Mechanism of methylation of nucleoside sugar hydroxyl groups by diazomethane in the presence of stannous chloride
1981; Elsevier BV; Volume: 91; Issue: 1 Linguagem: Inglês
10.1016/s0008-6215(00)80988-x
ISSN1873-426X
AutoresLech Dudycz, A. Kotlicki, David Shugar,
Tópico(s)Carbohydrate Chemistry and Synthesis
ResumoAbstract Diazomethane rapidly reacts with SnCl 2 in methanol to give MeCl and Sn(OMe) 2 , both of which were isolated and identified. This reaction is the initial step in the apparent SnCl 2 - 2H 2 O-catalysed methylation of nucleosides by diazomethane. The actual catalyst, Sn(OMe) 2 , readily reacts with Bronsted acids, with exchange of ligands. For ribofuranosyl nucleosides, Sn 2+ binds to site(s) having a labile proton, the effect being particularly predominant with 5- and 6-membered cyclic structures, with the tin ion co-ordinated to the ionised hydroxyl groups of the sugar moiety. These cyclic structures account for the high reactivity of the hydroxyl groups towards Me + , as in the complexes of ribofuranosyl nucleosides with Bu 2 SnO. A similar, if not identical, mechanism operates in the case of glucopyranosides.
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