title: Structural and biosynthetic studies of a principal bile alcohol, 27-nor-5beta-cholestane-3alpha,7alpha,12alpha,24,25-pentol, in human urine.
abstract: The stereochemistry at C-24 and C-25 of 27-nor-5beta-cholestane-3alpha,7alpha,12alpha,24 ,25-pentol, a principal bile alcohol in human urine, and its biosynthesis are studied. Four stereoisomers of the C(26)-24,25-pentols were synthesized by reduction with LiAlH(4) of the corresponding epoxides prepared from (24S)- or (24R)-27-nor-5beta-cholest-25-ene-3alpha, 7alpha,12alpha,24-tetrol. The stereochemistries at C-25 were deduced by comparison of the C(26)-24,25-pentols with the oxidation products of (24Z)-27-nor-5beta-cholest-24-ene-3alpha,7alpha, 12alpha-triol with osmium tetraoxide. On the basis of this assignment, the principal bile alcohol excreted into human and rat urine was determined to be (24S,25R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha,24,25-pentol, accompanied by a lesser amount of (24R, 25R)-isomer. To elucidate the biosynthesis of the C(26)-24,25-pentol, a putative intermediate, 3alpha,7alpha, 12alpha-trihydroxy-27-nor-5beta-cholestan-24-one, derived from 3alpha,7alpha, 12alpha-trihydroxy-24-oxo-5beta-cholestanoic acid by decarboxylation during the side-chain oxidation of 3alpha,7alpha, 12alpha-trihydroxy-5beta-cholestanoic acid, was incubated with rat liver homogenates. The 24-oxo-bile alcohol could be efficiently reduced to yield mainly (24R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha,24-tetrol. If a 25R-hydroxylation of the latter steroid occurs, it should lead to formation of (24S,25R)-C(26)-24,25-pentol. Now it has appeared that a major bile alcohol excreted into human urine is (24S,25R)-27-nor-5beta-cholestane-3alpha,7alpha, 12alpha, 24, 25-pentol, which might be derived from 3alpha,7alpha, 12alpha-trihydroxy-27-nor-5beta-cholestan-24-one via (24R)-27-nor-5beta-cholestane-3alpha, 7alpha,12alpha,24-tetrol.
authors.affiliation: Institute of Pharmaceutical Sciences, Hiroshima University School of Medicine, Minami-ku, Hiroshima, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Une
authors.forename: S
authors.initials: S
authors.lastname: Takenaka
authors.forename: T
authors.initials: T
authors.lastname: Kuramoto
authors.forename: K
authors.initials: K
authors.lastname: Fujimura
authors.forename: T
authors.initials: T
authors.lastname: Hoshita
authors.forename: K
authors.initials: K
authors.lastname: Kihira
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D002777:Cholestanols / Q000138:chemical synthesis / Q000737:chemistry* / Q000652:urine*; D019826:Cholic Acid / Q000737:chemistry; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D006801:Humans; D008099:Liver / Q000737:chemistry; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012015:Reference Standards; D013237:Stereoisomerism
chemical_list: D002247:Carbon Isotopes; D002777:Cholestanols; C030249:27-norcholestane-3,7,12,24,25-pentol; D019826:Cholic Acid