No abstract

[structure] C-Glycosides of N-acyl 2-amino-2-deoxygalactose (acyl = MeCO, CF(3)CO, t-BuOCO) are available in a stereoselective manner by trapping of an anomeric radical with an activated alkene. Using anomeric selenides, radical generation and trapping is carried out under conditions that avoid competitive reduction, and this chemistry has been applied to the synthesis of the novel C-glycoside analogue of O-benzyl alpha-D-GalNAc.

[reaction: see text] Starting from readily available precursors, selenoglycosides derived from GalNAc, GlcNAc, and ManNAc were prepared by either a one- or a two-step process. The anomeric selenides underwent facile C-Se homolysis to provide the corresponding anomeric radicals, which were trapped with alkenes to give C-glycosides. This provides a general entry to alpha-C-glycosides based on 2-amino-2-deoxy sugars that is also applicable to disaccharide variants.