Crystallization and structural studies of n-benzyloxycarbonyl-L- tyrosine-L-glycine-ethyl ester (Z-Tyr-Gly-OEt)

It is axiomatic that efficient crystal production reflects upon the quality of structure. An empirical relation for mass proportions of two solvents in crystallization of Z-Tyr-Gly-OEt shows a linear relationship. The dipeptide crystallizes in orthorhombic space group P212121, with cell parameters a=5.0680(1)Å, b=13.8650(1)Å and c=28.2630(1)Å, Z=4, Dcalc= 1.339Mg/m , μ=0.820mm-, F000=848, CuKα = 1.5418Å. The structure was solved by direct methods and final R1 and wR2 are 0.444 and 0.1276, respectively. The structure analysis reveals the trans conformation of the peptide unit with ω=-178.2(5) ̊, implying only a slight deviation from planarity. The torsion angles at glycine [φ, ψ = -84.4(7)°, 179.9(5)°] are characteristic of lefthanded poly glycine II helices. A number of N-H...O, O-H...O and C-H...O hydrogen bondings play a role in stabilizing the molecules within unit cell.