Microbiological hydroxylation of steroids. Part VII. The pattern of dihydroxylation of mono-oxo-5α-androstanes and -5α-estranes with the fungus Rhizopus nigricans

Although steroidal monoketones with the carbonyl group in ring B or C are relatively unreactive towards Rhizopus nigricans, 2-, 3-, 16-, and 17-ketones give modest yields of dihydroxy-derivatives. The position of the carbonyl group influences the direction of the hydroxylation process: comparison of the 11,16-dihydroxylation of 3-ketones with the 3,7-dihydroxylation of 17-ketones suggests that a reversal effect is operating.16-Hydroxylation, not previously recorded with this fungus, occurs commonly with the present androstane and estrane derivatives, i.e. steroids lacking side-chains at position 17. Estr-4-en-3-one gives three 16-oxygenated products (total yield 68%), the main one being the 10β,16β-dihydroxy-Δ4-3-ketone.