The Mechanism of the Microbial Hydroxylation of Steroids. Part 2. Hydroxylation of a Δ4-3-Ketosteroid Analog by Rhizopus arrhizus ATCC 11145

Abstract

The Δ4-3-ketosteroid analog (± )-4a-methyl-4,4a,5,6,7,8-hexahydro-2(3H) naphthalenone (1) is hydroxylated at both C-8α and C-8β by Rhizopusarrhizus ATCC 11145. The ratio of C-8α to C-8β hydroxylation is compared with that obtained from the peracid oxidation of 2-ethoxy-4a-methyl-3,4,4a,5,6,7-hexahydronaphthalene (4) and a mechanism is proposed for both microbial and chemical hydroxylation in which the stereochemistry of the product is transition state controlled. The significance of this to the mechanism of microbial C-6β hydroxylation of Δ4-3-ketosteroids is discussed.