Structure and conformation of linear peptides. XIV. Structure of tert-butyloxycarbonyl-L-alanylglycine monohydrate.
The crystal structure of a dipeptide tert-butyloxycarbonyl-L-alanylglycine monohydrate (C10H18N2O5.H2O), molecular weight 264, has been determined. The crystals are monoclinic, space group P2(1), with a = 10.767(1), b = 6.317(1), c = 10.981(2)A, beta = 109.15(2) degrees, and Z = 2, Dc = 1.24 g cm-3. The structure was solved by direct methods and refined to a final R-index of 0.045 for 856 reflections (sin theta/lambda < 0.55 A-1) with I > 2 sigma. The N-terminus of the molecule blocked with the t-Boc group is uncharged and the C-terminus exists in an unionized state. The peptide unit is trans and shows slight deviations from planarity. (delta omega = 3.1 degrees). The peptide backbone is folded, with torsion angles of phi 1 = -76.0(5), psi 1 = 164.3(4), omega 1 = 176.9(5), phi 2 = 116.1(5), psi 21 = -2.8(7) and psi 22 = 177.8(4) degrees. The conformation about the urethane bond (C5-N1) is trans. The urethane group is essential planar. The conformation of the boc group is trans-trans.
Subramanian
E
E
Department of Crystallography and Biophysics, University of Madras, India.
Sahayamary
J J
JJ
D004151:Dipeptides / Q000737:chemistry*; D008968:Molecular Conformation; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D004151:Dipeptides; C081295:tert-butyloxycarbonyl-alanyl-glycine