ABSTRACT
Reexamination of toluene-p-sulfonic acid-catalyzed methanolysis of tertbutyl 1,2:3,4-di-O-isopropylidene-α-d-galactopyranuronate (2)1 prepared from 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose (1)2 showed that an anomeric mixture (α:β = 28:72) of methyl (methyl d-galactofuranosid)uronate (3)3,4 was formed. After column chromatography, the NMR spectra showed the material collected as 3 was pyranosides free. Benzoylation of 3 gave the corresponding 4. Acetolysis3,5 of 4 followed by treatment of the product 5 with ethanethiol and BF3·Et2O afforded methyl (ethyl 2,3,5-tri-O-benzoyl-1-thio-α,β-d-galactofuranosid)uronate 63 (α:β = 15:85, see opening scheme of this chapter). This thioglycoside donor has been used for the synthesis of several disaccharides.3
