Synthesis of oligosaccharides of motifs D and E of arabinogalactan present in Mycobacterium tuberculosis.

Syntheses of the ethyl glycosides of 5-O-(beta-D-galactofuranosyl)-beta-D-galactofuranose and 5-O-(alpha-D-arabinofuranosyl)-6-O-(beta-D-galactofuranosyl)-beta-D-galactofuranose present in motifs D and E of Mycobacterium tuberculosis arabinogalactan, respectively, have been presented. The pentenyl-mediated O-glycosylation reaction was utilized to obtain the disaccharide of motif D. The first coupling reaction to prepare the inner disaccharide portion of motif E was accomplished by trichloroacetamidate method while the installation of the terminal sugar by pentenyl glycosylation approach was successful.