Tetra-0-benzyl-a-D-glucopyranosyl bromide in dichloromethane reacts stereospecifically with solutions of phenols in aqueous sodium or potassium hydroxide, in the presence of phase transfer catalysts, to give good yields of tetra-O-benzyl aryl-8-D-glucopyranosides which are converted into the corresponding aryl 8-D-glucopyranosiduronic acids by sequential catalytic debenzylation and catalytic oxidation. Many aromatic compounds are metabolised by animals to phenolic derivatives which then become conjugated with D-glucuronic acid prior to their excretion. To assist in the unequivocal identification and quantification (e.g. by radioassay procedures) of such conjugated metabolites it is therefore necessary to have readily available, a convenient synthesis of aryl 8-D-glucopyranosiduronic acids. In this laboratory, except with simple phenols, attempts to form aryl 8-D -glucopyranosiduronic acids by direct reaction of phenols with methyl (2,3,4-tri-O-acetyl-a-D -glucopyranosylbromide)uronate by any of the many variations described for Koenigs-Knorr procedures 132 were completely unsuccessful or gave low yields. Also for some complex aromatic