Stereochemistry of conjugate addition to 4- and 5-substituted α,β-unsaturated δ-lactones

Abstract

Conjugate addition, especially of the phenyldimethylsilylcuprate reagent, to 4- and 5-substituted α,β-unsaturated δ-lactones [(5) and (18)] is highly selective for the formation of the trans-products [(6), (7), (9), (10), and (19)], the silicon-containing products having ¹H n.m.r. coupling constants indicative of distortions from the chair conformation; the silyl group can be converted into a hydroxy group to give the lactones (8) and (20).