L-Leucylglycine 0.67-hydrate and [(4S)-2,2-dimethyl-4-(2-methylpropyl)-5-oxoimidazolidin-3-ium-1-yl]acetate.

Crystals of L-leucylglycine (L-Leu-Gly) 0.67-hydrate, C(8)H(16)N(2)O(3)·0.67H(2)O, (I), were obtained from an aqueous solution. There are three symmetrically independent dipeptide zwitterionic molecules in (I) and they are parallel to one another. The hydrogen-bond network composed of carboxylate and amino groups and water molecules extends parallel to the ab plane. Hydrophilic regions composed of main chains and hydrophobic regions composed of the isobutyl groups of the leucyl residues are aligned alternately along the c axis. An imidazolidinone derivative was obtained from L-Leu-Gly and acetone, viz. [(4S)-2,2-dimethyl-4-(2-methylpropyl)-5-oxoimidazolidin-3-ium-1-yl]acetate, C(11)H(20)N(2)O(3), (II), and was crystallized from a methanol-acetone solution of L-Leu-Gly. The unit-cell parameters coincide with those reported previously for L-Leu-Gly dihydrate revealing that the previously reported values should be assigned to the structure of (II). One of the imidazolidine N atoms is protonated and the ring is nearly planar, except for the protonated N atom. Protonated N atoms and deprotonated carboxy groups of neighbouring molecules form hydrogen-bonded chains. The ring carbonyl group is not involved in hydrogen bonding.