CYCLIZATION OF -O-ACETYL-D-GLUCO-AND-D-MANNOPYRANOSYL)-PYRIDINIUM SALTS IN A METHANOLIC SOLUTION OF SODIUM METHYLATE

N-(2,3,4,6-Tetra-O-acetyl-alpha-D-gluco-, beta-D-gluco- and beta-D-man nopyranosyl)-pyridinium salts were obtained and their structures were determined by 2D H-1 NMR spectroscopy. The compounds obtained were tre ated with a methanolic solution of sodium methylate. The beta-anomer o f the D-gluco derivative cyclizes via Brigl's anhydride but the alpha anomer is competitively transformed according to the S(N)2 and S(N)1 m echanisms. The beta-D-manno derivative does not cyclize under the cond itions used. Comparison of the qualitative and quantitative results of the reaction studied enabled estimation of the influence of configura tion at C-1 and C-2 on the course of cyclization. All product mixtures were separated by capillary gas chromatography (CGC) as exhaustively O-acetylated derivatives and their components were identified by coinj ection with authentic materials.