Nitrophenylgalactosides → 2-Nitrophenol

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In order to synthesize 4-O-β-D-galactopyranosyl-D-xylose, 5 g of o-nitrophenyl β-D-galactopyranoside (Gal-ONP) and 25 g of D-xylose were dissolved in 330 ml of water buffered to a pH of 7 (0.05 M KH2PO4/K2HPO4, 1 mM MgCl2, 5 mM mercaptoethanol), 80 units of E. coli β-galactosidase enzyme were added and the solution thus obtained was subjected to incubation at 37° C. in an orbital stirrer until the Gal-ONP was practically consumed (24 hours). The reaction was followed by thin layer chromatography with isopropanol/NH3(30%)/H2O (7.5/0.5/2.5) in a way similar to the one indicated in example 7. Following the methodology put forth in example 3, the reaction was stopped by heating at 100° C. for 10 minutes, it was allowed to cool and the ortho-nitrophenol formed was extracted with ethyl acetate. Celite (40 g) was added to the aqueous solution and the mixture was concentrated to dryness. The solid residue was subjected to solid-liquid extraction using a Soxhlet extractor equipped with a cellulose cartridge and using ethyl acetate (500 ml) as the solvent. After 23 hours, the resulting solid was washed with water (3×40 ml) and the aqueous solution was eluted through an active carbon-celite column. First of all, it was eluted with isopropanol/water (2%) and afterwards with isopropanol/water (4%), using a total volume of eluent of 400 ml. The enriched fractions in the 4-O-β-D-galactopyranosyl-D-xylose regioisomer were combined and concentrated to dryness. The residue was crystallized from acetone-water in a way similar to the one described in example 7, obtaining 0.44 g of pure crystalline disaccharide.

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