Synthesis of D-galactal-derived vinyl epoxide, as glycosyl donor devoid of any protective group

6-O-Benzyl protected D-galactal-derived vinyl epoxide had demonstrated to be an excelent, completely regio- and stereoselective glycosyl donor with O-nucleophiles (alcohols), particularly useful in carbohydrate chemistry and synthesis of oligosaccharides. However, the unsurmountable incompatibility of the deprotection protocol for O-benzyl protective group (H2/Pd-C) with other functional groups present in the molecule may constitute a limit to the synthetic use of this epoxide. Now we have found that the corresponding D-galactal-derived epoxide bearing a free, not protected 6-OH functionality, glycosilates alcohols in a completely regio- and stereoselective fashion, as the corresponding 6-OBn substituted epoxide, affording corresponding O-glycosides having the same configuration as the starting epoxide, in a directly substrate-dependent glycosylation process. In this way, the limit related to the use of O-benzyl protection appears to be overcome