A novel and stereocontrolled synthesis of (5R)-(Z)-6-(1-methyl-1,2,3-triazol-4-ylmethylene)penem-3-carboxylic acid, a potent broad spectrum β-lactamase inhibitor

Abstract

The key step in the preparation of the title compound (BRL 42715) from 6-aminopenicillanic acid was the condensation of the anion, generated by deprotonation of p-methoxybenzyl (5R,6S)-6-bromopenem-3-carboxylate(10), with 1-methyl-1,2,3-triazole-4-carbaldehyde; in situ acylation, followed by reductive elimination afforded the isomeric (Z)- and (E)-6-triazolylmethylene penem esters, (12) and (13) respectively.