Calculation of intersubstituent similarity using R-group descriptors

This paper discusses the calculation of the similarities between pairs of substituents on ring systems. An R-group descriptor characterizes the distribution of some atom-based property, such as elemental type or partial atomic charge, at increasing numbers of bonds distant from the point of substitution on the parent ring. The similarity between a pair of descriptors is then calculated by a comparison of the corresponding property vectors. Experiments with the BIOSTER database demonstrate the ability of such similarity measures to discriminate between bioisosteric and nonbioisosteric functional groups.