Oxidation of Cyclic Hemiacetals into Diketones: Final Steps in the Conversion of a Triterpenoid Ring a into a Steroidal Enone by a New Short Route

Abstract

As a part of our studies in the conversion of triterpenoids into steroids we have reported¹ that the Jones oxidation of some triterpenoid hemiacetals (1) gives acyloxy acids (2) instead of the desired 1,5-diketones (3). We now report² the shortest route yet for the reconstruction of a triterpenoid ring A ketone (4) into a steroidal enone (7) involving as key steps the exhaustive Baeyer-Villiger oxidation³ of triterpenoid ketones (4) into δ-lactones (5) and mild chromium(VI) oxidation of cyclic hemiacetals (1) into diketones (3).