Reactions of acylated pentoses and acylated methyl pentosides with dibromomethyl methyl ether. Preparation of bromo-deoxy-pentoses

Abstract

When acylated pentoses or acylated methyl pentosides are treated with dibromomethyl methyl ether and zinc bromide, acylated pentopyranosyl bromides are formed rapidly. In a further, slow reaction the pyranosyl bromides are converted into bromo-deoxy-pentosyl bromides, mostly with the bromo-substituent at C-2. Acetylated D-xylo-, D-arabino, and D-lyxo-pyranosyl bromides all yield 3,4-di-O-acetyl-2-bromo-2-deoxy-D-xylopyranosyl bromide, whereas tri-O-acetyl-D-ribopyranosyl bromide forms 3,4-di-O-acetyl-2-bromo-2-deoxy-D-arabino-pyranosyl bromide. The yields of 2-bromo-2-deoxy-products are low in the acetate series, but treatment of tri-O-benzoyl-D-xylopyranosyl bromide with dibromomethyl methyl ether gives a high yield of 2-bromo-2-deoxy-D-xylose derivatives.