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), 2 mg (640 u) 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 (approximately 2 hours). Following the methodology put forth in example 3, the reaction was stopped by heating at 100° C. for 10 minutes and the ortho-nitrophenol formed was extracted with ethyl acetate. The aqueous solution was concentrated up to an approximate volume of 50 ml, filtered through glasswool and passed through the active carbon/celite column. First of all, the excess D-xylose was eluted with water and afterwards, using a fractioned gradient of EtOH/H2O (2%-10% of EtOH) the mixture of disaccharides was collected. The enriched fractions in the 4-O-β-D-galactopyranosyl-D-xylose regioisomer were combined and concentrated to a reduced volume, after which acetone was added until turbidity appeared and the mixture thus obtained was left to stand cold. The 4-O-β-D-galactopyranosyl-D-xylose was crystallized in a pure form, obtaining 970 mg, namely, a yield of 19% based on the initial Gal-ONP, whose spectral data coincided with those given for the product obtained in accordance with example 3.

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