β-d-Galacto-pyranosyl-(1→4)-2-amino-2-de-oxy-α-d-gluco-pyran-ose hydro-chloride monohydrate (lactosamine).

The title compound, C 12 H 24 NO 10 + ·Cl - ·H 2 O, ( I ), crystallizes in the monoclinic space group P 2 1 and exists as a monohydrate of a monosubstituted ammonium chloride salt, with the reducing carbohydrate portion existing exclusively as the α-pyran-ose tautomer. The glycosidic bond geometry in ( I ) is stabilized by an intra-molecular hydrogen bond and is close to that found in crystalline α-lactose. All heteroatoms except gluco-pyran-ose ring O4 participate in an extensive hydrogen-bonding network, which propagates in all directions in the crystal structure of ( I ).