Synthesis of carbocyclic analogues of the mannosyl trisaccharide: ether- and imino-linked methyl 3,6-bis(5a-carba-α-d-mannopyranosyl)-3,6-dideoxy-α-d-mannopyranosides

Carbocyclic analogues 2 and 3 of the “trimannosyl structure 1”, methyl 3,6-bis(5a-carba-α-d-mannopyranosyl)-3,6-dideoxy-α-d-mannopyranosides bonded by way of respective ether and imino linkages, were synthesized. The ether 2 had no inhibitory activity against α-d-mannosidase; in contrast, the imino compound 3 was a mild inhibitor. Furthermore, the inhibitory activity of 4, related to 3 by introduction of unsaturation between C-5 and C-5a of the carba-sugar moieties, was shown to be somewhat greater.