Lewis Acid-Promoted Intermolecular Carbonyl-ene Reaction of Enantiopure 4-Oxoazetidine-2-carbaldehydes. Rapid Entry to Novel Fused Polycyclic β-Lactams
Lewisacid-promoted carbonyl-ene reaction of enantiomerically pure 4-oxoazetidine-2-carbaldehydes with various activated alkenes gives 4-[(1'-hydroxy)homoallyl]-beta-lactams with a very high level of syn diastereofacial selectivity. The above homoallylic alcohols are used for the diastereoselective preparation of fused bicyclic, tricyclic, and tetracyclic beta-lactams of nonconventional structure using