[Structure-activity relationships of etozolin, a novel diuretic (author's transl)].

Selection of a structurally confined group of diuretics out of 2-methylenethiazolidones-(4), a new class of compounds, and related heterocycles with partly choleretic properties is described. The physico-chemical parameters of ethyl (Z)-(3-methyl-4-oxo-5-piperidino-thiazolidin-2-ylidene) acetate (3; etozolin, Gö 687, Elkapin), which has been selected for therapeutic use, are discussed with respect to its close structural relation to the choleretic piprozoline (2). Both the spectroscopic results and the anomalous thermodynamic data of 2, 3 and the homologous compounds 4 and 5 demonstrate a structural specificity of 3 unknown up to now with diuretics.