Formation of 3,6-anhydro-D-glucofuranosides in an acid-cata-lysed alcoholysis of partially tosylated D-glucose derivatives

Abstract

Partial esterification of D-glucose with 2 moles of tosyl chloride in pyridine at 14 °C gave 2,6-di-O-p-toluenesulphonyl-D-glucopyranose (1) as the main reaction product (55%) and 6-O-p-toluenesulphonyl-D-glucopyranose (2) as the minor product (33%). The reaction of D-glucono-1,5-lactone (3) with 5 moles of tosyl chloride in pyridine at -10 °C gave the corresponding 2,6-di-O-tosyl derivative 4 (62%), which was further treated with sodium borohydride in DMSO, at room temperature, to afford compound 1 in 95% yield. Acid catalysed alcoholysis of 1 in refluxing methanol or ethanol gave low yields of the corresponding 3,6-anhydro-D-glucofuranosides 5 (25%) and 6 (27%). However, the reaction of 1 with benzyl alcohol (130 °C) in the presence of toluene-p-sulphonic acid as a catalyst afforded the corresponding 3,6-anhydro-D-glucofuranoside 7 in an acceptable yield of 45%.