Semi-orthogonality of O-pentenyl and S-ethyl glycosides: application for the oligosaccharide synthesis

Novel semi-orthogonal glycosylation strategy with the use of O-pentenyl and thioglycosides has been developed. According to this technique both armed and disarmed thioglycosides can be selectively activated with MeOTf in the presence of either armed or disarmed O-pentenyl glycosides. The applicability of this novel strategy for the synthesis of a trans–cis glycosylation pattern, not accessible via conventional armed–disarmed approach, has been demonstrated for the synthesis of a linear tetrasaccharide derivative.