Nonsteroidal antiinflammatory drugs. VI. The crystal and molecular structure of (.+-.)-(2S*)-2-(4-((1S*)-2-oxocyclopentylmethyl)phenyl)propionic acid and force-field calculations.

The crystal structure of the title compound was determined by X-ray diffraction techniques. The final R index was found to be 0.072 for 1187 reflections. The torsional angles of the 2-phenylpropionic acid moiety were comparable to those in other antiinflammatory arylpropionic acids. Force-field energy calculations suggested that the α-methyl substituent to the carboxyl group restricts the rotation of the benzene ring about the Cα-phenyl bond. This restricted conformation may be related to the antiinflammatory activity.