Selectively deoxygenated derivatives of beta-maltosyl-(1->4)-trehalose as biological probes

The four derivatives of beta-maltosyl-(1 --> 4)-trehalose have been synthesized, which are monodeoxygenated at the site of one of the primary hydroxyl groups. The tetrasaccharides were constructed in [2+2] block syntheses. Thus, 6'''-deoxy-beta-maltosyl-(1 --> 4)-trehalose was prepared by selective iodination of allyl 2,3,6,2',3'-penta-O-acetyl-beta-maltoside (3) followed by catalytic hydrogenolysis and coupling with 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-D-glucopyranosyl 2',3',6'-tri-O-benzyl-alpha-D-glucopyranoside (9), and 6 ''-deoxy-beta-maltosyl-(1 --> 4)-trehalose by selective iodination of allyl 4',6'-O-isopropylidene-beta-maltoside (14), coupling with 9, and one-step hydrogenolysis at the tetrasaccharide level. For the synthesis of 6'-deoxy-beta-maltosyl-(1 --> 4)-trehalose, the diol 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-D-glucopyranosyl 2',3'-di-O-benzyl-alpha-D-glucopyranoside (22) was selectively iodinated and glycosylated with acetobromomaltose followed by catalytic hydrogenolysis. The 6-deoxy-beta-maltosyl-(1 --> 4)-trehalose was obtained upon selective iodination of a tetrasaccharide diol.