Synthesis of glycosylated serine and threonine derivatives employing glycosidases

✍ Scribed by Kurt G. I. Nilsson; Michaela Scigelova

• Publisher: Springer Netherlands
• Year: 1994
• Tongue: English
• Weight: 356 KB
• Volume: 16
• Category: Article
• ISSN: 0141-5492
• DOI: 10.1007/bf00136469

✦ Synopsis

The galactosyl derivatives Galp-Ser(N-Boc) and Galp-Thr(N-Boc) of N-Boc-protected serine and threonine were prepared with galactose or lactose as the glycosyl donor employing 8galactosidase as the catalyst. Similarly, the mannosyl derivatives Mana-Ser(N-Boc) and Mana-Thr(N-Boc) were prepared with mannose as the glycosyl donor (equilibrium reaction) employing cc-mannosidase as the catalyst.

INTRODUCTlON

It is now widely accepted that the carbohydrate part of glycoproteins are important structures acting as specific receptor structures for proteins and cells in tivo, e.g. in inflammatory responses (Feiti, 1993) and for pathogenic bacteria and viruses in the respiratory and gastro-intestinal tract (Karlsson, 1989). The carbohydrate part in glycoproteins is bound to the protein via a glycosidic N-linkage or via a glycosidic Olinkage, e.g. a galactosyl-serine or a galactosyl-threonine linkage (Parekh, 1991).

Recently, efforts to prepare these linkages via either multi-step chemical procedures (Meldal and Bock, 1990), or via stereospecific enzymatic procedures (Johansson et.al. 1991, Cantacuzene andAttal, 1991) have been reported.

Glycosidases have been applied in a few cases. Thus, it was found that glycosylated products were obtained under equilibrium conditions, employing monosaccharide and non-modified serine or threonine in high concentrations (Johansson et al., 199'1). However, in this type of reaction, the N-glycosylation of the reducing end of the monosaccharide is a severe chemical side-reaction. Interestingly, enzymatic glycosylation