Cyclization of N -Boc-( E )-α,β-unsaturated γ-amino acid active esters into N -Boc-( Z )-α,β-unsaturated γ-lactams through E → Z isomerization

Here, we are reporting the spontaneous transformation of the active esters of -Boc protected -α,β-unsaturated γ-amino acids into the corresponding -α,β-unsaturated γ-lactams with concomitant → isomerization in the presence of a weak base. No cyclization was observed in the absence of the base. Analysis revealed that amide γ-NH is crucial for both lactamization and → isomerization. This mild transformation provides easy access to the synthetically challenging α,β-unsaturated γ-lactams and also gives new insights into the → isomerization of double bonds.