Add time:07/21/2019         Source:sciencedirect.com

Synthesis of 25R- and 25S-diastereoisomers of 3α,7α-dihydroxy-5β-cholestan-26-oic acid from 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid is described. The 25S-diastereoisomer of 3α,7α, 12α-trihydroxy-5β-cholestan-26-oic acid was obtained by vigorous hydrolysis of the bile of Alligator mississippiensis followed by repeated crystallization of the hydrolysate, and the 25R-diastereoisomer was isolated by hydrolysis of the bile salts in bile of A mississippiensis with rat feces. Acetylation of the 25R- or 25S-diastereoisomer of methyl 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid under controlled conditions yielded the corresponding 3α,7α-diacetate in approximately 70% yield. The diacetate was quantitatively oxidized to methyl 3α,7α-diacetoxy-12-oxo-5β-cholestan-26-oate, which was converted into the 12-tosylhydrazone in approximately 58% yield. Reduction of the tosylhydrazone with sodium borohydride in acetic acid yielded the 25R- or the 25S-diastereoisomer of 3α, 7α-dihydroxy-5β-cholestan-26-oic acid as the major product. Purification via column chromatography yielded the pure diastereo-isomers in approximately 25% overall yield. The two diastereoisomers were resolved on thin-layer chromatography and high-performance liquid chromatography. When the bile of A mississippiensis was hydrolyzed with rat fecal bacteria, the 3α,7α-dihydroxy-5β-cholestan-26-oic acid isolated via Chromatographic purification was shown to be the 25R-diastereoisomer.

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