LARGE-SCALE SYNTHESIS OF 2 TRISACCHARIDE SPACER GLYCOSIDES CORRESPONDING TO THE BLOOD-GROUP A AND B DETERMINANTS USING THIOGLYCOSIDES AND DIMETHYL(THIOMETHYL)SULFONIUM TETRAFLUOROBORATE (DMTSB) AS PROMOTER

Two trisaccharide spacer glycosides, p-trifluoroacetamidophenylethyl 3-O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl) -2-O-(alpha-L-fucopyranosyl)-beta-D-galactopyranoside and p-trifluoroacetamidophenylethyl 2-O-(alpha-L-fucopyranosyl)-3-O -(alpha-D-galactopyranosyl)-beta-D-galactopyranoside, corresponding to the human blood group A and B determinants, were synthesized. A key fucosylgalactosyl disaccharide derivative was glycosylated with galactos-aminyl or galactosyl donors, respectively. Dimethyl(thiomethyl)sulfonium tetrafluoroborate was used for thioglycoside activation in all but one coupling reaction. The small scale procedure was further developed for use in a large scale (10-100 g final product) synthesis. Large scale syntheses of some crystalline thioglycoside building blocks are also described.