Pentaacetylglucose is reacted with hydrogen bromide to give 2,3,4,6-tetra-"O"-acetyl-α--glucopyranosyl bromide (acetobromo glucose) (III) which yields with thiourea in acetone almost quantitatively the isothiuronium salt 2,3,4,6-tetra-"O"-acetyl-β--glucopyranosyl-1-isothiuronium bromide (IV).