A short synthesis of an important precursor to a new class of bicyclic β-lactamase inhibitors

A short synthesis of an important precursor to known bicyclic β-lactamase inhibitors is described. The synthesis uses commercially available trans-3-hydroxy-l-proline 1. Protection of the amino group followed by formation of the hydroxamate and cyclization using Mitsunobu conditions afforded bicyclic β-lactam 4 in three steps in 53% overall yield.