A convenient preparation of the side-chain lactone ring of a withanolide precursor.

Condensation of C22 and C21 steroidal aldehydes with ethyl 4,6-dimethyl-2-oxo-2H-pyran-5-carboxylate 1 in alkaline medium, followed by decarboxylation, provides a simple route to the alpha, beta-unsaturated side-chain delta-lactone synthesis for a classical withanolide precursor.