THE USE OF O-GLYCOSYL TRICHLOROACETIMIDATES IN THE SYNTHESIS OF UNSYMMETRICAL TREHALOSE ANALOGS

The coupling of O-glycosyltrichloroacetimidates with 2,3,4,6-tetra-O-b enzylated monosaccharides (gluco, manno, galacto) promoted by TMSOTf i s described, and the compositions of the crude reaction mixtures, dete rmined by C-13 NMR spectroscopy, are presented. Unsymmetrical trehalos e derivatives can be synthesized by such couplings. The versatility of the trichloroacetimidates for the synthesis of trehalose analogues ha s furthermore been demonstrated by the glycosylation of anomerically u nprotected maltose heptabenzoylate affording two trehalose-containing trisaccharides, and by the synthesis of alpha-D-galactopyranosyl alpha -D-mannopyranoside.