of the compound of formula II; in particular, when the molar ratio between the compound of formula II and succinic anhydride is about 1.0÷2.5 and TEA is the selected catalyst, its molar amount is about 1.5 times the molar amount of the compound of formula II. indication, at room temperature, the reaction is completed in about 18-30 hours. In any case the reaction course can be easily followed according to the standard techniques known in the art, such as by HPLC or TLC usually by following the formation of the final product. Thus, on the basis of the results of these assays, the skilled man is able to evaluate when to stop the reaction and begin the recovery of the desired product. The reaction product is then recovered according to the standard procedures known in the art, which would allow the recovery of the compound of formula I from the same solvent used for the reaction. For instance, the reaction mixture is preferably washed with an aqueous acid solution at a pH of about 2.0-3.5 (e.g. with diluted mineral acids such as chloridric, sulfuric or phosphoric acid) , the organic phase is separated, filtered and then the end-product is recovered, preferably by precipitation upon concentration of the filtered solution to small volume. For better illustrating the invention, the following examples are given. EXAMPLE 1 Preparation of (llβ,16β)-21-(3-carboxy-3-oxopropoxy) -11- hydroxy-2' -methyl-5 'H-pregna-1,4-dieno[17, 16-d]oxazole- 3,20-dione To a stirred solution of llβ-21-dihydroxy-2 ' -methyl- 5 'βH-pregna-1, 4-dieno[17 , 16-d-] oxazoline-3 ,20-dione (10 g, 0.025 mol) in 300 ml of ethyl acetate, 6.2 g (0.062 mol) of succinic anhydride and 5.3 ml (0.038 mol) of TEA are added at room temperature. The reaction is followed by TLC on silica gel using a mixture of chloroform/methanol 9/1 as eluent. After 24 hours, the reaction is considered completed. EXAMPLE 2 Recovery and purification of (llβ,16β) -21- (3-carboxy-3- oxopropoxy)-ll-hydroxy-2 ' -methyl-5*H-pregna-l,4- dieno[17,16-d]oxazole-3,20-dione When the reaction of Example 1 is completed, 100 ml of water are added and the pH is adjusted at a value of about 3 with 10% (w/w) sulfuric acid. The aqueous layer is discarded and the organic layer is filtered and concentrated to a small volume. The suspension is kept at 5°C for 2 hours; after filtration and drying, 11.2 g of cristalline product are obtained. By further concentrating the mother liquors to a smaller volume, further 0.8 g of product are obtained, for a total of 12.0 g and an overall yield above 98%. The above product (12.0 g) is then suspended in 240 ml of apirogen water. The suspension is kept under stirring at 35°C for about 2 hours, cooled at 5°C for about 1 hour and the solid is collected by filtration. After washing with apirogen water and drying, 11.1 g of (llβ, 16β) -21- (3-carboxy-3-oxopropoxy) -ll-hydroxy-2 ' - methyl-5 'H-pregna-1, 4-dieno [17 , 16-d]oxazole-3 , 20-dione are obtained (yield 91%, purity >98%) .

Claims: CLAIMS 1. A process for preparing the compound (llβ, 16β) -21- (3-carboxy-3-oxopropoxy) -ll-hydroxy-2 ' -methyl-5 ' H- pregna-1, -dieno[17, 16-d] oxazole-3 , 20-dione of formula I which comprises reacting the compound (llβ, 16β) -11, 21- dihydroxy-2 ' -methyl-5 'H-pregna-1, 4-dieno [17 , 16- d] oxazole-3 ,20-dione of formula II with succinic anhydride in a (C 1 -C 4 ) alkyl ester of a (C 1 -C 4 ) carboxylic acid as the solvent, in the presence of a basic catalyst. 2. Process according to claim 1 wherein the solvent is ethyl acetate. 3. Process according to claim 1 or 2 wherein the basic catalyst is selected from trimethylamine, triethylamine, N-methyl-pyrrolidine, pyridine, 4- (N,N-dimethylamino) - pyridine, 4- (N,N-diethylamino)pyridine, collidine, picoline. 4. Process according to claim 1 or 2 wherein the basic catalyst is triethylamine. 5. Process according to claim 1 wherein the reaction temperature is from 0°C and 60°C. 6. Process according to claim 1 wherein the reaction temperature is from 15°C and 35°C. 7. Process according to claim 1 wherein the molar ratio between the compound of formula II and succinic anhydride is from 1÷2 to 1÷5. 8. Process according to claim 1 wherein the molar ratio between the compound of formula II and succinic anhydride is about 1÷2.5. 9. Process according to claim 1 wherein the amount of basic catalyst is from 0.1 to 3 times the molar amount of the compound of formula II. 10. Process according to claim 1 wherein the amount of basic catalyst is from equimolar to 2 times the molar amount of the compound of formula II. 11. Process according to any one of claims 1 to 9, which further comprises, after completion of the reaction, washing the reaction mixture with an aqueous acid solution at a pH of about 2.0-3.5, separating and filtering the organic phase and recovering the end¬ product of formula I, preferably by precipitation upon concentration of the filtered solution to small volume. 12. Process according to claim 10 wherein the aqueous acid solution is a solution of a diluted mineral acid.

Inventors: CANCELLIERI CALOGERO, FORTE LUIGI, CANCELLIERI, CALOGERO, FORTE, LUIGI
Applicants: CANCELLIERI CALOGERO, FORTE LUIGI, LEPETIT SPA, CANCELLIERI, CALOGERO, FORTE, LUIGI, GRUPPO LEPETIT S.P.A.
Application year: 1996
Main classification: C07J71
IPC codes: C07J71