ChemInform Abstract: Synthesis and Antimicrobial Properties of New Cepham and Penam Derivatives with the Carboxylic Group in the 'Wrong' β-Configuration

The cepham (9) and the penam (10) derivatives, with their carboxylic group in the “wrong” β-configuration, which is opposite to that exhibited by the common penicillins, were synthesized and assayed in vitro for antimicrobial properties. Compounds 9 and 10 , tested on Gram-positive and Gram-negative bacteria, both sensitive and resistant to β-lactamase inactivation, exhibited a very poor activity, directed only against non-β-lactamase-producing Gram-positive bacteria. One of the possible explanations for these results may be found in unfavourable steric and electronic effects deriving from the α-oriented methoxy group which is adjacent to the pharmacophoric carboxylic function.