134767-09-2Relevant articles and documents
An Esterase with β-Lactamase Activity
Jones, Mark,Page, Michael I.
, p. 316 - 317 (1991)
Porcine liver esterase selectively catalyses the hydrolysis of the β-lactam of the methyl ester of benzylpenicillin with a kcat/Km of 675 dm3 mol-1 s-1 and without hydrolysing the methyl ester function.
The Effect of Increasing the Hydrophobicity of Penicillin on its Micelle-catalysed Hydrolysis
Gensmantel, Nigel P.,Page, Michael I.
, p. 155 - 160 (2007/10/02)
Micelles of cetyltrimethylammonium bromide catalyse the alkaline hydrolysis of alkylpenicillins and benzylpenicillin methyl ester.The equilibrium constant for binding the alkylpenicillin to the micelle and the rate constants have been obtained.Binding increases with increasing alkyl chain length but shows a non-linear dependence upon the Hansch ?-value and the rate reaches a maximum value with heptylpenicillin.The free energy of transfer of a methylene group from water to the micelle shows a maximum value of 0.71 kcal mol-1.The negative charge of the carboxylate group of penicillin is not necessary for catalysis.
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.
