Structure of the glycopeptidolipid antigen of serovar 20 of the Mycobacterium avium serocomplex, synthesis of allyl glycosides of the outer di- and tri-saccharide units of the antigens of serovars 14 and 20, and serology of the derived neoglycoproteins

Abstract

The tetrasaccharide hapten released from the glycopeptidolipid (GPL) antigen of Mycobacterium avium serovar 20 has been characterized as O-(2-O-methyl-α-d-rhamnopyranosyl)-(1 → 3)-O-(2-O-methyl-α-l-fucopyranosyl)-(1 → 3)-α-l-rhamnopyranosyl-(1 → 2)-6-deoxy-l-talose. Syntheses are reported of allyl glycosides of the outer disaccharide unit of this hapten, O-(2-O-methyl-α-d-rhamnopyranosyl)-(1 → 3)-2-O-methyl-α-l-fucopyranose, and also of the outer di- and tri-saccharide units of the GPL antigen of M. avium serovar 14, O-(N-formyl-α-l-kansosaminyl)-(1 → 3)-2-O-methyl-α-d-rhamnopyranose and O-(N-formyl-α-l-kansosaminyl)-(1 → 3)-O-(2-O-methyl-α-d-rhamnopyranosyl-(1 → 3)-2-O-methyl-α-l-fucopyranose. The key steps in the latter synthesis involve the preparation of allyl 4-azido-4,6-dideoxy-3-C-methyl-2-O-methyl-α-l-mannopyranoside as a precursor for the N-formylkansosamine unit, followed sequentially by conversion into and use of a trichloroacetimidate as glycosyl donor for di- and tri-saccharide formation, O-deacylation, reduction, and N-formylation. The allyl glycosides, representative of the haptens from both serovars, have been converted into neoglycoproteins (NGPs) and their serological activities have been compared in the light of the structural relationship between them.