Reaction of (20S)-3β-Acetoxybisnorchol-5-enic Acid with Lead Tetraacetate ; : Structure of Pregnane Derivatives and a Dimer

Abstract

Reaction of 3β-acetoxybisnorchol-5-enic acid (1) with lead tetraacetate in benzene gave ⊿²0 and ⊿^{17 (20)} compounds (2a and 2b) and 20α-and 20β-acetoxy compounds (3a and 3b), with a trace of 20-keto compound (4) and a dimer (5). The structure of 5 was determined as 3'β-acetoxypregn-5'-en-20'α-yl 3β-acetoxybisnorchol-5-enate (Chart 1). The use of toluene or xylene in place of benzene resulted in decreased formation of 2b with the formation of the 17-ethyl compound (2c). The reactions were examined under various conditions (Table I) and the reaction mechanisms are discussed.