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.