PROBLEM TO BE SOLVED: To provide 5,6-dihydro-1H-pyridin-2-one compounds that are useful in treating hepatitis C virus.SOLUTION: The invention is directed to a 5,6-dihydro-1H-pyridin-2-one compound produced from a synthetic intermediate such as a compound represented by the following formula, and a pharmaceutical composition containing the compound that is useful in treating infections by hepatitis C virus.【課題】C型肝炎ウイルスの治療に有用な5,6-ジヒドロ-1H-ピリジン-2-オン化合物の提供。【解決手段】下記式で表される化合物等の合成中間体から生成される、5,6-ジヒドロ-1H-ピリジン-2-オン化合物類、及び、該化合物を含有する、C型肝炎ウィルスによる感染症の治療に有用な医薬組成物。【選択図】なし