β-stabilizing effect of silicon substituent at C-3 on a C-4 cation and a radical in the 2-azetidinone systems is studied using NMR kinetics. While the β-effect is virtually nonexistent in the case of a cation, a foiled β-effect (only a 3-fold rate enhancement) is observed for a radical intermediate. From both the experimental and theoretical studies, it is demonstrated that antiaromaticity is playing
Chemical asymmetric syntheses of the keyintermediates (4,6,8) for the synthesis of monobactam antibiotics (SQ 26776 (azthreonam), sulfazecin, and SQ 26180) are accomplished from (±)-4-phenylsulfonyl-2-azetidinone.