Glycosylation glycopeptide synthesis

In fact, other studies have shown that TMSOTf catalyzes the glycosylation of a silylated acceptor with a silylated hemiacetal donor [49]. Nudel man s procedure was applied to the synthesis [1-glucuronide 30, isolated in 57% yield. Kiyoi and Kondo have applied the TMSOTf activation protocol to protected L-fucose hemiacetal donors for glycopeptide synthesis and obtained glycopeptide fragment 31 in 74% yield (a p, 20 1) [50], Posner and Bull have developed a procedure that uses excess TMSOTf in the presence of molecular sieves (SYLOSIV A4) to synthesize various l.l -linked disaccharides such as the galactopyranose dimer 32 [51,52]. 

The high specificity and stereoselectivity of enzymes, as well as the mild conditions under which they react, make enzyme-catalyzed reactions versatile tools in the synthesis of glycoconjugates. In some instances, an enzymic one-step transformation affords higher yields then the conventional and more-complex chemical synthesis. The application of enzymes in glycopeptide synthesis is under active development for selective deprotection and glycosylation purposes. 

Sequential solid-phase glycopeptide synthesis using glycosylated amino acid building blocks... 

Scheme 28 Synthesis of Glycosylated Hydroxylysine Building Blocks and Solid-Phase Glycopeptide Synthesis Using the Glycal[3501...

A major progress in glycopeptide synthesis was achieved when it was demonstrated that the NH2-terminal 9-fiuorenylmethoxycarbonyl (Fmoc) group can be selectively removed from glycopeptides using the weak base morpholine (pKa 8.3). This holds true for O-glycosyl serine and threonine esters, which are sensitive to base-catalyzed P-elimination of the carbohydrate [10]. 

Glycosylation of a Threonine Derivative Suitable for Glycopeptide Synthesis [55]... 

Seitz, O. (2000) Glycopeptide synthesis and the effects of glycosylation on protein structure and activity. Chem. BioChem. 1, 214-246. 

Arsequell, G. and Valencia, G. (1997) 0-Glycosyl a-amino acids as building blocks for glycopeptide synthesis. Tetrahedron Asymmetry 8, 2839-2876. 

Salvador, L., Elofsson, M., and Kihlberg, J. (1995) Preparation of building blocks for glycopeptide synthesis by glycosylation of Fmoc amino acids having unprotected carboxyl groups. Tetrahedron Lett. 51, 5643-5656. 

Allyl, benzyl, phenylacyl and f-butyl esters are commonly used for protection of the carboxyl group. These esters can be removed without affecting the Fmoc group, and the resulting deprotected glycosylated amino acids can be used in glycopeptide synthesis. 

Jansson AM, Jensen KJ, Meldal M, Lomako J, Lomako WM, Olsen CE, Bock K, Solid-phase glycopeptide synthesis of tyrosine-glycosylated glycogenin fragments as substrates for glucosylation by glycogenin, J. Chem. Soc. Perkin. Trans., 11001, 1996. 

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