Solubility and crystal structure of N-(1-deoxy-β-d-fructopyranos-1-yl)-l-histidine monohydrate (‘d-fructose-l-histidine’)

Within a set of food-related Amadori compounds, crystalline N-(1-deoxy-β-d-fructopyranos-1-yl)-l-histidine monohydrate (Fru-l-His × H2O) has an unusually low solubility in water, which we determined as 0.21 g/100 g at 25 °C. The majority of the other fructose-amino acid conjugates have solubilities exceeding 100 g/100 g in water at this temperature. We report the crystal structure data on Fru-l-His × H2O. The conformation of the carbohydrate is the normal 2C5 pyranose chair. Bond lengths and valence angles compare well with the average values from a number of pyranose structures. All hydroxyl and carboxyl oxygen atoms, all nitrogen atoms and the water molecule are involved in an extensive hydrogen bonding, which forms a network of infinite chains with small antidromic rings.