New Synthetic Methods and Reagents for Complex Carbohydrates. VIII. Stereoselective <i>α</i>- and <i>β</i>-Mannopyranoside Formation from Glycosyl Dimethylphosphinothioates with the C-2 Axial Benzyloxyl Group

Abstract

Abstract The reactions of mannopyranosyl dimethylphosphinothioates and alcohols using silver perchlorate as an activator in the presence of molecular sieves 4A in benzene at room temperature gave the 1,2-trans-α-mannopyranosides in good yields. On the other hand, 1,2-cis-β-mannopyranosides could be obtained from the dimethylphosphinothioates by the combined use of iodine and 5 mol% triphenylmethyl perchlorate as an activating system. The syntheses of the derivatives of αMan(1→6)[αMan(1→3)]Man and βMan(1→4)GlcNAc units of glycoproteins by these methods are described.