Open AccessStereochemistry of the Enzymatic Conversion of a Δ 4 ‐3‐Oxosteroid into a 3‐Oxo‐5β‐Steroid
Author(s) -
Björkhem I.
Publication year - 1969
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1969.tb19625.x
Subject(s) - cholic acid , dehydrogenation , chemistry , tritium , steroid , bile acid , chenodeoxycholic acid , enzyme , stereochemistry , medicinal chemistry , organic chemistry , biochemistry , catalysis , hormone , physics , nuclear physics
The synthesis of [4‐ 3 H,4‐ 14 C]7α‐hydroxycholest‐4‐en‐3‐one is described. The transformation of this compound into cholic acid in the bile fistula rat occurred with retention of the tritium label. The position of the tritium label in the isolated cholic acid was established by oxidation at the C‐3 position of the methylated derivative followed by dehydrogenation with selenium dioxide yielding methyl 7α,12α‐dihydroxy‐3‐oxo‐chol‐4‐enoate. This compound retained most of the tritium label. Since selenium dioxide dehydrogenation of a 3‐oxo‐5β‐steroid could be shown to involve a preferential loss of a 4α‐hydrogen, it was concluded that the tritium label in the cholic acid isolated from bile was located in the 4β‐position. The enzymatic reduction of the Δ 4 double bond in 7α‐hydroxycholest‐4‐en‐3‐one in its conversion into cholic acid thus involves a trans diaxial addition of hydrogens.