Unsaturated carbohydrates. Part VI. A modified synthesis of 2-hydroxyglycal esters, and their conversion into esters of 2,3-didehydro-3-deoxyaldoses

Abstract

Conversion of acylglycosyl bromides into the corresponding iodides by treatment with sodium iodide in acetone solution and subsequent reaction with diethylamine affords an improved means of preparing acylated 2-hydroxyglycals. The allylic rearrangement which occurs when tetra-O-acetyl-2-hydroxy-D-glucal is heated in acetic acid solution is now shown to take place with 2-hydroxyglycal esters derived from D-galactose, D-xylose, 6-deoxy-D-glucose, and 6-deoxy-D-galactose, and, from each reaction studied, one crystalline 2,3-didehydro-3-deoxyaldose ester has been obtained in good yield.