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S Köpper

Publications and source records attributed to S Köpper.

5 recordsLinked to original sources

Rare sugars and sugar-based synthons by chemo-enzymatic synthesis.

The unique catalytic potential of the fungal enzyme pyranose oxidase was demonstrated by preparative conversions of a variety of carbohydrates, and by extensive chemical characterization of the reaction products with NMR spectroscopy. The studies revealed that POx not only oxidizes most substrates very efficiently but also that POx possesses a glycosyl-transfer potential, producing disaccharides from beta-glycosides of higher alcohols. Although most substrates are oxidized by POx at the C-2 position, several substrates are converted into the 3-keto-derivatives. On the basis of these products, strategies are developed for the convenient production of sugar-derived synthons, rare sugars and fine chemicals by combining biotechnical and chemical methods.

Journal Article↗

One-pot-synthesis of alpha-linked deoxy sugar trisaccharides.

Various alpha-linked 2,6-dideoxy-ribo-trisaccharides, models for part of the antibiotic kijanimicin, were synthesised by the N-iodosuccinimide method employing different pathways. The efficiency of a sequential synthesis suffered from side reactions of the axial HO-3, which are typical of digitoxosides. These problems did not arise in a straightforward polymerisation, performed as a one-pot-procedure. It afforded the trisaccharide directly from the monosaccharide precursor in 30% yield. A combination of the oligomerisation pathway and the sequential synthesis led to trisaccharides with different protecting group patterns. In these reactions different glycal and alcohol components were used and allowed to define the optimal partners in a sequential synthesis: the two components should ideally be of comparable reactivity.

Carbohydrate Conformation↗

Polymers having (1----4)- and (1----6)-linked alpha-D-glucopyranosyl groups as acceptors in the glycogen synthase reaction.

Insoluble, light-sensitive polymers linked to maltose, maltotriose, a glycogen-branch point trisaccharide, and panose were synthesized and served in a comparative study as acceptors in the glycogen synthase (UDP-D-glucose:glycogen 4-alpha-D-glucosyltransferase, EC 2.4.1.11) reaction. The highest transfer rate was observed with the maltotrio polymer. Extending the acceptor linearly with (1----4)-linked alpha-D-glucopyranosyl residues improved the transfer, whereas (1----6)-linked alpha-D-glucopyranosyl branches decreased it.

Carbohydrate Sequence↗