The use of chiral bicyclic lactams, in their thiocarbonyl form 9, has been shown to serve as important intermediates for producing α-quaternary alkyl derivatives 8, which were readily transformed into the title compound (-)-1. The reversibility of the thio-Claisen rearrangement, 15⇌ 8, was clearly demonstrated and appears to be unprecedented. Solvent effects to alter the equilibrium position were studied and found to have only a moderate, but beneficial ...
