The present invention provides a compound which has a PDHK-inhibiting activity and is useful for the treatment or prevention of diabetes (type 1 diabetes, type 2 diabetes, etc.), insulin resistance syndrome, metabolic syndrome, hyperglycemia, hyperlactatemia, diabetes complications (diabetic neuropathy, diabetic retinopathy, diabetic nephropathy, cataract, etc.), heart failure (acute heart failure, chronic heart failure), cardiomyopathy, myocardial ischemia, myocardial infarction, angina pectoris, dyslipidemia, atherosclerosis, peripheral arterial disease, intermittent claudication, chronic obstructive pulmonary disease, brain ischemia, stroke, mitochondrial disease, mitochondrial encephalomyopathy, cancer, pulmonary hypertension or Alzheimer's disease. The present invention relates to a compound represented by formula [I-a] or [II] or a pharmaceutically acceptable salt thereof. [In the formulae, each symbol is as defined in the description].本發明為提供一種化合物，其係具有PDHK阻礙活性，其係有用於糖尿病(第1型糖尿病、第2型糖尿病等)、胰島素抗性症候群、代謝症候群、高血糖症、高乳酸血症、糖尿病合併症(糖尿病性神經障礙、糖尿病性視網膜病變、糖尿病性腎症、白內障等)、心臟衰竭(急性心臟衰竭、慢性心臟衰竭)、心臟病變、心肌缺氧症、心肌梗塞、狹心症、血脂異常症、動脈粥瘤性硬化症、末梢動脈疾病、間歇性跛行、慢性閉鎖性肺疾病、腦部缺血症、中風、粒線體病、粒線體腦肌病、癌、肺高血壓症或阿茲海默症之治療或預防。本發明為關於一種式[I-a]或式[II]之化合物，或其製藥上容許之鹽。[式中之各記號與說明書記載相同。]
