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-iodosuccinimi de method employing different pathways. The efficiency of a sequential synthesis suffered from side reactions of the axial HO-3, which are t ypical of digitoxosides. These problems did not arise in a straightfor ward 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 synt hesis led to trisaccharides with different protecting group patterns. In these reactions different glycal and alcohol components were used a nd allowed to define the optimal partners in a sequential synthesis: t he two components should ideally be of comparable reactivity.