Synthetic arabinofuranosyl oligosaccharides as Mycobacterial arabinosyltransferase substrates
摘要:
A series of arabinofuranosyl oligosaccharides found as constituent parts of the polysaccharide portion of the cell wall of Mycobacterium tuberculosis have been chemically synthesized. Screening of these oligosaccharides as substrates for arabinosyltransferases present in mycobacterial membrane preparations suggests that modified oligosaccharide analogs as small as disaccharides may be inhibitors of glycan biosynthesis. Such inhibitors would be of potential utility as lead compounds in the identification of new drugs for the treatment of mycobacterial infections. (C) 1998 Elsevier Science Ltd. All rights reserved.
Arabinofuranosyl Oligosaccharides from Mycobacteria: Synthesis and Effect of Glycosylation on Ring Conformation and Hydroxymethyl Group Rotamer Populations
作者:Francis W. D'Souza、Joseph D. Ayers、Patrick R. McCarren、Todd L. Lowary
DOI:10.1021/ja993543l
日期:2000.2.1
A series of alpha-D-arabinofurnnosyl oligosaccharides (2-8) that an fragments of the arabinan portions of two polysaccharides present in the cell wall of Mycobacterium tuberculosis have been synthesized. Preparation of the oligosaccharides involved the sequential addition of arabinofuranosyl residues from thioglycoside donors to methyl glycoside accepters. High-resolution NMR studies on the final products provided all (3)J(H,H) values, which were in turn used in PSEUROT 6.2 calculations to determine both the identity and equilibrium populations of preferred conformers for each furanose ring in these glycans. Comparison of the ring conformers present in 2-8 with these available in the parent monosaccharide, methyl alpha-D-arabinofuranose (16), allowed the determination of the effect of glycosylation upon ring conformation. At equilibrium, 16 exists as an approximately equimolar mixture of T-0(4) (North, N) and T-2(3) (South, S) conformers. These studies showed that glycosylation of 16 at OH5 resulted in no significant change in conformer identity or population relative to 16. However, glycosylation of OH3 resulted in a change in the identity of the N species (to E-O) and a significant favoring of this conformer at equilibrium. These trends were seen in all of the oligosaccharides. The populations of the three possible staggered rotamers (gg, gt, tg) about the C4-C5 bond were essentially the same for all residues in 2-8, and thus this equilibrium does not appear to be sensitive to glycosylation.