Epalons: Synthesis of 7-Norallopregnanolone

Abstract

The title compound 2 was prepared from (20R)-pregn-5-ene-3β,20-diyl 3-acetate 20-benzoate (3) via (20R)-3β-acetoxy-20-benzoyloxy-5-oxo-5,6-secopregnan-6-oic acid (5) and (20R)-3β-acetoxy-20-benzoyloxy-7-nor-5β,6α-pregnane-6,5-carbolactone (6). An intermediate 7-norpregn-5-ene derivative - (20R)-7-norpregn-5-ene-3β,20-diyl 3-acetate 20-benzoate (7) - was hydrogenated using diimide in statu nascendi. The inversion of configuration at carbon C-3 was carried out via (20R)-7-nor-5α-pregnane-3β,20-diyl 3-tosylate 20-benzoate (12) and (20R)-7-nor-5α-pregnane-3α,20-diyl 20-benzoate 3-formate (13).