Conjugates of biologically active lipid a-subunit analogs with 3-deoxy-d-manno-2-octulosonic acid (KDO) and its methyl ester

Synthesis of Kdo-trisaccharide derivatives of chlamydial and enterobacterial LPS containing carboxyl-reduced or β-configurated Kdo-residues

Five allyl glycosides corresponding to the 3-deoxy-D- manno-2-octulosonic acid (Kdo) containing genus-specific LPS epitope of Chlamydia were synthesized. Compounds 5 and 22 contain one carboxyl-reduced Kdo moiety linked to O-4 of the proximal Kdo unit, whereas the analogues 28, 34 and 36 each contain one β-linked Kdo-residue within the trisaccharide sequence Kdo p-(2→8)-Kdo p-(2→4)-Kdo p. Elaboration of the carboxyl-reduced derivatives was achieved by BF3•Et2O-catalyzed coupling of Kdo-fluoride derivatives 1 or 14 with the 7,8- O-carbonyl-derivative 2. The β-linked oligosaccharides were obtained by Helferich-glycosidation of the respective Kdo-disaccharide bromide derivatives 26 and 31. The deprotected compounds - characterized by H and 13C NMR spectroscopy - are suitable haptens for the immunochemical study of monoclonal antibodies directed against the Kdo-region of chlamydial and enterobacterial LPS.

Anomeric O-acylation of Kdo using alkyl and aryl isocyanates

To develop a convenient method for the preparation of an alpha-Kdo derivative carrying a functional spacer at the reducing end, we examined anomeric O-acylation using Kdo and halogenated alkyl/aryl isocyanates as nucleophile and electrophiles, respectively. Reaction of a Kdo derivative with 2-chloroethyl isocyanate in the presence of DMAP gave an alpha-spiro product (82%) and an alpha-Kdo derivative of a dimeric isocyanate adduct (10%). Similar reaction with 4-(chloromethyl)phenyl isocyanate gave only the corresponding alpha-spiro product (81%). The NMR data show that the pyranose rings of both the alkyl and aryl spiro products adopt the 5C2 conformation. Thus, we accomplished alpha-selective anomeric O-acylation by coupling the Kdo derivative with alkyl and aryl isocyanates.

Synthesis of fluorescently labeled UDP-GlcNAc analogues and their evaluation as chitin synthase substrates

[structure: see text] Chitin synthase (CS) polymerizes UDP-GlcNAc to form chitin (poly-beta(1,4)-GlcNAc), a key component of fungal cell wall biosynthesis. Little is known about the substrate specificity of chitin synthase or the scope of substrate modification the enzyme will tolerate. Following a previous report suggesting that 6-O-dansyl GlcNAc is biosynthetically incorporated into chitin, we became interested in developing an assay for CS activity based on incorporation of a fluorescent substrate. We describe the synthesis of two fluorescent UDP-GlcNAc analogues and their evaluation as chitin synthase substrates.

Stereoselective synthesis of the alpha-glycoside of a KDO "C"-disaccharide

The reaction of tert-butyl (4,5,7, 8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosyl chloride)onate donor 7 with the 6-formylgalactopyranoside acceptor 4 in the presence of SmI(2) provided only the KDO alpha-C-disaccharide 8. The bulky tert-butyl ester in the donor was used to reverse the stereochemical outcome of C-glycosylation, stereoselectively forming the alpha-"C"-disaccharide of KDO.

Synthesis of allyl 6-O-(3-deoxy-alpha- and -beta-D-manno-oct-2- ulopyranosylonic acid)-(1----6)-2-deoxy-2-[(3R)-3-hydroxytetradecanamido]- beta-D-glucopyranoside 4-phosphate and of the copolymer of the alpha anomer with acrylamide

The title disaccharides were synthesized by mercuric cyanide-catalyzed condensation of methyl (4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-oct-2-ulopyranosyl bromide)onate and allyl 2-[(3R)-3-acetoxy-tetradecanamido]-3-O-benzyl-2-deoxy-beta-D- glucopyranoside, followed by phosphorylation of the alcoholic function of the amino sugar. The phosphorylated anomers were separated by chromatography and deprotected by conventional methods. Polymeric material was obtained by copolymerisation, catalyzed by peroxosulphate and N,N,N',N'-tetramethylethylenediamine, of the alpha anomer with acrylamide; it contained ca. one disaccharide unit for 18 acrylamide residues.

Synthesis of alpha-Kdo-(2----4)-Kdo disaccharide derivatives and their conjugation with a protected form of GLA-60, a biologically active analog of a lipid A subunit

A variety of the protected O-[(3-deoxy-alpha-D-manno-2-octulopyranosyl)onic acid]-(2----4)-3-deoxy-D-manno-2-octulosonic acid [alpha-Kdo-2(2----4)-Kdo] derivatives have been synthesized starting from methyl [2-(trimethylsilyl)ethyl 4,5,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosid] onate. Some of these were conjugated with a protected form of a bacterial lipid A subunit-analog (GLA-60) having beneficial immunopharmacological activity, namely benzyl 2-[(3R)-3-(benzyloxy-methoxy)tetradecanamido]-2-deoxy-4-O- (diphenoxyphosphinyl)3-O-[(3R)-3-tetradecanoyloxytetradecanoyl+ ++]-beta -D-glucopyranoside.

Immunopharmacological activities of 2-keto-3-deoxyoctonic acid-(alpha 2----6)-linked 4-O-phosphono-D-glucosamine derivatives carrying N- and 3-O-acyl substituents

The immunopharmacological activities of 2-keto-3-deoxyoctonic acid (KDO)-(alpha 2----6)-linked lipid A-subunit analogs, 4-O-phosphono-D-glucosamine derivatives carrying N- and 3-O-acyl substituents, were compared with those of the corresponding analogs without KDO, GLA-27, GLA-47, and GLA-60. Among the analogs tested, GLA-60, a 4-O-phosphono-D-glucosamine carrying N-3-hydroxytetradecanoyl and 3-O-3-tetradecanoyloxytetradecanoyl groups, exhibited the most intensive activities in terms of mitogenicity, adjuvanticity, and mediator (tumor necrosis factor and colony-stimulating factor) induction. Binding (alpha 2----6) of KDO to GLA-60 failed to enhance the activities. Similarly, the activities of GLA-27 and GLA-47 were also decreased by introduction of KDO to the O-6 of the analogs. This indicates that the strengths of the activities of the subunit analogs depend on the kinds of N- and 3-O-linked acyl substituents and not on the presence of the KDO linked to the O-6.