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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 12, Number 6
BKCSDE 12(6)
June 20, 1991 

 
Title
Theoretical Studies on the Methanolysis of a Cephalosporin; Mimicking Acylation of the Active Site Serine of D-Ala-D-Ala Transpeptidases
Author
Keepyung Nahm
Keywords
Abstract
Methanolysis of a β-lactam ring of a cephalosporin was simulated with AM1 semiempirical quantum mechanical calculation. The tetrahedral intermediate TD1 from an O-protonated cephalosporin and a methanol transfers the proton intramolecularly to the C-4 carboxylate to generate an oxyanion, i.e., second tetrahedral intermediate TD2, which undergoes the amide bond cleavage without further protonation on the N-5. For this cleavage a low-energy barrier TS2 was located. According to the energy diagram, tetrahedral intermediates easily undergo ring cleavage even without the protonation on the amide nitrogen.
Page
674 - 678
Full Text
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