Synthesis of Maleimide-Activated Carbohydrates as Chemoselective Tags for Site-Specific Glycosylation of Peptides and Proteins

Abstract

An array of maleimide-activated mono- and oligosaccharides were synthesized to permit site-specific glycosylation of cysteine-containing peptides and proteins. Maleimide-activated monosaccharides, in which the native alpha- or beta-O-glycosidic linkages found for nonreducing terminal sugars of native glycoproteins are preserved, were prepared using 2'-aminoethyl glycosides as the key intermediates. In addition, a native high-mannose type oligosaccharide, Man(9)GlcNAc(2)Asn, was converted into its maleimide-activated form by taking advantage of the existing amino group in the Asn portion. The application of these maleimide-activated carbohydrates was exemplified by the site-specific glycosylation of a 36-mer HIV-1 gp41 peptide, T20, which is a potent inhibitor against HIV infection. The chemoselective ligation was found to be rapid, highly efficient, and essentially quantitative. Tagging the biologically active peptide with a mannose and/or oligomannose moiety will be useful for targeting the drug to macrophage and dendritic cells, which are primary targets for HIV-1 infection and are expressing mannose- and oligomanose-specific receptors on their surface. In combination with site-specific mutagenesis, the maleimide-activated carbohydrates can serve as generally applicable tags for site-specific glycosylation of proteins via the highly efficient maleimide-thiol ligation reaction.

Synthesis and Biological Evaluation of Fucoidan-Mimetic Glycopolymers through Cyanoxyl-Mediated Free-Radical Polymerization

“…42 Hence, 2-Azidoethyl 2,3,4-Tri-O-acetyl-α-Lfucopyranoside (1) (Scheme 1) was deemed as a suitable starting material due to its inherent α-fucosidic bond and the accessible terminal azide functionality. 1 was synthesized according to a known procedure 39 and the azide reduced to amine by catalytic hydrogenation. Initial reactions gave low yields due to O→N acetyl group migration and dimerization at the amine, all observed by 1 H-NMR.…”

Noncovalent PEGylation via Lectin–Glycopolymer Interactions

“…2-azidoethyl α-L-fucose was synthesized as described. 42 For the click reaction, stoichiometric amounts of Alk-PEG and 2-azidoethyl α-L-fucose were combined in t-butanol/water (5:1) in the presence of copper sulfate (0.1 eq.) and sodium ascorbate (0.2 eq.)…”

Forces and Dynamics of Glucose and Inhibitor Binding to Sodium Glucose Co-transporter SGLT1 Studied by Single Molecule Force Spectroscopy

“…Therefore, 2Ј-aminoethyl ␤-D-glucopyranoside was synthesized as described (32) and N-acylated with N-succinimidyl 6-(acetylthio)hexanoate as previously described for "tris-nitrilotriacetic acid" (33) yielding the product AcS-hex-glc. Immediately before coupling to the AFM tip, the acetyl group was removed with hydroxylamine (34) to obtain a free thiol, abbreviated as hex-glc (Fig.…”