Some 15, 16-methylene derivatives of the aldosterone antagonist spironolactone (1) were synthesized with the purpose of increasing the antialdosterone potency and reducing the endocrinological effects of this standard compound. By introduction of a 1, a-double bond and a 15@, 16@-methylene ring in the spironolactone molecule both goals were achieved. In animal studies mespirenone (13) exhibited a threefold-greater antialdosterone potency ...