Synthesis and skeletal muscle relaxant activity of 3- (aminoacyl)-1-[[[5- (substituted phenyl)-2- furanyl]methylene]amino]-2,4-imidazolidinediones

A series of 3-(aminoacyl)-1-[[[5-(substituted phenyl)-2-furanyl]methylene]amino]-2,4-imidazolidinediones was synthesized and evaluated for skeletal muscle relaxant activity. All compounds were active by the intravenous route, and nine of 11 were active orally. One compound was very active when evaluated by the mouse Straub tail and rotarod tests; its efficacy index (ED₅₀ rotarod/ED₅₀ Straub tail) was 2.0, while its therapeutic index (LD₅₀/ED₅₀ Straub tail) was >225.