TYROSINIUM-D-TETRAHYDROISOQUINOLINE-3-CARBOXYLATE 1.5-HYDRATE AND TYROSYL-D-TETRAHYDROISOQUINOLINE-3-CARBOXAMIDE HYDRATE

Crystals of the two dipeptide title compounds, Tyr-D-Tic, C19H20N2O4.1 .5H(2)O, and Tyr-D-Tic-NH2, C19H21N3O3.H2O, were prepared by the sitti ng-drop method. Tyr-D-Tic is orthorhombic (P2(1)2(1)2(1)) and crystall izes as a zwitterion. The asymmetric unit contains two peptide molecul es and three molecules of water. Tyr-D-Tic-NH2 crystals are monoclinic (P2(1)), the asymmetric unit containing one peptide molecule and one molecule of water. Despite some differences in packing, the conformati on of the two dipeptides is almost identical (r.m.s. deviation for non -H atoms is approximately 0.18 Angstrom).