Stereoselective Synthesis of fused g-lactams by intramolecular nitrone cycloaddition

A series of nitrones 5 joined by amides to olefines were prepared in situ from the related aldehydes with N-methylhydroxylamine. The nitrone added intramolecularly to the olefin, and the cycloadditions gave fused γ-lactams 6 stereoselectively. A stereocentre located in positron α to the nitronic functionality 13 completely controls the stereochemical course of the intramolecular cycloaddition, which exclusively affords compound 14 with simultaneous introduction of four stereocentres. The formation of this latter compound was also supported by PM3 calculations. Furthermore, simple heating of unsaturated oxine 17 led to compound 19 via intramolecular oxime olefin cycloaddition