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Crystal and molecular structure and conformational analysis of (1RS, 2SR)-1-[N-(tert-butoxycarbonyl)amino]-2-hydroxymethylcyclopropane-1-carboxylic acid

The crystal structure of (1RS, 2SR)-1-[N-(tert-butoxycarbonyl)amino]-2-hydroxymethylcyclopropane-1-carboxylic acid, a derivative of 1-aminocyclopropanecarboxylic acid (Acc), was determined by X-ray analysis. The molecule possesses the Z-configuration of the cyclopropane ring, a disordered carboxylic group, and a trans conformation of peptide bond. Intermolecular hydrogen bonds form R22(8) and R22(10) dimers and infinite chains along the b-axis. Mutually connected molecules are in ab-plane separated by hydrophobic channels formed between tert-butil groups and adjacent molecules. Conformational analysis using molecular-mechanics method, supported by the overlapping spheres method for finding the low-energy conformations, showed thet the conformation observed in crystal state had 2.8 kj mol-1 higher conformational energythan the lowest conformation. Calculations for the dimer consisting of x, y, z and x, y-1, z molecule showed a high correlation between the reproduction of crystal structure and similaritiy of its monomer units, which suggests that the symmetry of the dimer is not caused by crystal packing.

2 ; 3-methanoamino acids ; molecular mechanics ; global optimisation ; overlappling spheres method ; single crystal X-ray analysis

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