Studies on Conformation and Reactivity. X. The Synthesis and Transannular Cyclization of 17β-Benzoyloxy-2α-hydroxy-5β-androstane leading to 17β-Benzoyloxy-2α, 9α-epoxy-5β-androstane

17β-Benzoyloxy-2α-hydroxy-5β-androstane (XIb), the key intermediate for the transannular cyclization reaction from 2C to 9C in the 5β-androstane system, was synthesized from testosterone (III) in six steps and in the overall yield of 17.6% via the intermediacy of 2α-hydroxy-4-en-3-oxo system (VII). The stereochemistry of the epoxidation of the 4-en-3-oao system (III) with alkaline hydrogen peroxide was established, the reaction favoring the formation of the 4β, 5-epoxide (IVb) to the formation of the 4α, 5-isomer (IVa) in the relative ratio of 5:1. Meanwhile, oxidation of XIb with Jones reagent afforded the 2-oxo-5β system (XIIIb) which exhibits negative Cotton effect curves with much weaker intensity compared with that of positive Cotton effect curves exhibited by the 2-oxo-5α system (XIIIa).Treatment of XIb with lead tetraacetate in benzene afforded 17β-benzoyloxy-2α, 9α-epoxy-5β-androstane (XVII). The 17β-acetoxy analogue (XIX) of the 2α, 9α-epoxide (XVII) was converted to the 9α, 11α-epoxide system (XXII) via the 9 (11)-eno intermediate (XXI). Reductive cleavage of XXII with lithium-ethylamine afforded the 2α, 9α, -17β-trihydroxy-5β-androstane (XXIII) which gave 2α, 17β-diacetate (XXIV).