Pharmacophoric pattern matching in files of three-dimensional chemical structures: characterization and use of...

This paper describes the use of generalized torsion angles for the screening of conformational searches in databases of three-dimensional chemical structures. A generalized torsion angle is defined as the dihedral angle between two vectors, A1-A2 and A3-A4, in which none, some, or all of the vectors A1-A2, A2-A3, and A3-A4 correspond to formal chemical bonds. The screens consist of a set of four atoms together with an associated angular range, and are identified by a statistical analysis of the frequencies of occurrence of these features in the Cambridge Structural Database. These frequencies are discussed, and the effectiveness of the screens is demonstrated by an extensive series of searches for representative pharmacophoric patterns.