BROMINATION OF STEROID 20-KETALS

Abstract
Bromination of 3α,12α-diacetoxypregnan-20-one ethylene ketal provided in good yield the corresponding 21-monobromo compound. This product, on acid hydrolysis and subsequent acetolysis, gave the known 3α,12α,21-triacetoxypregnan-20-one. Acid hydrolysis of the bromoketal, followed by Faworsky rearrangement, led to 3α,12α-diacetoxy-17α-methyletiocholanic acid methyl ester.