Synthesis of 3α,7α-dihydroxy-5β-cholestan-26-oic acid from 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid: configuration in the bile of Alligator mississippiensis

Article abstract of DOI:10.1016/0039-128X(92)90002-Q

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 70percent 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 58percent 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 diastereoisomers in approximately 25percent 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.Keywords: 3α,7α-dihydroxy-5β-cholestan-26-oic acid; 3α,7α,12α-trihydroxy-5β-cholestan-26-oic acid; diastereoisomers; alligator bile; thin-layer chromatography; high-performance liquid chromatography; Alligator mississippiensis; steroids