Palladium-Catalyzed α-Stereoselective O-Glycosylation of O(3)-Acylated Glycals

Pd(MeCN)2Cl2 enables the alpha-stereoselective catalytic synthesis of 2,3-unsaturated O-glycosides from O(3)-acylated glycals without the requirement for additives to pre-activate either donor or nucleophile. Mechanistic studies sug-gest that, unlike traditional (η3-allyl)palladium-mediated processes, the reaction proceeds via an alkoxy-palladium inter-mediate that increases the proton acidity and oxygen nucleophilicity of the alcohol. The method is exemplified with the syn-thesis of a range of glycosides and glycoconjugates of synthetic utility.