Molecular determinants for drug-receptors

N -( p -anisoyl)pyrrolidin-2-one in the crystalline state exhibites a cis — rans conrotatory conformation with NCO and COC ar rotational angles of 33.5° and 38.5° respectively, and the p -methoxy group situated cis to the central carbonyl bond, as shown by X-ray structure analysis. As suggested by dipole moment analysis and MMP2 molecular mechanics calculations, in solution similar conrotatory models hold for both c - and t -subconformers having the p -methoxy group cis or trans to the central carbonyl bond. INDO calculations were also carried out, indicating that both subconformers are equally stable.