N-(2,3,4,6-Tetra-O-acetyl-α-d-gluco-, β-d-gluco- and β-d-mannopyranosyl)-pyridinium salts were obtained and their structures were determined by 2D1H NMR spectroscopy. The compounds obtained were treated with a methanolic solution of sodium methylate. The β-anomer of thed-gluco derivative cyclizesviaBrigl's anhydride but the α anomer is competitively transformed according to the SN2 and SN1 mechanisms. The β-d-manno derivative does not cyclize under the conditions used. Comparison of the qualitative and quantitative results of the reaction studied enabled estimation of the influence of configuration at C-1 and C-2 on the course of cyclization. All product mixtures were separated by capillary gas chromatography (CGC) as exhaustivelyO-acetylated derivatives and their components were identified by coinjection with authentic materials.