Modified Curtius rearrangements in the selective cleavage of β-D-glucosiduronic acid and β-D-glucosiduronamide linkages

Abstract
The selective cleavage of .beta.-D-glucosiduronic acid linkages in permethylated carbohydrates is achieved by modified Curtius rearrangements involving reaction of glycosiduronic acids with diphenylphosphoroazidate or treatment of glycosiduronamides with lead tetraacetate, each in the presence of tert-butanol or benzyl alcohol to give 5-tert-butyloxycarbonylamino- or 5-benzyloxycarbonylaminopentopyranosides, followed by mild acid hydrolysis (for tert-butyl) or hydrogenolysis (for benzyl) of the carbamates to give pentodialdoses (from uronic acids) with retention of substituents, and with exposure of aglyconic hydroxyl groups. The liberated functional groups are available for derivative formation. These reaction sequences were performed on permethylated derivatives of D-glucuronic acid, gentiobiouronic acid, 2-O-.beta.-D-glucopyranosyl-D-galacturonic acid and gum arabic.

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