title: Substituent effects in cephalosporins as assessed by molecular orbital calculations, nuclear magnetic resonance, and kinetics.
abstract: For cephalosporins with different side chains at position 3, the quantum mechanically computed charge distribution in the beta-lactam carbonyl group can be correlated with observables, such as carbon-13 chemical-shift differences at C3 and C4 of the dihydrothiazine ring and alkaline rates of hydrolysis of the beta-lactam. The relationship of these properties and the theoretical transition-state energy (TSE) corroborate the fact that chemical reactivity is one important determinant affecting inhibitory activity of cephalosporins against peptidoglycan-regulating enzymes.
mesh_terms: D002511:Cephalosporins; D055598:Chemical Phenomena; D002621:Chemistry; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013329:Structure-Activity Relationship
chemical_list: D002511:Cephalosporins