Synthesis of 5-aminopentyl mono- to tri-saccharide haptens related to the species-specific glycopeptidolipids of Mycobacterium avium-intracellulare serovars 8 and 21.

The preparation of pyruvate acetal-containing 5-aminopentyl mono-, di-, and tri-saccharide fragments related to serovars 8 and 21 of the species-specific glycopeptidolipid of Mycobacterium avium-intracellulare is described. The saccharides were constructed by sequential coupling of the suitably protected 4,6-O-[(S)-1-methoxycarbonylethylidene]-D-glucopyranosyl trichloroacetimidates 6 and 7 to Z-protected 5-aminopentanol, to give the serovar 21 monosaccharide fragment 9 upon deblocking; and to ethyl 2-O-benzoyl-4-O-benzyl-1-thio-alpha-L-rhamnopyranoside (18), to give the corresponding ethyl 1-thio-disaccharides 21 and 23, respectively. Subsequent N-iodosuccinimide-promoted coupling of the latter with Z-protected 5-aminopentanol followed by deblocking of the products afforded the corresponding disaccharide fragments 26 (serovar 8) and 27 (serovar 21), respectively. Condensation of 21 with Z-protected 5-aminopentyl 3,4-di-O-benzyl-6-deoxy-alpha-L-talopyranoside (28) and subsequent deblocking of the resulting trisaccharide gave the serovar 8 fragment 5-aminopentyl O-(4,6-O-[(S)-1-carboxyethylidene]-3-O-methyl-beta-D-glucopyranosyl)- (1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)-6-deoxy-alpha-L-talopyranos ide (30).