| Summary: | 博士 === 國立臺灣大學 === 藥學研究所 === 87 === This thesis contains two parts, which are (I) Microbial Transformation of Steroid Synthetic Intermediates and (II) Microbial Transformation of Sterol Analogues
(I) Microbial Transformation of Steroid Synthetic Intermediates
The racemic 2-(6-m-methoxyphenyl-3-oxohexyl)-2,4,4-trimethylcyclopenta-1,3-dione (66) and 2-(6-m-methoxyphenyl-3-oxohexyl)-2,4-dimethylcyclopenta-1,3-dione (67) were synthesized and subjected to microbial reduction with Schizosaccharomyces pombe (NRRL Y-164), respectively. From the incubation mixture of 66, (-)-68, (+)-69, and (+)-70 were isolated in 37, 12, and 19% yields, respectively. Chromic acid oxidation of (-)-68 gave (+)-66 while oxidation of (+)-69, and (+)-70 gave (-)-66, respectively. Sodium borohydride reduction of (+)-66 followed by Oppenauer oxidation yielded (-)-68 and (-)-70, and the same treatment of (-)-66 yielded (+)-68 and (+)-70, respectively. From the incubation mixture of 67, (+)-72a, (+)-72b, (-)-73a and (-)-73b were isolated in 19, 13, 22, and 16% yields, respectively. Chromic acid oxidation of (+)-72a gave (-)-67a while oxidation of (-)-73a gave (+)-67a, and the same treatment of (+)-72b and (-)-73b gave (+)-67b and (-)-67b, respectively. These results indicated that successful resolution of 66 and 67 were accomplished. These results showed that the presence of methyl substitution on cyclopentane ring influenced the course of microbial reduction.
(II) Microbial Transformation of Sterol Analogues
In order to investigate whether the cyclopropyl ring opening capability of Mycobacterium sp. (NRRL B-3805), would be applicable to 5,6-cyclopropanosterols, 3b-hydroxy-5,6a-
cyclopropano-5a-cholestane (74), 3b-hydroxy-5,6b-
cyclopropano-5b-cholestane (75) and 3b-hydroxy-5,6a-
cyclopropano-5a-cholest-7-ene (76) were prepared and incubated. From the incubation of these three 3b-hydroxy-5,6-cyclopropano- cholestanes, the cyclopropyl ring eliminated product, androst-4-en-3,17-dione (79) was obtained in 6, 4, and 8% yields, respectively. In addition, we obtained the 5,6-cyclopropyl ring transformed to 6,7-cyclopropyl ring product, 6,7a-cyclopropano-6a-androst-4-ene-3,17-dione (84) from 76. The side-chain cleaved 5,6-cyclopropyl 17-ketosteroids were isolated as the major product in all cases : 77 (43%) and 78 (3.6%) from74; 80 (38%) and 81 (15%) from 75; 82 (11%), 83 (50%), 85 (2-4%) and 86 (1-2%) from 76. These study showed that the cyclopropyl ring located on the 5, 6-position of steroid molecule could be eliminated in some extent by this microorganism.
The lanosta-7,9(11)-diene-3b-ol (90) was prepared and incubated, which led to the isolation of two C19 steroids as the major metabolites, 93 (30%) and 94 (7.1%), methyl 12a-hydroxybisnorchola-4,17(20)-dien-22-oate (91) was also isolated in low yield (0.7%). These results indicate that this microorganism is capable of carrying out saturation of the C=C bond, methylating the carboxylic function, and 12a-hydroxylation in the steroid nucleus.
In an effort to learn more about the enzymatic capabilites of Mycobacterium sp. (NRRL B-3805) in regard to sterol transformation, dihydrosarsasapogenin (97) was prepared and incubated, which led to the isolation of five products in 98 (0.5%), 99 (6.6%), 100 (5%), 101 (16%) and 102 (4.5%) yields, respectively, while 15 % of 97 was recovered. Among these products, 102 was a C19 steroid. Isolation of C19 steroid indicated that this microorganism is capable of cleaving the ether linkage between C-16 and C-22 in 97. In addition, l2a-hydroxylation was also observed in this study.
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