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

All of the monodeoxy analogues of methyl 3,6-di-O-alpha-D-mannopyranosyl-alpha-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.