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1

Total Synthesis of the Nephritogenoside Glycopeptide

Zhang H., Wang Y., Thurmer R., Al-Qawasmeh R., Voelter W.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

101-115

EN

A mild three-dimensional orthogonal protection scheme, based on Nps/Fmoc-groups for a-amino, benzyl residues for hydroxyl and carboxyl protection and 2-chlorotrityl esters as anchoring linkage proved to be a new effective approach for the synthesis of glycopeptides. The oligosaccharide moiety of the nephritogenoside glycopeptide is conveniently assembled via phenyl thioglycosides as glycosyl acceptors and phenyl thioglycosyl sulfoxides as donors, readily accessible from the thioglycosides by oxidation with m-chloroperbenzoic acid.

2

Model Studies of the Maillard Reaction of Arg-Lys with D-Glucose

Al-Abed Y., Callaway D., Kapurniotu A., Holak T., Voelter W.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

117-123

EN

Possible routes leading from Amadori product presusors to glucose-derived protein crosslinks has been suggested by model studies examining the fate of the Amadori products in vitro. For instance, the Amadori product can undergo dehydration to give 1,4 dideoxy-1-alkylamino-2,3-hexodiulose (AP-dione), which has been isolated by trapping with aminoguanidine. In a model reaction, we selected as an AGE target the dipeptide Na-Z-arg-lys. The proximity of the arginine and lysine residues to each other promotes stable intramolecular crosslink formation. Incubation of Na-Z-arg-lys with 10 equivalents of glucose in 0.2 M phosphate buffer (pH 7,4) at 37oC for five weeks produces at least 25 distinct reaction products upon fractionaction of this mixture by HPLC. Each fraction was isolated, concentrated, and analyzed for its reactivity with a polyclonal anti-AGEs that increase as a consequence of hyperglycemia and which are inhibited from forming in human subjects by treatment with the advanced glycation inhibitor aminoguanidine. The products present within one fraction (1.5% yield) were found to block antibody binding in a dose-dependent fashion. Further purification of this fraction by HPLC revealed the presence of one major (0.6% yield) immunoreactive compound. Characterization of this adduct by UV, ESMS and 1H-NMR spectra revealed the presence of intramolecular arg-lys-imidazole crosslink. This crosslink is non-fluorescent and acid labile and may represent an important class of immunoreactive AGE-crosslinks that form in vivo.

3

Epoxy Pyranoses, Chiral Synthons for Versatile Regio- and Stereocontrolled Functionalizations

Voelter W., Thurmer R., Al-Qawasmeh R.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

55-69

EN

From epoxy sugars, neighbouring an O-triflyl residue, efficient short-cut new routes to aminodeoxy, (amino acid)-deoxy, cyclopropanated, b-hydroxyketo or g-butyloractone pyranoses are developed.

4

Carbohydrate Chains and Their Binding Sites in Mistletoe Lectin I

Stoeva S., Maier T., Soler M., Voelter W.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

125-133

EN

The carbohydrate moieties, linked to mistletoe lectin 1 (ML-1) are characterized by enzymatic digestion of the individual A and B chains (MLA and MLB), HPLC separation of the (glyco)peptide digests and their sequence and mass spectrometric analysis. All carbohydrate chains are linked via Asn residues to the MLA protein molecule. A xylomannose-type oligosaccharide (1) structure (Man3Xyl1Fuc1GlcNac2) is attached to the Asn112 residue of the A chain. Three different glycosylation sites are identified for the B chain: oligosaccharide II (Man6GlcNac2) is found to be linked to Asn96 as well as Asn136 residues. In homologous mistletoe lectins, isolated from different harvest batches, oligosaccharide III (Man5GlcNac2) is attached to Asn136 instead of oligosaccharide II**.

5

Anhydro Sugars to Enantiomerically Pure Building Bloks: Efficient Syntheses of Y-Lactones and Furanoids

Al-Qawasmeh R., Al-Tel T., Abdel-Jalil R., Thurmer R., Voelter W.

Polish Journal of Chemistry

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1999

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vol. 73 nr 1

71-75

EN

Efficient and economic syntheses of multifunctional dihydrofurans, tetrahydrofurans and y-lactones are described. The regiochemistry of the ring junctions of the annulated oxa ring systems are controlled using temporary or permanent protection of the C-4 hydroxyl group.