Synthesis of Pyrrolidine‐fused β‐lactams as Potential β‐lactamase Inhibitors

A synthetic protocol for the preparation of novel 3,4‐pyrrolidine‐fused β‐lactams was developed. The proposed 2,6‐diazabicyclo[3.2.0]heptan‐7‐one scaffolds were constructed through an amido group‐induced, potassium tert‐butoxide‐promoted intramolecular ring closure of 3‐acylamino‐4‐oxiranyl‐β‐lactams as the key reaction step. Alternatively, the desired cyclization was also effected by means of a scandium triflate‐mediated catalytic approach. In this way, a set of stereodefined 3,4‐pyrrolidine‐fused β‐lactams was synthesized, which were preliminary evaluated as β‐lactamase inhibitors. These first‐line biological assessments led to the identification of a 2‐benzoyl‐6‐(4‐methoxyphenyl)‐substituted diazabicyclo structure as an eligible starting point for further β‐lactamase inhibitor optimization studies.