Variable-Sized bis(4-spiro-fused-β-lactam)-Based Unsaturated Macrocycles: Synthesis and Characterization

The synthesis with structural identifications including NMR and HRMS spectral data along with single-crystal X-ray diffraction analysis (for 20b, 23b, 25b–27b) of a family of 14 new syn/anti bis-4-spiro-β-lactam-based unsaturated macrocycles (19a,b–27a,b), obtained by multistep synthesis including (i) diimine formation, (ii) Staudinger [2 + 2] ketene–imine cycloaddition, and (iii) ring-closing metathesis (RCM), is reported.