Synthesis of α- and β-d-(1→6)-C-Disaccharides by Wittig Olefination of Formyl C-Glycosides with Glycopyranose 6-Phosphoranes
摘要:
The synthesis of (1-->6)-C-disaccharides by Wittig condensation of formyl C-glycofuranosides and pyranosides with galacto-and glucopyranose B-phosphoranes is described herein. The method involves the coupling of the sugar aldehydes with the ylides and the reduction of the double bond of the resulting sugar alkenes, in most of the cases by catalytic hydrogenation. The reduction with nickel boride or diimide is employed in some special cases. O-Benzyl protective groups are removed by catalytic hydrogenation either in the course of the reduction of the double bond or in a subsequent step, while O-isopropylidene groups are cleaved by treatment with Amberlite IR-120. In this way, eight free beta-D-(1-->6)-C-disaccharides have been prepared in 26-61% overall yield starting from B-linked formyl C-glycosides. These include C-linked analogues of the biologically active disaccharides allolactose (Gal beta 1,6Glc), gentiobiose (Glc beta 1,6Glc), and N-acetylamino disaccharides (GalNHAc beta,6Gal and GalNHAc beta 1,6Glc). Moreover, the synthesis of two alpha-D-(1-->6)-C-disaccharides is described from formyl C-furanosides. The limiting condition of the synthesis of these stereoisomers is the configurational instability of the alpha-linked formyl C-glycosides under the basic conditions of the Wittig olefination.
Selectivity in the SmI2-induced deoxygenation of thiazolylketoses for formyl C-glycoside synthesis and revised structure of C-ribofuranosides
作者:Alessandro Dondoni、Paolo Formaglio、Alberto Marra、Alessandro Massi
DOI:10.1016/s0040-4020(01)00736-0
日期:2001.9
Deoxygenation of thiazolylketose acetates using SmI2–(CH2OH)2 or TMSOTf–Et3SiH affords thiazolyl C-glycosides with opposite α/β ratios. Examination of the thiazolyl α- and β-C-ribofuranoside pair by NOE experiments reveals that the earlier configuration assigned to one of these isomers has to be revised. Having prepared authentic anomeric α- and β-ribofuranose aldehydes from the corresponding thiazolyl
Synthesis of α- and β-<scp>d</scp>-(1→6)-<i>C</i>-Disaccharides by Wittig Olefination of Formyl <i>C</i>-Glycosides with Glycopyranose 6-Phosphoranes
作者:Alessandro Dondoni、Helene M. Zuurmond、Alessia Boscarato
DOI:10.1021/jo971177n
日期:1997.11.1
The synthesis of (1-->6)-C-disaccharides by Wittig condensation of formyl C-glycofuranosides and pyranosides with galacto-and glucopyranose B-phosphoranes is described herein. The method involves the coupling of the sugar aldehydes with the ylides and the reduction of the double bond of the resulting sugar alkenes, in most of the cases by catalytic hydrogenation. The reduction with nickel boride or diimide is employed in some special cases. O-Benzyl protective groups are removed by catalytic hydrogenation either in the course of the reduction of the double bond or in a subsequent step, while O-isopropylidene groups are cleaved by treatment with Amberlite IR-120. In this way, eight free beta-D-(1-->6)-C-disaccharides have been prepared in 26-61% overall yield starting from B-linked formyl C-glycosides. These include C-linked analogues of the biologically active disaccharides allolactose (Gal beta 1,6Glc), gentiobiose (Glc beta 1,6Glc), and N-acetylamino disaccharides (GalNHAc beta,6Gal and GalNHAc beta 1,6Glc). Moreover, the synthesis of two alpha-D-(1-->6)-C-disaccharides is described from formyl C-furanosides. The limiting condition of the synthesis of these stereoisomers is the configurational instability of the alpha-linked formyl C-glycosides under the basic conditions of the Wittig olefination.