Alkyl transfer from quaternary ammonium salts to cobalt (I): Model for the cobalamin-dependent methionine synthase reaction

doi:10.1016/S0040-4020(01)85359-X

Tetrahedron

Volume 50, Issue 29, 1994, Pages 8863-8870

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Abstract

The reaction of cobaloxime(I) with diverse quaternary ammonium salts leads, in general, to a group transfer from nitrogen to cobalt. The behaviour of the salts in these transalkylations is consistent with an S_N2 mechanism, involving Co(I) as a nucleophile. In a model study of the cobalamin-dependent methionine synthase reaction, 5-¹³CH₃-methyl labelled 5,5,6,7-tetramethyl-5,6.7,8-tetrahydropteridinium salt(23) -a model of the natural coenzyme 5-CH₃H₄-folate (1)- was allowed to react with cobaloxime(I) and cobalamin(I). In each case the formation of the methyl transfer product, namely, methylcobaloxime and mothylcobalamin, respectively, was shown by ¹³C-NMR spectroscopy.

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References (14)

R.G. Matthews
G.N. Schrauzer et al.
J. Am. Chem. Soc
(1967)
H.P.L. Hogenkamp et al.
Biochemistry
(1985)
H.P.L. Hogenkamp et al.
Biochemistry
(1987)
R.G. Matthews et al.
Chem. Rev
(1990)
C. Bied-Charreton et al.
C.R. Acad. Sc. Paris, Ser. C
(1971)
G.N. Schrauzer et al.
J. Am. Chem. Soc
(1966)

There are more references available in the full text version of this article.

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Citation Excerpt :
There is a solid chemical basis for this mechanism. Quaternary amines, with a full positive charge on nitrogen, do not require activation, as shown by studies of methyl transfer from a variety of quaternary ammonium salts to Co(I)‐cobaloxime (Hilhorst et al., 1994), trimethylphenylammonium cation to cob(I)alamin (Pratt et al., 1994), and dimethylaniline at low pH to Co(I)‐cobyrinate (Zheng et al., 1999). In addition, methyl transfer is catalyzed by Lewis acids, such as Zn(II) (Wedemeyer‐Exl et al., 1999).
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Alkyl transfer from quaternary ammonium salts to cobalt (I): Model for the cobalamin-dependent methionine synthase reaction

Abstract

J. Am. Chem. Soc

Biochemistry

Biochemistry

Chem. Rev

C.R. Acad. Sc. Paris, Ser. C

J. Am. Chem. Soc