The glycosyl-aldonolactone approach for the synthesis of β-d-Galf-(1→3)-d-Manp and 3-deoxy-β-d-xylo-hexofuranosyl-(1→3)-d-Manp
作者:Carla Marino、Alejandro Chiocconi、Oscar Varela、Rosa M de Lederkremer
DOI:10.1016/s0008-6215(98)00214-6
日期:1998.10
A convenient synthesis of free beta-D-Galf-(1 --> 3)-D-Manp (8a) is reported. The disaccharide is present as external unit in the lipopeptidophosphoglycan (LPPG) of Trypanosoma cruzi and internally in the lipophosphoglycan (LPG) of Leishmania. Condensation of 2,5,6-tri-O-benzoyl-D-mannono-1,4-lactone (1) with 1,2,3,5,6-penta-O-benzoyl-D-galactofuranose promoted by SnCl4, led to the B-glycosyl-lactone, a key intermediate for disaccharide 8a, readily obtained by successive reduction of the lactone with diisoamylborane and debenzoylation. As in the LPG of Leishmania the HO-3 group of the galactofuranose is glycosylated by alpha-D-Galp, we also synthesized 3-deoxy-beta D-xylo-hexofuranosyl-(1 --> 3)-D-Manp (8b) and p-nitrophenyl 3-deoxy-beta-D-xylo-hexofuranoside for studying the influence of HO-3 in the interaction with specific glycosidases. The disaccharide 8a, and its corresponding alditol, were good substrates for the beta-D-galactofuranosidase from Penicillium fellutanum, whereas the 3-deoxyglycosides were not hydrolyzed by the enzyme. (C) 1998 Elsevier Science Ltd. All rights reserved.