The altruronic acid derivative (III) was synthesized starting from the described glycoside (I). Reduction of the azido group of (III) by hydrogenation over Pd/C provided the corresponding amine (II), which was then acylated by means of trichloroacetyl chloride and triethylamine.

Hydrolysis of phthaloyl and acetyl groups of the galactose thioglycoside derivative (IV) by treatment with ethylenediamine afforded amine (V), which was subsequently converted to the trichloroacetamide (VI). Further acetylation of the hydroxyl group of (VI) employing Ac2O in pyridine produced the corresponding acetate ester (VII). Coupling of (VII) with the altruronic acid derivative (III) was carried out via activation of the thioglycoside by means of N-iodosuccinimide and triflic acid to furnish the fully protected disaccharide (VIII). Basic hydrolysis of the ester and amide groups of (VIII), followed by N-acetylation with Ac2O in MeOH yielded the diacetamido derivative (IX). Finally, hydrogenolytic cleavage of the O-benzyl group of (IX) with simultaneous azide reduction afforded the target disaccharide.