Model Studies for Coenzyme B12 Dependent Enzyme-Catalyzed Rearrangements. Kinetics and Mechanism of Decomposition of Formylmethylcobalamin and Its Acetals

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32 Scopus citations

Abstract

Syntheses of formylmethylcobalamin and the kinetics and mechanism of decomposition of the aldehyde and its acetals are reported. Two different pathways were observed for the acid-catalyzed decomposition of the cobalamin acetals: direct cobalt-carbon bond cleavage to B12b and a vinyl ether, and normal acetal hydrolysis to formylmethylcobalamin, followed by a rate-determining fission of the cobalt-carbon bond to B12b and acetaldehyde. The rate law of decomposition of formylmethylcobalamin (A) is d[A]/dt = -K [A][H3O+]; the acid sensitivity and bimolecularity of the decomposition were rationalized as an initial protonation of the formyl carbonyl followed by a direct cleavage of the cobalt-carbon bond.

Original languageEnglish (US)
Pages (from-to)4633-4639
Number of pages7
JournalJournal of the American Chemical Society
Volume98
Issue number15
DOIs
StatePublished - Jul 1 1976

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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