A convenient synthesis of alkyl d-glycofuranosiduronic acids and alkyl d-glycofuranosides from unprotected carbohydrates

O-Glycosylation of a variety of long chain alcohols with totally unprotected uronic acids (d-glucuronic and d-galacturonic acids) and neutral carbohydrates (d-glucose, d-galactose, d-mannose and d-glucofuranurono-6,3-lactone), performed in heterogeneous media and promoted by Lewis acids (ferric chloride or boron trifluoride diethyl etherate), afforded alkyl d-glycofuranosiduronic acids and alkyl d-glycofuranosides, respectively, in high yields. Both chemoselectivity and anomeric stereoselectivity were enhanced by complexing agents, i.e. calcium or barium chloride.