Crystal Research and Technology
Cryst. Res. Technol. 36 (2001) 499 - Abstract -

M. Nilofar Nissa, S. Banumathi, D. Velmurugan, N. Ramasubbu*

Department of Crystallography and Biophysics, University of Madras, Chennai, India
*Department of Oral Pathology, New Jersey Dental School, University of Medicine and Dentistry, Newark, USA

The Crystal and Molecular Structure of tert – Butoxycarbonyl - α -aminoisobutyryl- leucyl - methyl ester

The crystal structure of a dipeptide Boc – Aib – Leu – OMe (C16H30N2O5) has been determined by X - ray diffraction analysis (CCDC # 144425). The crystals are orthorhombic, space group P212121 with a = 9.674(5), b = 13.642(2), c = 30.496(6) Å, V = 4025(2) Å3, Z = 8, Dcalc = 1.09 Mgm-3. Crystal structure was solved by direct methods and refined by full-matrix least-squares method to an R value of 0.067 (lambda=1.5418 Å) for 2389 reflections with I >= 3σ (I). The dihedral angles of the peptide backbone show that the Aib residue adopts a right handed (α R) and a left handed (α L) helical conformation in molecules A and B respectively, whereas the Leucine residue takes an extended and folded conformation in molecules A and B respectively.

Keywords: crystal structure, conformation, a-aminoisobutyric acid, leucine, folded, extended


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