Substituted-Amidine Functionalized Monocyclic β-Lactams: Synthesis and In Vitro Antibacterial Profile

Scheme 4

Synthesis of compounds 18a,b and 18d–f. Reagents and conditions: (a) 15, EtOH-CHCl₃, rt, 26–60%; (b) 12a, HOBT, DCC, NaHCO₃, DMF, 0°C – rt, 41–84%; (c) TFA, CH₂Cl₂, 0°C – rt, 12–29%.