The diastereoselective synthesis of functionalised spirocyclic lactams and lactones using a Cope elimination/intramolecular nitrone cycloaddition strategy

Functionalised hydroxylamine derivatives of (S)-proline and pipecolic acid have been prepared using a Cope elimination. These hydroxylamines have been found to undergo oxidation to the nitrone either in the presence of air or a catalytic quantity of TPAP. An intramolecular 1,3-dipolar cycloaddition then occurs between the nitrone and pendant double bond to give tricyclic lactams and lactones with high diastereoselectivity.