A FACILE SYNTHESIS OF 5-THIO-L-FUCOSE AND 5-THIO-D-ARABINOSE FROM D-ARABINOSE

5-Thio-L-fucopyranose tetraacetate was synthesized in 11 steps from 5- O-trityl-D-arabino-furanose or D-arabinose diethyl dithioacetal by one -carbon elongation at C-5. Highly diastereoselective addition of MeLi in ether to a ropylidene-beta-D-arabino-pentodialdo-1,4-furanose deriv ative was achieved to give the corresponding 6-deoxy-beta-D-altrofuran ose isomer in good yield. A sulfur atom was introduced at C-5 of 6-deo xy-D-altrofuranose derivatives via substitution of a 5-tosylate with K SAc in HMPA with inversion of configuration, giving 5-thio-L-fucopyran ose. A 3-O-substituted-L-fucose derivative was also prepared from 6-de oxy-beta-D-altrofuranose derivatives. 5-Thio-D-arabinopyranose tetraac etate, the 5-demethyl analog of 5-thio-L-fucose, was also synthesized from 5-O-trityl-D-arabinofuranose in 5 steps. 5-Thio-D-arabinose showe d weak inhibitory activity against a-L-fucosidase from bovine kidney ( K-i = 0.77 mM).