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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010The Application of the New Tin(IV) Chloride Deprotection forthe Preparation of Glycosylated PeptidesOrsolya Szolomájer-Csikós 1 , Kinga Rákosi 1 , Orsolya Hegyi 1 ,László Kalmár 2 , János Kerékgyártó 2 , and Gábor K. Tóth 11 Department of Medical Chemistry,Faculty of General Medicine, University of Szeged,6720, Szeged, Hungary; 2 Department of Botany, Bio-organic Laboratory, University ofDebrecen, Faculty of Sciences and Technology, Debrecen, 4032, HungaryIntroductionGlycopeptides plays crucial roles in various biological functions, especially in biologicalrecognition events, signal transduction, and immune response. The carbohydrate moietiesare attached through the oxygen in the side-chain of serine/threonine in O-linkedglycoproteins or through the carboxyamide nitrogen of asparagine in case of N-linkedglycoproteins. The rational preparation of the glycosylated peptides is still one of the mostchallenging tasks of peptide chemistry especially of those having oligosaccharide moieties.There are two main strategies: the stepwise approach (normally proceeds through aprotected glycosylated amino acid intermediate which usually serves as the building blockfor a solid-phase construction of a peptide sequence) and the convergent method (therequired carbohydrate chain and peptide are each built independently, and the amide orester linkage is created in the synthesis), both of them can be implemented in liquid orsolid-phase. We describe here a mixed Fmoc/Boc solid-phase synthesis strategy for thepreparation of glycopeptides by using a new, mild and selective Boc deprotecting agent.Results and DiscussionAccording to literature the Fmoc-protected glycosylated asparagine and serine derivativesproved to be suitable building blocks for the solid-phase peptide synthesis. In some casesthe preparation of Boc-protected glycosylated amino acid building blocks is moreconvenient than the Fmoc protected ones. For the incorporation of the Boc-protectedglycosylated amino acid derivatives in the model peptides as selective Boc deprotectingagent-tin(IV) chloride was used [1]. The glycopeptides in this case were synthesised usingthe Fmoc chemistry on a TFA cleavable Rink-amide MBHA resin. According to ourinvestigations other resins commonly used in Fmoc chemistry (Rink amide, 2-chlorotritylresin, Wang resin) showed leakage of the peptide from the resin during cleavage withtin(IV) chloride, except the Rink-amide MBHA. As model peptides we used a shorterfragment of the Trp-cage miniprotein (Leu-Lys-Asn*-Gly-Gly-Pro) [2] and an aggrecanfragment, from the most glycosylated region of the protein (Gly-Val-Glu-Asp-Ile-Ser*-Gly-Leu-Pro-Ser-Gly), where * is site of glycosylation. As building blocks N -Boc-protected[GlcNAc( 1-N)]Asn, [GlcNAc( 1-4)GlcNAc( 1-N)]Asn, [Man( 1-4)GlcNAc( 1-4)GlcNAc( 1-N)]Asn and [Xil(Bz) 3 ( 1-O)]Ser were used (Figure 1).The synthesis of Leu-Lys-[GlcNAc( 1-N)]Asn-Gly-Gly-Pro-NH 2 ,Leu-Lys-[GlcNAc( 1-4)GlcNAc ( 1-N)]Asn-Gly-Gly-Pro-NH 2 , Leu-Lys-[Man( 14)GlcNAc( 1-4)GlcNAc( 1-N)]Asn-Gly-Gly-Pro-NH 2 was carried out as follows:Rink amide-MBHA PS resin (loading: 0.81 mM/g) was applied. The first 3 aminoFig. 1. Used building blocks.98