Pyrazolidine-3,5-dione angiotensin-II receptor antagonists.

The crystal structures of three angiotensin-II receptor antagonists involving different spacer groups (CO, CONH and NHCO) between the aryl rings are presented, namely 2-[4-[(3-butyl-1,4-dioxo-2,3-diazaspiro[4.4]non-2-yl)methyl]benzoyl]benzoic acid, C(26)H(28)N(2)O(5), (I), 2-[4-[(3-butyl-1,4-dioxo-2,3-diazaspiro[4.4]non-2-yl)methyl]benzamido]benzoic acid, C(26)H(29)N(3)O(5), (II), and 2-[4-[(3-butyl-1,4-dioxo-2,3-diazaspiro[4.4]non-2-yl)methyl]anilinocarbonyl]benzoic acid monohydrate, C(26)H(29)N(3)O(5) x H(2)O, (III). The aryl rings of (II) are almost coplanar, in contrast with compounds (I) and (III). The conformation of (II) is induced by an intramolecular N-H.O hydrogen bond between the amide and carboxylic acid groups.