61365-37-5Relevant academic research and scientific papers
The Chemical Reactivity of Penicillins and Other β-Lactam Antibiotics
Proctor, Philip,Gensmantel, Nigel P.,Page, Michael I.
, p. 1185 - 1192 (2007/10/02)
The rates of the acid catalysed hydrolysis of penicillins and cephalosporins are linear in Ho and, unlike other amides, show no rate maximum with increasing acidity.Electron-withdrawing substituents at C-6 in penicillins decrease the rate of hydrolysis with a ρI of ca. 4 and they decrease the rate when attached to the amine leaving group.The acylamido-group at C-6 in penicillins, but not at C-7 in cephalosporins, exhibits neighbouring group participation with a rate enhancement of ca. 103.The absence of penicillenic acid formation from benzylpenicillin in acidic solution is not due to the ionisation of the carboxy-group.These observations are rationalised by a scheme involving N-protonation and formation of an acylium ion intermediate.The alkaline hydrolysis of penicillins proceeds 102 faster than a β-lactam after correction for substituent effects.There is no evidence for substantial inhibition of amide resonance in the bicyclic β-lactam antibiotics, little evidence to indicate extra strain in these systems and no evidence that expulsion of the leaving group at C-3 in cephalosporins occurs in the transition state.
