Syntheses of deoxy analogues of methyl 3,6-di-O-α-d-mannopyranosyl-α-d-mannopyranoside for studies of the binding site of Concanavalin A

All of the monodeoxy analogues of methyl 3,6-di-O-α-d-mannopyranosyl-α-d-mannopyranoside have been synthesized together with two dideoxy (2,3′- and 4,3′-) analogues. The 2′- and 2″-deoxy functions were introduced by NIS-promoted couplings with 2,3,4-tri-O-acetyl-d-glucal as donor, followed by reduction of the resulting 2′- and 2″-iodo derivatives, whereas the 3′-, 3″-, 4′-, 4″-, 6′-, and 6″-deoxy functions were introduced by using known deoxyglycosyl chlorides as donors in coupling reactions promoted by silver trifluoromethanesulfonate. The 2- and 4-deoxy functions on the central mannose residue were introduced by displacement, using triiodoimidazole and triphenylphosphine, of a hydroxyl group by iodine on suitably protected derivatives followed by reduction of the resulting iodo analogues.