Construction of a γ-Butyrolactone Moiety: A Facile Synthesis of 3β- Hydroxy-5,6-Dihydro-17β -Methoxy-Pregnan-21,16α-Carbalactone - a New D-Ring Fused Steroidal γ-Butyrolactone from an Abundant 20- Oxopregnane using Metal Mediated Halogenation as the Key Step

A new D-ring fused steroidal γ-butyrolactone, 3β-hydroxy-5,6-dihydro-17β-methoxypregnan- 21,16α-carbalactone from abundant 20-oxopregnane,5,6-dihydro pregnenolone acetate using the high yield metal mediated C-21 functionalization reaction with MnO2-TMSCl/AcCl-AcOH system as the key step has been described. Furthermore, the application of this reaction paving a way to synthesize 3β,21-diacetoxy -16α,17α-epoxy-pregnan-20-one - a potent precursor towards the synthesis of a series of D-ring fused steroidal γ-butyrolactones has also been illustrated. The work highlights a convenient approach in constructing a D-ring fused steroidal γ-butyrolactone system from abundant 20-oxosteroids which might have general applicability in non-steroidal cyclic system.