Fungal Steroids. A Stereoselective Synthesis of Isoantheridiol

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Abstract
The synthesis and characteristics of the 23-hydroxy-δ-lactone isomer of antheridiol and (22S,23R) 3β-hydroxy-24-carbethoxymethylene-cholest-5-en-22,23-epoxide are described. The synthesis of the latter compound follows from the highly stereoselective epoxidation of 3β-acetoxy-cholesta-5,22-diene-24-one followed by a Wittig reaction to give (22S,23R) 3β-acetoxy-24-carbethoxymethylene-cholest-5-en-22,23-epoxide which upon treatment with perchloric acid gave exclusively the δ-lactone. Hematoporphyrin-sensitized photooxygenation followed by cupric acetate oxidation gave the required α,β-unsaturated ketonic system in ring B. The 22R,23S stereochemical assignment of the final product is based on circular dichroism spectra.

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