O'Brien Colin, Poláková Monika, Pitt Nigel, Tosin Manuela, Murphy Paul V
Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland.
Chemistry. 2007;13(3):902-9. doi: 10.1002/chem.200601111.
The reaction of silylated nucleophiles with 6,1-anhydroglucopyranuronic acid (glucuronic acid 6,1-lactones) catalysed by tin(IV) chloride provides 1,2-trans or 1,2-cis (deoxy)glycosides in a manner dependent on the donor structure. The alpha-glycoside was obtained for reactions of the donor with the 2-acyl group and 2-deoxydonors, whereas the 2-deoxy-2-iodo donor gave the beta-glycoside. Experimental evidence shows that when 1,2-cis-glycoside formation occurs, the anomerisation of initially formed 1,2-trans-glycosides catalysed by SnCl(4) is possible. The anomerisation of beta-D-glucopyranosiduronic acids was found to be faster, in some cases, than anomerisation of related beta-D-glucopyranosiduronic acid esters and beta-D-glucopyranoside derivatives and the rates are dependent on the structure of the aglycon. Moreover, the rates of anomerisation of beta-D-glucopyranuronic acid derivatives can be qualitatively correlated with rates of hydrolysis of beta-D-glucopyranosiduronic acids. Mechanistic possibilities for the reactions are considered.
在四氯化锡催化下，甲硅烷基化亲核试剂与6,1-脱水吡喃葡萄糖醛酸（葡萄糖醛酸6,1-内酯）的反应，根据供体结构的不同，可生成1,2-反式或1,2-顺式（脱氧）糖苷。对于带有2-酰基的供体和2-脱氧供体的反应，可得到α-糖苷，而2-脱氧-2-碘代供体则生成β-糖苷。实验证据表明，当发生1,2-顺式糖苷形成时，由SnCl₄催化的最初形成的1,2-反式糖苷的异头化是可能的。已发现，在某些情况下，β-D-吡喃葡萄糖醛酸的异头化比相关的β-D-吡喃葡萄糖醛酸酯和β-D-吡喃葡萄糖苷衍生物的异头化更快，且反应速率取决于苷元的结构。此外，β-D-吡喃葡萄糖醛酸衍生物的异头化速率与β-D-吡喃葡萄糖醛酸的水解速率在定性上具有相关性。文中考虑了这些反应的可能机理。
