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, C₁₉H₂₀N₂O₄.1.5H₂O, and Tyr-D-Tic NH₂, C₁₉H₂₁N₃O₃.H₂O, were prepared by the sitting drop method. Tyr-D-Tic is orthorhombic (P2₁2₁2₁), and crystallizes as a zwitterion. The asymmetric unit contains two peptide molecules and three molecules of water. Tyr-D-Tic NH₂ crystals are monoclinic (P2₁), the asymmetric unit contains one peptide molecule and one molecule of water. Despite some differences in packing, the conformation of the two dipeptides is almost identical (r.m.s. deviation for non-hydrogen atoms is approximately 0.18 Å).

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