A convenient synthesis of alkyl d-glycofuranosiduronic acids and alkyl d-glycofuranosides from unprotected carbohydrates
摘要:
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. (C) 1998 Elsevier Science Ltd. All rights reserved
O-Glycosidation of totally O-unprotected D-galacturonic acid 1 in THF provides α-pyranosides 4a when promoted with BF3·OEt2 whereas β-furanosides 6β were obtained in the presence of FeCl3; when the same reaction is performed with D-glucuronic acid 2 or ‘D-glucurone’3, alkyl-D-glucofuranosidurono-6,3-lactones 7 are synthesized in excellent yields and high β-selectivity.
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. (C) 1998 Elsevier Science Ltd. All rights reserved