Steps for the preparation of 9{60 -fluoro-16-methylene-prednisolone or -prednisonone and 21-esters thereof
United States Patent [191 lrmscher et al.  
 [ Apr. 15, 1975 STEPS FOR THE PREPARATION OF 9a-FLUORO-l6-METHYLENE- PREDNISOLONE OR -PREDN1SONONE AND ZI-ESTERS THEREOF [75] Inventors: Klaus Irmscher; Fritz Von Werder;  
 Karl-Heinz Bork; Hans-Guenther Kraft, all of Darmstadt, Germany [73] Assignee: Merck Patent Gesellschaft mit beschrankter l-laftung, Darmstadt, Germany [22] Filed: Feb. 26, 1973 [21] Appl. No.: 335,735  
 Related U.S. Application Data [63] Continuation-impart of Ser. No. 851,723, Aug. 20,  
 1969, Pat. No. 3,718,542.  
 [56] References Cited UNITED STATES PATENTS 2/1969 Kicslich et al. 260/397.45 1 H1970 Hewitt et al. 260/397.45  
 3,538,131 ll/1970 Ringold et a1. 260/397.45  
 I FOREIGN PATENTS OR APPLICATIONS 970,487 9/1964 United Kingdom 260/39745 Primary Examiner-Elbert L. Roberts Attorney, Agent, or Firm-Millen, Raptes &amp; White [57] ABSTRACT A process having improved yields is provided for the production of 9a-fluoro-16-methy1ene-prednisone or prednisolone and 21-esters thereof, the process comprising at least one of the following steps:  
 a. microbiologically dehydrogenating 9B,  
  1 IB-oxido-l6-methylene-4-pregnene-17a-o1-3,20- dione in the 1(2) position;  
 b. reacting the resultant 93,1 1B-0xido-16-methylene-1,4-pregnadiene- 17a-ol-3,20-di0ne with hydrogen fluoride; and  
 c. reacting the resultant 9a-fluoro-16-methylene-1,4-pregnadiene- 1 lB,170z-dio1-3,20-dione with iodine in an alkaline solution, and thereafter with an alkali metal acetate to form 9a-fluoro-l6-methylene-prednisolone-21-acetate.  
 1 Claim, No Drawings STEPS FOR THE PREPARATION OF 9a-FLUORO-16-METHYLENE-PREDNISOLONE OF -PREDNISONONE AND ZI-ESTERS THEREOF CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 851,723 filed Aug. 20, 1969 now US. Pat. 3,718,542 issued Feb. 27, 1973.  
 BACKGROUND OF THE INVENTION This invention relates in general to steroids, and in particular to a process for the preparation of )afluorol6-methylene-steroids of the following Formula A wherein R, represents aH, BOH or =0, and  
 R represents a free or csterified hydroxy group.  
  These compounds are known and possess interesting pharmacological properties, being especially useful for their anti-inflammatory activities. They can be produced in accordance with German Pat. No. 1,263,765 from lo-methylene-l7a-hydroxy-progesterone (I) or the .l-dehydro-derivative thereof by means of II- hydroxylation, and a number of secondary reactions. A particularly advantageous procedure, according to this German patent, resides in first converting compound I in four stages into 9/3, 1 lB-oxido-l6-methylene-4- prcgncn-l7a-ol-3,20-dione (II); then acetoxylating the latter in the 2l-position to 93,1 lB-oxido-l6- mcthylene-4-pregnene- 1 701,2 1 -diol3 ,20-dione- 2l-acetate (III); reacting (III) with hydrogen fluoride to obtain 9a-fluoro-l6-methylene-hydrocortisone- 2l-acetate (IV); saponifying; microbiologically dehydrogenating in the l(2)-position to 9a-fluoro-l6- mcthylene-prednisolone (V); and optionally oxidizing this compound to the corresponding prednisone derivative and/or esterifying this compound V in the 21- position, for example to the particularly valuable 9afluorol 6-methylenc-prednisolone-Z l -acetate (VI (III IV) 5771 Thus, based on II as the starting material, the total yield of VI was 11.5%.  
 SUMMARY OF THE INVENTION The principal object of the invention is to provide an improved process for the production of steroids of Formula A, and especially to provide an improved process for the production of 9a-fluoro-l6-methylene-prednisolonc-Z l-acetate from 913,1 lB-oxido-l6-methylenci-pregnenel 70Z-ol-3,20-dione.  
  Upon further study of the specification and claims, other objects and advantages of the present invention will become apparent.  
  To attain the objects of the invention, it was quite unexpectedly discovered, that compound VI can be produced from II in a total yield which is almost three times as high (32%), by first dehydrogenating II in the l(2)-position, then reacting with hydrogen fluoride, and conducting the acetoxylation in the 2l-position only at the end, each of the steps contributing to the overall high yield. From the acetate VI, it is possible to obtain, by oxidation and/or saponification, 9a-fluorol6-methylene-prednisone-2l-acetate or the corresponding 2l-OH-compounds, and by esterification thereof, the corresponding 2l-esters.  
 DETAILED DISCUSSION For the production of 9a-fluoro-l6-methyleneprednisolone (v) or -prednisone, and 2l-esters thereof. the process comprises the following steps:  
  a. microbiologically dehydrogenating 9,8,1 lB-oxidol6-methylene-4-pregnen-l7a-ol-3,20-dione (II) in the l (2 )-position;  
  b. reacting the thus-obtained 9B,] lB-oXido-lfimethylene-l,4-pregnadien-l7a-ol-3,20-dione with hydrogen fluoride; and  
  c. treating the thus-produced 9a-fluoro-l6- methylene-1,4-pregnadiene-l 1B,] 7a-diol-3,20-dione with iodine in an alkaline solution and subsequently with an alkali metal acetate.  
  In the thus-obtained 9a-fluoro-l6-methylene-prednisolone-Zl-acetate (VI) the ll-OH-group can be optionally converted into an I l-keto-group by treatment with an oxidizing agent and/or the 2l-acetoxy-group can be optionally saponified by treatment with a saponifying agent with the formation of 9a-fluoro-l6-methylene-prednisolone (V) or -prednisone, and finally, the latter compounds can be optionally converted into the 2l-esters thereof by treatment with an esterification agent.  
  For the microbiological introduction of the l(2)- positioned double bond, the following microorganisms are especially suitable: Bacillus sphaericus, Fusayium sulani, Coryneba&#39;ct&#39;erium simplex, Alternaria sp.. Mycobacteriunz smegmatis, Calonectria decora, Mycobacterium Iacticola, opliiobolus sp., Alcaligenes sp., Did)- mella Iycopersici, Protaminobacter sp., Septomyxa affinis, Nocardia sp., Cylindrocarpon radicioola, Streptomyces lai&#39;endulae, Bacillus qvclooxydans. The fermentation requires about 4-l4 hours, depending on the microorganisms. Particularly suitableare cultures of Bacillus sphaericus var. fusiformis and Corynebacterium simplex.  
  By reacting the resultant 9B,] lB-oxido-l6- methylene-I,4-pregnadien-l7a-ol-3,20-dione with hydrogen fluoride, preferably in a aqueous hydrofluoric acid at C.. there is obtained 9a-fluoro-l6- methylenel ,4-pregnadiene-l 1B, l70z-diol-3,20-dione.  
  To introduce the 2l-acetoxy-group, the last mentioned compound is treated in the usual manner with elemental iodine in an alkaline solution and subsequently with an alkali metal acetate, e.g., potassium acetate. Preferably, the elemental iodine is added to a solution of the steroid in a suitable inert organic solvent, for example a mixture of tetrahydrofuran and methanol, and the reaction solution is thereafter mixed dropwise with aqueous sodium hydroxide solution. The thus-obtained 2l-iodo-compound is then converted, without&#39; isolation, into 9a-fluoro-l6-methyleneprednisolone-2l-acetate (V1) with potassium acetate, e.g. in acetone.  
  The thus-obtained compound Vl or the 9oz-fluoro-l6- methylene-prednisolone (V) producible therefrom by saponification can be oxidized to the corresponding 1 lketo-compounds. Suitable oxidizing agents include, but are not limited to a mixture of CrO and pyridine or a mixture of CrO and H50, in water/acetone (Jones reagent) or hypohalous (hypochlorous or hypobromous) acid.  
  Alternatively, it is also possible to convert 9a-fluorol6-methylene-prednisoloneor prednisone- Zl-acetate, by treatment with a saponification agent, into 9a-fluoro-l6-methylene-prednisolone or prednisone. A suitable saponification agent is, for example, an aqueous solution of sodium bicarbonate. Advantageously, these reactions are conducted under the exclusion of oxygen.  
  Furthermore, 9a-fluoro-l6-rnethylene-prednisolone or&#39;prednisone or the 2l-acetates thereof, can be converted into any desired esters by esterification or ester interchange.  
  Suitable as esterification or interesterification agents are all those acids, or the derivatives thereof, effecting esterification or interesterification, which result in physiologically compatible esters. For example, the following acids or the derivatives thereof suitable for esterification can be employed: carboxylic acids of prefcrably l-l8 carbon atoms, e.g. fatty acids, such as acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, trimethylacetic acid, caproic acid, enanthic acid, caprylic acid, palmitic acid, stearic acid, undecylenic acid, benzoic acid, hexahydrobenzoic acid, cyclopentyl-, cyclohexylor arylacetic acids and propionic acids, such as phenylacetic or phenylpropionic acid, as well as halocarboxylic acids, such as chloroacetic acid, ether acids or heterocyclic acids, such as furancarboxylic acid-(2) or nicotinic acid. If desired, in order to produce water-soluble derivatives, it is also possible to esterify with dicarboxylic acids of preferably 2-18 carbon atoms, aminoor alkylaminocarboxylic acids, or with phosphoric or sulfuric acid. In this manner, the following compounds can be prepared, for example: oxalates, succinates, maleates, tetrahydrophthalates, or the acid addition salts of aminocarboxylic acid esters, such as, for example, aspartic acid esters, or diethylaminoacetic acid esters. Derivatives suitable for esterification are, in addition to the free acids, for example, the halogenides, anhydrides, thiol derivatives, as well as ketenes thereof. For interesterification methods, lower alkyl esters are likewise suitable.  
  The lfi-methylene-corticoids obtained in accordance with the process of.this invention can be employed as antiinflammatory drugs. They are especially suitable for the treatment of rheumatoid arthritis and for com bating persistent allergies and other inflammatory discases of the skin. They are compounded in pharmaceutical compositions and administered in the same manner as the conventional corresponding 16- desmethylene steroids.  
  Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.  
 EXAMPLE a. Microbiological l(2)-Dehydrogenation A culture of Corynebacterium simplex is grown in a lOO-liter fermentation vessel, and at a pH of 6.7 7.0, there is added 30 g. of 913,1lB-oxido-l6-methylene-4- pregnen-l7a-ol-3,20-dione in 950 ml. of methanol. After 7-8 hours of agitation, the reaction is terminated. The liquor is extracted several times with dichloromethane; the combined extracts are concentrated by evaporation, and the residue is mixed with 600 ml. of petroleum ether. After allowing the reaction mixture to stand overnight, the thus-obtained 9B,llB-oxido-l6- methylene-1,4-pregnadien-l7a-ol-3,20-dione is vacuumfiltered, washed with petroleum ether, dried, and recrystallized from acetone; m.p. 229230C.; [01],, 93.2 (chloroform); yield: 78.5%.  
 b. Epoxide Cleavage With Hydrogen Fluoride Under agitation at 20 C., 41.5 g. of 98,1 lB-oxidolo-methylene-1,4-pregnadien-l7a-ol-3,20-dione is introduced in small increments during the course of /2 hour into 104 ml. of aqueous hydrofluoric acid. The reaction mixture is stirred for an additional 2 hours at 20C., and then introduced into a mixture of 664 g. of potassium carbonate, 1 kg. of ice, and 1 kg. of water. The resultant 9a-fluoro-l6-methylene-l,4- pregnadiene-l1B,l7a-diol-3,20-dione is vacuumfiltered, thoroughly washed with water, dried, and recrystallized from acetone; m.p. 295296 C.; [011 4.5 (chloroform); yield: 78.8%.  
 c. Acetoxylation Fifty-eight g. of 9a-fluoro-l6-methylene-l,4- pregnadiene-l 1B,17oz-diol-3,20-dione is suspended in a mixture of 870 ml. of tetrahydrofuran and 522 ml. of methanol. Under agitation and during the course of 2 hours, there are introduced 87 g. of calcium oxide and 87 g. of iodine in small portions. Thereafter, the reaction mixture is stirred for 1 further hour and then introduced into a mixture of 18 l. of water, 6 kg. of ice, and 290 ml. of glacial acetic acid. The precipitate is washed with water, dried at room temperature, and dissolved in 4,750 ml. of acetone. After the addition of 285 g. of potassium acetate, the reaction mixture is boiled for 6 hours, concentrated by evaporation, worked up, and recrystallized from cloroform, thus obtaining 9a fluorol -methylene-prednisolone-2 l-acetate, m .p. 233-234 C.; [12:1 +32 (dioxane); yield: 52.2%.  
 d. Saponification One gram of 9a-fluoro-l6-methylene-prednisolone- 2l-acetate is dissolved in 50 ml. of nitrogen-saturated methanol and mixed. with the introduction of nitrogen, with 2 ml. of nitrogen-saturated potassium carbonate solution. The mixture is agitated for 30 minutes at room temperature, neutralized with 1.7 ml. of glacial acetic acid. diluted with water, and extracted with chloroform. After the extract has been worked up and concentrated by evaporation there is obtained 9a-fluorol-methylene-prednisolone, m.p. 24l243C. (from ethanol); [01],, +26.6 (dioxane).  
 e. Oxidation 2.5 g. of 9a-fluoro-l6-methylene-prednisolone- 2l-acetate is dissolved in ml. of pyridine and added to a mixture of 2.5 g. of chromium trioxide and 25 ml. of pyridine. After 12 hours. the reaction mixture is poured into 250 ml. of ethyl acetate and boiled for 5 minutes. The precipitate is vacuum-filtered and thoroughly washed with hot ethyl acetate. The filtrates are washed neutral with dilute sulfuric acid, dried, and concentrated by evaporation. The residue of crude 9afluorol 6-methylene-prednisone-2 l-acetate is obtained in the pure form by recrystallization from methanol; m.p. 242243C.; [(11 +lO3.8 (dioxane).  
  Analogously, by oxidizing 9a-fluoro-l6-methyleneprednisolone, there is obtained 9a-fluoro-l6-methylene-prednisone, m.p. 24l243C.; [a],, +86.l (dioxane).  
 f. Esterification One gram of 9a-fluoro-l6-methylene-prednisolone is dissolved in 10 ml. of pyridine and mixed with 10 ml. of tert.-butyl acetyl chloride. After allowing the reaction mixture to stand for 1 /2 hours at room temperature, the mixture is poured into 100 ml. of water, and the thus-precipitated 9a-fluoro- 1 6-methyleneprednisolone-Zl-tert.-butyl acetate is vacuum filtered, washed with water, dried, and recrystallized from acetone/ether; m.p. 23 l232C.; [01],, +20 (chloroform).  
  In an analogous manner, the following esters of 9afluorol 6-mcthylene-prednisolone are obtainable:  
 2l-chloroacetate, m.p. 232-234 C.; [a] +l 7 (dioxane);  
 2l-trimethylacetate, m.p. 234-235 C.;  
 2l-diethylaminoacetate, m.p. 2162l7C.; [04],,  
 +266 (dioxane);  
 Zl-enanthate, m.p. 231232C.; [041 +4.5 (chloroform).  
  The preceding example can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding example.  
  From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.  
  The techniques for conducting the reaction steps of the present process (microbiological dehydrogenation in the 1(2) position, formation of the 9oz-fluoro-1IB- hydroxy steroid from the 9,8,1 lB-epoxide, introduction of the 2l-acetoxy group) are well known in steroid chemistry. Reference is made to L. F. Fieser and M. Fieser, Steroids, Reinhold Publishing Corporation, New York, and Chapman &amp; Hall Ltd., London (1959), particularly to pages 686, 683 and 62-5 of this book, and to the literature cited therein. On the other hand, it was surprising and unexpected that such high yields would be obtained by the processes of this invention as compared to other processes apparently as the result of the use of starting materials which heretofore were not considered appropriate for the intended objectives.  
 What is claimed is:  
  1. In a process for the production of 9a-fluoro-l6- methylene-prednisolone-Zl-acetate, the improvement comprising the step of reacting 9a-fluoro-l6- methylene-l ,4-pregnadiene-l 1B, l7a-diol-3,20-dione with iodine in an alkaline solution, and thereafter with an alkali acetate.  
 LII