β-d-Galactopyranosyl-thiohydroximates and d-galactopyranosylidene-spiro-oxathiazoles: synthesis and enzymatic evaluation against E. coli d-galactosidase

By reaction with arylhydroximoyl chlorides, 2,3,4,6-tetra-O-acetyl-1-thio-β-d-galactopyranose was converted to the corresponding β-d-galactopyranosyl-thiohydroximates, which gave predominantly (1S)-d-galactopyranosylidene-spiro-oxathiazoles on illumination in the presence of NBS. Conventional O-deacetylation of both thiohydroximates and oxathiazoles gave weak inhibitors of E. coli d-galactosidase (Ki 1.1–11.1 mM).