Ultrasound was found to promote the reaction between ethyl bromoacetate, zinc, and a Schiff base such that an excellent yield of P-lactams was obtained in a few hours at room temperature. ... Most p-lactam antibiotics found in nature are characterized by an a-aniido or an a-methanol side chain. Clavulanic acid (1) and related antibiotics' constitute so far the only p-lactam family that carries no substituent on the carbon adjacent to the p-lactam ...
[Palomo, Claudio; Cossio, Fernando P.; Arrieta, Ana; Odriozola, Jose M.; Oiarbide, Mikel; Ontoria, Jesus M. Journal of Organic Chemistry, 1989 , vol. 54, # 24 p. 5736 - 5745]