SYNTHESIS OF 2-(ALPHA-D-GLUCOPYRANOSYL)BENZOIC ACID BY AN INTRAMOLECULAR FRIEDEL-GRAFTS REACTION

O-Acetyl-2,3,4-tri-O-benzyl-alpha-D-glucopyranosyl chloride reacted wi th silver tetrafluoroborate to give the internal C-glycoside, 1,2 ''-a nhydro-2'-(6 ''- O-acetyl-3 '',4 -di-O-benzyl-alpha-D-glucopyranosyl)p henylmethanol (2) with complete alpha-stereoselectivity and good yield . Oxidation of 2 by ruthenium (VIII) oxide gave the lactone, ro-(6-O-a cetyl-3,4-di-O-benzoyl-1,2-dideoxy-alpha- D-glucopyranoso)[2,1-c]-2-be nzopyran-1-one the structure of which was analysed by X-ray diffractio n. Alternatively, treatment of 2 by ozone followed by methanolysis gav e the title product in 60% yield. (C) 1996 Elsevier Science Ltd.