Abstract
The title compounds are required for the substrate specificity study on β-D-galactosidase (EC 3.2.1.23). Starting from 1, 2, 3, 2', 3', 4', 6'-hepta-O-acetyl-β-lactose, 4-O-β-D-galactopyranosyl-α-D-glucuronic acid, 6-O-methyl-α-lactose, methyl 3, 6-anhydro-β-lactoside, and 6-deoxy-α-lactose were synthesized. 1, 2, 3-Tri-O-acetyl-4-O-(2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranosyl) -β-D-xylo-hex-5-eno-pyranose (13) was also prepared by elimination of hydrogen iodide with silver fluoride in dry pyridine from 1, 2, 3, 2', 3', 4', 6'-hepta-O-acetyl-6-deoxy-6-iodo-β-lactose. In catalytic hydrogenation of 13, regardless of the catalyst, a stereospecific hydrogenation proceeded in such a way that the 6-deoxy-L-ido isomer, 1, 2, 3-tri-O-acetyl-4-O- (2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranosyl) -6-deoxy-α-L-idopyranose (14), was overwhelmingly predominant than the corresponding 6-deoxy-D-gluco isomer, 1, 2, 3-tri-O-acetyl-4-O- (2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranosyl) -6-deoxy-β-D-glucopyranose. The result was the reverse with that reported in unsaturated monosaccharide series. Deacetylation of 14 afforded 4-O-β-D-galactopyranosyl-6-deoxy-L-idopyranose as a hygroscopic powder.
