Protected glucuronic acid (I) was converted to trichloroacetimidate (II) by treatment with trichloroacetonitrile and Cs2CO3.
Diol (III) was acetylated with Ac2O in the presence of dimethylaminopyridine to yield diester (IV), which was selectively hydrolyzed to monoacetate (V) by means of methanolic guanidine. Coupling of phenol (V) with imidate (II) by means of boron trifluoride etherate furnished the protected glucuronide (VI). The ester groups of (VI) were finally hydrolyzed by treatment with triethylamine in aqueous methanol.