Nitrone [2+3]-cycloadditions in stereocontrolled synthesis of a potent proteasome inhibitor: (-)-omuralide.

A new stereocontrolled synthetic route to omuralide has been developed from methyl pyroglutamate. This route involves regio- and stereoselective N-methylnitrone 1,3-dipolar cycloadditions to appropriate pyrrolinones, beta-eliminations, and highly selective hydrogenations as the main steps.