And to provide an effective compounds for disease prevention [challenge] thrombopoietin receptor activation effect is enabled, improvement or treatment. [SOLUTION] Equation (1) tautomers compound represented by of the compound (as defined in the text 3, R 4 R in the formula 1, R 2, R is) a pharmaceutically prodrug or salt, or a solvate thereof may be acceptable manner. [Formula 1]【課題】トロンボポエチンレセプター活性化作用が有効な疾患の予防、治療又は改善に有効な化合物類を提供する。【解決手段】式(1)(式中のR1、R2、R3、R4は、本文中に定義される)で表わされる化合物、該化合物の互変異性体、プロドラッグ若しくはその医薬的に許容され得る塩又はそれらの溶媒和物。【化1】
