Synthesis of oligosaccharides of motifs D and E of arabinogalactan presentin 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-galactofu ranosyl)-beta -D-galactofuranose present in motifs D and E of Mycobacterium tuberculosis arabinogalactan, respectively, have been presented. The pente nyl-mediated O-glycosylation reaction was utilized to obtain the disacchari de of motif D. The first coupling reaction to prepare the inner disaccharid e portion of motif E was accomplished by trichloroacetamidate method while the installation of the terminal sugar by pentenyl glycosylation approach w as successful.