K. C. Wang

Microbial transformation of 3-hydroxy-5,6-cyclopropanocholestanes--an alternative route to 6-methylsteroids.

Incubation of 3beta-hydroxy-5,6alpha-cyclopropano-5alpha-cholestane (4), 3beta-hydroxy-5,6beta-cyclopropano-5beta-cholestane (5), and 3beta-hydroxy-5,6alpha-cyclopropano-5alpha-cholest-7-e ne (6) with Mycobacterium sp. (NRRL B-3805) gave a mixture of side chain cleaved 17-keto steroids as the major products in 52, 57, and 69% yields, respectively. Among these 17-keto steroids, the cyclopropyl ring eliminated product, androst-4-ene-3,17-dione (9), was isolated in 6, 4, and 8% yields, respectively. A cyclopropyl ring migration product, 6alpha,7alpha-cyclopropanoandrost-4-ene-3,17-dione (16), was isolated from the incubation mixture of 6 in 4% yield, also 10% yield of 16 was obtained when 5, 6alpha-cyclopropano-5alpha-androst-7-ene-3,17-dione (12) was incubated. The cyclopropyl ring opening and subsequent reduction followed by oxidation of the two major biotransformation products, 5, 6beta-cyclopropano-5beta-androsta-3,17-dione (10) and 5, 6alpha-cyclopropano-5alpha-androsta-3,17-dione (7), gave 6beta- and 6alpha-methylandrost-4-ene-3,17-dione in 60, and 45% yields, respectively.

Synthesis of steroid intermediates via alkylation of dianion derived from acetoacetic ester

A synthetic route for A-ring aromatic steroid intermediates starting from alkylation of dianion derived from acetoacetic ester with m-methoxyphenylethyl bromide to form benzene ring connected to a linear six-carbon fragment is described. This unit, after chemical modifications to 5, was condensed with 2-methylcyclopentan-1,3-dione (6a) to form prochiral trione, 7a, a key synthetic intermediate in A-ring aromatic steroid. Microbial reduction of 7a with Schizosaccharomyces pombe (NRRL Y-164) gave chiral (-)-11 in 65% yield. Starting from 2,2-dimethylsuccinic acid, 2,4,4-trimethylcyclopentan-1,3-dione (6a) was prepared, which was condensed subsequently with 5 to form racemic 7b trione intermediate. Asymmetric cyclization of 7b in the presence of L-(-)-phenylanlanine, followed by acidic cyclization led to regiospecific synthesis of 16,16-dimethyl tetracyclic steroid intermediate.

Microbial reduction of 2-(6-m-methoxyphenyl-3-oxohexyl)-2,4,5-trimethylcyclopenta-1,3-dione with Schizosaccharomyces pombe (NRRL Y-164)

A mixture of cis- and trans-2-(6-m-methoxyphenyl-3-oxohexyl)-2,4-dimethylcyclopenta-1,3-dione (±)-10 was synthesized and incubated with Schizosaccharomyces pombe (NRRL Y-164) to give (+)-11, (+)-12, (−)-13, and (−)-14 in 19, 13, 22, and 16% yields, respectively. Chromic acid oxidation of these microbiologically reduced products gave (−)-10a, (+)-10b, (+)-10a, and (−)-10b, respectively.