Diastereoselective Synthesis of γ- and δ‑Lactams from Imines and Sulfone-Substituted Anhydrides

Sulfone-substituted
γ- and δ-lactams have been prepared
in a single step with high diastereoselectivity. Sulfonylglutaric
anhydrides produce intermediates that readily decarboxylate to provide
δ-lactams with high diastereoselectivity. Substituents at the
3- or 4-position of the glutaric anhydride induce high levels of stereocontrol.
Sulfonylsuccinic anhydrides produce intermediate carboxylic acids
that can be trapped as methyl esters or allowed to decarboxylate under
mild conditions. This method has been applied to a short synthesis
of the pyrrolizidine alkaloid (±)-isoretronecanol.