| abstract |
(57) [Summary] [Structure] Formula (I) [In the formula, X 1 and X 2 do not exist respectively, or oxygen and A are OH or C 1-4 acyloxy group, B means hydrogen, or a bond together with A, X is oxygen, nitrogen, sulfur, etc., R 1 and R 2 are hydrogen, C 1-4 alkyl, etc., R 3 and R 4 represent hydrogen, C 1-4 alkyl, etc., or together represent 1,4-butylene, 1,5-pentylene, etc.], or when a salt can be formed, A therapeutic agent for heart failure comprising a pharmaceutically acceptable salt as an active ingredient. [Effect] Since these compounds have strong myocardial contractile force enhancing action and heart rate reducing action and low toxicity, they are useful as therapeutic agents for heart failure. |