Diastereoselection in 1,3-dipolar cycloadditions of a chiral cyclic nitrone to α,β-unsaturated δ-lactones

1,3-Dipolar cycloadditions of the nitrone 1 to α,β-unsaturated δ-lactones: non-chiral 13, racemic mixture 3/4, d-glycero3, and l-glycero4 proceed with high stereoselectivity in the cases of 13 and 3 and a significant kinetic resolution in the case of the racemate 3/4. The exo approach to the re–re sides of the lactones predominates.