Microbiological hydroxylation of steroids. Part VIII. The pattern of monohydroxylation of diketones and keto-alcohols derived from 5α-androstane with cultures of the fungus, Rhizopus nigricans

Abstract

Diketones and keto-alcohols derived from 5α-androstane are readily converted into monohydroxy-derivatives by Rhizopus nigricans. Varying the positions and oxidation levels of the oxygen functions leads to hydroxylation at different positions. Substrates with one oxygen substituent in each of the terminal rings are attacked at position 11 or 7; those with one group in rings B or C are hydroxylated at position 16 if the second group is in ring A, and at position 3 if the second group is in ring D. The results are rationalised by assuming the presence of three dual-purpose sites on the enzyme surface capable of binding to the steroidal oxygen groups and of hydroxylating those positions of the steroid nucleus which come into their vicinity.