X-RAY STRUCTURAL CHARACTERIZATION OF DISORDERED EPIFRIEDELIN-3-OL AND FRIEDELIN -3-ONE

Auphatham Phothikanith; Kenneth J. Haller

Authors

Auphatham Phothikanith School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 Thailand
Kenneth J. Haller School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000 Thailand

Keywords:

X-ray crystallography, structure correlation, disordered structure, natural product

Abstract

Structure correlation to examine the hybridization of carbon C3 in friedalane and oleanane triterpene structures revealed one anomalous compound in the structure database. Redetermination of the structure of the anomalous compound clearly demonstrates that the oxygen at C3 is disordered. The major component of the structure is epifriedelin-3-ol with a refined occupancy of 0.680(3). The minor component is friedelin-3-one, the only difference being the ketone at C3. The bond lengths of the disordered components are d[C-O] = 1.426(5) and d[C=O] = 1.251(6) , giving occupancy weighted averages of 1.370 and 341.4 for d[C-O], nearly the same as the 1.33 7.33 A ฬ and 343.1 values reported in the anomalous structure. Refinement converged with a conventional R of 0.0563 and the highest peak on the electron density difference map of 0.22(3) e -3.

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