Crystal and molecular structure of perindopril erbumine salt

The crystal structure of perindopril (2S,3aS,7aS)-1-[(2S)-2-[[(2S)-1-ethoxy-1-oxopentan-2-yl]amino]propanoyl]-2,3,3a,4,5,6,7,7a-octahydroindole-2-carboxylic acid) erbumine salt C23H43N3O5, angiotensinconverting enzyme inhibitor, was determined from single-crystal X-ray diffraction data. The compound crystallizes in the triclinic, non-centrosymetric space group P1, with unit cell dimensions a = 6.575(3), b = 12.165(5), c = 16.988(8) angstrom and alpha = 97.153(4), beta = 94.417(4), gamma = 90.349(4)degrees, Z = 2. The structure was refined by full matrix least squares methods to R = 0.037. In the solid state ionized molecules of perindopril and erbumine are linked together forming a complex via O center dot center dot center dot HN+ hydrogen bonds between the positively charged amino groups of the erbuminium cations and oxygen atoms of the perindopril carboxylate groups. Intermolecular N-H center dot center dot center dot O and C-H center dot center dot center dot O contacts seem to be effective in the stabilization of the structure, resulting in the formation of a three-dimensional network. The gas-phase structure of perindopril-erbumine complex was optimized by the HF/6-31G(d) and Becke3LYP/6-31G(d) methods. The conformational behavior of this salt in water was examined using the CPCM and Onsager models. In both the gas phase and water solution the perindopril erbumine will exist in prevailing triclinic form. (C) 2011 Elsevier B.V. All rights reserved.