Synthesis of a heteroglycuronan derivative containing the β-D-galactopyranosyluronic acid (1 → 3)-L-rhamnose repeating unit

Article abstract of DOI:10.1016/S0008-6215(92)84238-N

Helferich glycosylation of the cyanoethylidene L-rhamnose derivative 3 with the galactosyluronic bromide 2 gave the disaccharide 4 as a key intermediate in the synthesis of the monomer 13 for trityl-cyanoethylidene condensation (TCC). The following formation of the monomer 13, including introduction of a trityl group at O-3', proceeded in six steps. Because of the difficulty of some steps, an alternative route for 13 was tested. Model compounds 20, 21, and 22 were synthesized in order to confirm the stereoregularity of the products of the polycondensation. The polycondensation of the monomer gave D-GalpA-(1 → 3)-L-Rha-oligomer derivatives consisting mainly of three repeating units. This result is in contrast with the degree of polymerisation (dp ≥ 22) of other synthetic rhamnans, but is very similar to dp 2-7 of homo- and hetero-glucuronan derivatives.