(2-O-hexadecyl)PI], were tested as substrates or inhibitors of glycosylphosphatidylinositol (GPI) bio-synthetic pathways using cell-free systems of the proto-zoan parasite Trypanosoma brucei (the causative agent of human African sleeping sickness) and human HeLa cells. Neither these compounds nor their N-acetyl derivatives are substrates or inhibitors of GPI bio-synthetic enzymes in the HeLa cell-free system but are potent inhibitors of GPI biosynthesis in the T.brucei cell-free system. GlcN-(2-O-hexadecyl)PI was shown to inhibit the first α-mannosyltransferase of the trypano-somal GPI pathway. The N-acetylated derivative GlcNAc-(2-O-octyl)PI is a substrate for the trypano-somal GlcNAc-PI deN -acetylase and this compound, like GlcN-(2-O-octyl)PI, is processed predominantly to Man 2 GlcN-(2-O-octyl)PI by the T.brucei cell-free system. Both GlcN-(2-O-octyl)PI and GlcNAc-(2-O-octyl)PI also inhibit inositol acylation of Man 1-3 GlcN-PI and, consequently, the addition of the ethanolamine phosphate bridge in the T.brucei cell-free system. The data establish these substrate analogues as the first generation of in vitro parasite GPI pathway-specific inhibitors.

No abstract

This report describes a simple synthesis of 2-azido-3,4,6-tri-O-benzyl-2-deoxy-d-glucopyranose. Glycosylation using this as well as 2-azido-3,4,6-tri-O-benzyl-2-deoxy-d-galactopyranose and -mannopyranose was achieved with the aid of a reagent system consisting of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine, and its modifications. O-(2-Acetamido-2-deoxy-β-d-glucopyranosyl)-(1→4)-O-α-d-mannopyranosyl-(1→4)-α-d-mannopyranose, the repeating unit of the main chain of the O-specific cell wall polysaccharide of E. coli 058 was synthesized.

Dehydrative glycosylations of the 2-, 3-, 4-, and 6-OH groups of d-glucopyranose with hepta-O-benzyl derivatives of glucobioses (O-d-glucopyranosyl-(1→n)-d-glucopyranose; n = 2, 3, 4, or 6) and lactose, in the presence of a ternary mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, and triethylamine in dichloromethane showed that the selectivity of the reaction depended on the anomeric configuration and the linking position to the reducing tribenzylglucose moiety of the nonreducing tetrabenzylglucosyl residue and on the class of the OH group to be glycosylated. The use of a quaternary mixture of p-nitrobenzenesulfonyl chloride, silver trifluoromethanesulfonate, N,N-dimethylacetamide, and triethylamine made all but the β(1→2)-linked biosyl donor undergo α-condensation. Several new linear trisaccharides were obtained via debenzylation of the condensates.

The title β-d-ManNAcA-donor, the α-bromide of methyl 2-benzoyloxyimino-2-deoxy-d-arabino-hexopyranuronate 9, has been prepared from d-glucuronolactone in an overall yield of 21% for the seven steps required, all intermediates being securable in crystalline form. Key compounds were the 2-acetoxy-d-glucuronal ester 6 and its hydroxylaminolysis product, the 1,5-anhydro-d-fructuronate oxime 7, the latter elaborating 9 on O-benzoylation (→8) and photobromination. —The utility of 9 as a suitable β-d-ManNAcA donor rests on two ensuing reactions: first, Koenigs-Knorr type glycosidations, with N-blocked 2-aminoethanols as spacer substrates, or with the 6-OH of an otherwise protected glucoside (16), produce β-selectivities of 20 : 1 or better, and second, the oxime reduction of the β-glycosides, thus obtained, proceeds in an essentially stereospecific manner to yield, upon N-acetylation, the 2-acetamido-2-deoxy-β-d-mannosiduronates. —The methodology elaborated was used to prepare some novel artificial glycolipids, e.g. the (myristoylamino)ethyl 6-O-(2-acetamido-2-deoxy-β-d-mannopyranosyluronic acid)-α-d-glucopyranoside (25) and its (stearoylamino)ethyl analog (26), that are being evaluated as recognition markers for liposomes.