Epalons: Synthesis of 7-Norallopregnanolone
The title compound 2 was prepared from (20 R )-pregn-5-ene-3β,20-diyl 3-acetate 20-benzoate ( 3 ) via (20 R )-3β-acetoxy-20-benzoyloxy-5-oxo-5,6-secopregnan-6-oic acid ( 5 ) and (20 R )-3β-acetoxy-20-benzoyloxy-7-nor-5β,6α-pregnane-6,5-carbolactone ( 6 ). An intermediate 7-norpregn-5-ene derivative - (20 R )-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 (20 R )-7-nor-5α-pregnane-3β,20-diyl 3-tosylate 20-benzoate ( 12 ) and (20 R )-7-nor-5α-pregnane-3α,20-diyl 20-benzoate 3-formate ( 13 ).