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

Scheme 1

Synthesis of compounds 9a–f. Reagents and conditions: (a) methyl (R)-oxirane-2-carboxylate, (salen)Co(III) complex, 4 Å molecular sieves, MTBE, rt, 81%; (b) H₂ (gas), dry MeOH, 0°C – rt, 82%; (c) triethylamine, H₂N-R_a-f, MeOH, 0°C –rt, 57–95%; (d) NaOH, THF-water, 0°C, 75–99%; (e) Ph₂CN₂, CH₂Cl₂, rt, 31–84%; (f) PhthN-OH, DEAD, PPh₃, THF, rt, 33–66%; (g) NH₂NH₂^.H₂O, EtOH, rt, quantitative.