PROBLEM TO BE SOLVED: To provide a compound that is a selective agonist of Cannabinoid Receptor 2.SOLUTION: This invention relates to: a pyrazine derivative expressed by formula (I)； or a pharmaceutically acceptable salt or ester thereof. The compound is used for the therapy or prophylaxis of pain, atherosclerosis, regulation of bone mass, inflammation, ischemia, reperfusion injury, systemic fibrosis, liver fibrosis, lung fibrosis, kidney fibrosis, chronic allograft nephropathy, congestive heart failure, myocardial infarction, systemic sclerosis, glomerulopathy, thermal injury, burning, hypertrophic scars, keloids, gingivitis, pyrexia, liver cirrhosis or tumors.SELECTED DRAWING: None【課題】カンナビノイド受容体２の選択的アゴニストである化合物の提供。【解決手段】式（Ｉ）で表されるピラジン誘導体又はその薬学的に許容される塩若しくはエステル。疼痛、アテローム性動脈硬化症、骨量の制御、炎症、虚血、再灌流傷害、全身性線維症、肝線維症、肺線維症、腎線維症、慢性移植腎症、鬱血性心不全、心筋梗塞、全身性硬化症、糸球体腎症、熱傷、火傷、肥厚性瘢痕、ケロイド、歯肉炎、発熱、肝硬変又は腫瘍の治療又は予防のための、前記化合物。【選択図】なし
