Non-natural glycosphingolipids and structurally simpler analogues bind HIV-1 recombinant Gp120

Synthesis, gp120 binding and anti-HIV activity of fatty acid esters of 1,1-linked disaccharides

Inspired by the anti-human immunodeficiency virus (HIV) activity of analogues of β-galactosylceramide (GalCer), a set of mono- and di-saccharide fatty acid esters were designed as GalCer mimetics and their binding to the V3 loop peptide of HIV-1 and anti-HIV activity evaluated. 1,1-linked Gal-Man and Glu-Man disaccharides with an ester on the Man subunit bound the V3 loop peptide and inhibited HIV infectivity in single round infection assays with the TZM-bl cell line. IC(50)'s were in the 50 μM range with no toxicity to the cells at concentrations up to 200 μM. These compounds appear to inhibit virus entry at early steps in viral infection since they were inactive if added post viral entry. Although these compounds were found to bind to the V3 loop peptide of gp120, it is not clear that this interaction is responsible for their anti-HIV activity because the relative binding affinity of closely related analogues did not correlate with their antiviral behavior. The low cytotoxicity of these 1,1-linked disaccharide fatty acid esters, combined with the easy accessibility to structurally diverse analogues make these molecules attractive leads for new topical anti-viral agents.

Design, synthesis, and validation of a branched flexible linker for bioactive peptides

A branched flexible linker that incorporates a fluorescent dansyl moiety was synthesized and used to connect two high affinity NDP-alpha-MSH ligands or two low affinity MSH(4) ligands. The linker was incorporated into the conjugate by solid-phase synthesis. In vitro biological evaluations showed that potency of binding to the human melanocortin 4 receptor was not diminished for linker-ligand combinations relative to the corresponding ligand alone.

Efficient synthesis of Man2, Man3, and Man5 oligosaccharides, using mannosyl iodide donors

[reaction: see text] A highly efficient protocol for making Man(3) and Man(5) oligosaccharides with use of orthogonally protected glycosyl iodide donors has been developed. Glycosylation of a C-2-O-acetyl mannosyl iodide donor in the presence of silver triflate at -40 degrees C initially gave a mixture of the desired alpha-linked mannoside and an orthoacetate resulting from attack at the C-2 acetate. However, upon warming to room temperature the orthoacetate quantitatively rearranged to the desired oligosaccharide. Employing a 3,6-dihydroxy acceptor and subjecting it to double glycosidation quickly afforded high mannose sugars in nearly quantitative yields. Glycosyl iodide donors offer advantages over previously reported chloride donors as the reactions are faster, proceed in higher yields, and are not diminished in higher order constructs. These studies continue to dispel the notion that glycosyl iodides are too reactive to be of synthetic utility.

C-Glycoside analogues of beta-galactosylceramide with a simple ceramide substitute: synthesis and binding to HIV-1 gp120

The synthesis and HIV-1 gp120 binding of C- and aza-C-glycoside analogues of beta-galactosylceramide (GalCer) that contain a simple C-17 hydrocarbon chain as a ceramide substitute are described. Both compounds originate from stearic acid, and a carbohydrate-derived thioacetal-alcohol, and their syntheses are potentially general for beta-C-galactosides and their aza-C-partners. They showed potent and specific affinity for gp120 in an assay based on the change of surface pressure when the glycolipid monolayers were exposed to solutions of gp120. Interestingly, the aza-C-glycoside exhibited a significantly higher affinity than GalCer, whereas the C-glycoside was as active as GalCer.

New bicyclam-GalCer analogue conjugates: synthesis and in vitro anti-HIV activity

The synthesis of bipharmacophore anti-HIV compounds which, in a single molecule, combine two ligands, that is, the bicyclam AMD3100 and a GalCer analogue, that might inhibit several steps of the complex virus/cell cascade interactions has been performed. The 'double-drug' Gal-AMD3100 conjugates elicited inhibitory effects on T (or X4)-tropic HIV-1 replication in all CXCR4 expressing cell lines with EC(50) values ranging from 0.25 to 6.0 microM which were however approximately 40- to 125-fold lower than that of AMD3100. Concerning the mechanism of inhibition of the Gal-AMD3100 conjugates, experiments performed with X4 or R5HIV-1 strains and GHOST cells genetically modified to express CD4 and CXCR4 or CCR5 indicated clearly that the conjugates interact with CXCR4 and not with CCR5.