László Kalmár

Synthesis of N-glycopeptides applying glycoamino Acid building blocks with a combined fmoc/boc strategy.

Mono-, di- and trisaccharide representing the reducing terminal of the core structure of N-glycans were incorporated into Leu-Lys-Asn-Gly-Gly-Pro hexapeptide that is a partial structure of the Trp-cage mini-protein by linear assembly. These studies provide evidence that the used combination of Fmoc and Boc strategy and mild conditions result in glycopeptides in high purity and reasonable yield.

Synthesis of Fully O-Benzylated N-Linked Core Pentasaccharide Glycosyl Azide

The fully O-benzylated pentasaccharide glycosyl azide representing the common core structure of N-glycans was synthesized. The β-mannosidic linkage was created by C-2 epimerization of the initially introduced β-d- gluco-unit via DMSO/Ac2O oxidation followed by stereoselective reduction with tetrabutylammonium borohydride.

Synthesis of N-glycopeptides by convergent assembly

Electron-donating O-benzylated glycosylamine mono-, di- and trisaccharide representing the reducing terminal of the core structure of N-glycans were incorporated, in anomerically pure from into Leu–Lys–Asn–Gly-Gly–Pro hexapeptide that is a partial structure of the Trp-cage mini-protein by convergent assembly. According to our results acylation of electron-donating O-benzylated glycosylamine with peptide acid under the proposed new reaction conditions led to the formation of glycopeptide in good yield and in anomerically pure form for the first time. This convergent approach allows the synthesis of a series of glycopeptides containing different oligosaccharides without the need to resynthesize the peptide for each individual case.

Synthesis and MALDI-TOF MS Analysis of Protected Oligosaccharide Components of N-Glycoproteins

Essential components of N-glycoproteins were synthesized in octyl glycoside form starting from 3-O-allyl-D-glucose derivative. The β-mannosidic linkage was formed by the oxidation reduction method. MALDI-TOF mass spectrometry and its post-source decay (PSD) mode were used for identification and structural elucidation of protected synthetic oligosaccharides related to N-glycoproteins. Most fragments, identified in the PSD spectra, were products of the cleavage of glycosidic bonds.