N-Glycopeptides

With respect to application of MS to deprotection reactions, Mizuno et al.105 observed an unexpected O-acetyl cleavage in a building block of an N-glycopeptide by simple treatment with absolute methanol that had been stored over 3 A MS. When acetates from other sugars were submitted to the same conditions, similar results were obtained, whereas no O-acetyl cleavage was observed when using absolute methanol that had not been dried over 3 A MS. This deacetylation was evidently promoted by a... 

Urge, L., Otvos Jr., L., Lang, E., Wroblewski, K., Laczko, I., and Hollosi, M. (1992) Fmoc-protected, glycosylated asparagines potentially useful as reagents in the solid-phase synthesis of N-glycopeptides. Carbohydr. Res. 235, 83-93. 

N-Glycopeptides Carrying the Sialyl Lewis A Structure The regioisomeric tetrasaccharide structures sialyl Lewis A (sLea) (NeuAca(2—>3)Galp( 1 —>3) [Fuca(l— 4)]GlcNAc) and sialyl Lewis X (sLex)50 (NeuAca(2—>3)Galp( 1 —>4)... 

O- and N-Glycopeptides Synthesis of Selectively Deprotected Building Bloc... 

Jobron, L. and Hummel, G. (2000) Solid-phase synthesis of unprotected N-glycopeptide building blocks for SPOT synthesis of glycopeptides. Angew. Chem. Inti Ed. 39, 1621-1624. 

The convergent approach to N-glycopeptides was first demonstrated by Peter Lansbury et al. (Scheme 11.4) [52, 53], Condensation of an oligosaccharyl amine with the Asp side chain of a suitably protected peptide was examined in solution phase but can also be carried out in solid phase. However, the drawback of this method is that the Asp unit meant to be coupled to an oligosaccharyl amine is prone to cyclic aspartimide formation with the amide nitrogen atom of the peptide backbone. Samuel Danishefsky and coworkers examined several conditions to overcome... 

Arsequell G, Valencia G, Recent advances in the synthesis of complex N-glycopeptides, Tetrahedron Asymmetry, 10 3045-94, 1999. 

O- and N-glycopeptides Synthesis of Selectively Deprotected Building Blocks. Kunz, H. in Preparative Carbohydrate Chemistry Hanessian, S., Ed. Dekker New York, 1997, pp 265-281. 

A. L. Handlon and B. Fraser-Reid, A convergent strategy for the critical 8-linked chitobiosyl-N-glycopeptide cote, J. Am Chem. Soc. 775 3796 (1993). 

H. Kunz, H. Waldmann, and J. Marz, Synthese von N-Glycopeptid-Partialstrukturen der Verkniipfungsregion sowohl der Transmembran-Neuraminidase eines Influenza-Virus als auch des Faktors B des menschlichen Komplementsystems, Liebigs Ann. Chem. (1989) 45 9. 

Catalina, M.I. Koeleman, C.A.M. Deelder, A.M. Wuhrer, M. Electron transfer dissociation of N-glycopeptides Loss of the entire N-glycosylated asparagine side chain. Rapid Commun. Mass Spectrom 2007, 21,1053-1061. 

Applying conditions similar to the Lansbury protocol an unnatural N-glycopeptide bearing a large complex-type diantennaiy /V-glycan was convergently synthesized in the Dwek laboratory in the absence of DIPEA (Scheme 4). 

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