A novel parameter (S1) for three-dimensional shape similarity between groups: correlation with molecular recognition and biological activity

A new parameter (S1) representing the three-dimensional shape similarity between groups is defined as the degree of a maximal overlap between a pair of groups located within a three-dimensional grid. S1, which ranges from 0 to 1, has been calculated for 105 pairs of groups including straight-chain (C1–C6), branched (C4–C6), and cyclic alkyl groups, and a phenyl group. A close relationship has been found to exist between S1 and (i) the degree of the discrimination between groups by a given group in the oxidation of a pair of associating thiols and (ii) relative biological activity (i.e., effect on cat blood, pressure) of a homologous series of benzilic esters.