A compound is represented by Structural Formula (I):or a pharmaceutically acceptable salt thereof, wherein the variables of Structural Formula (I) are as described in the specification and the claims. A pharmaceutical composition comprises a compound represented by Structural Formula (I) or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier of excipient. A method of treating a HCV infection in a subject comprises administering to the subject a therapeutically effective amount of a compound represented by Structural Formula (I) or a pharmaceutically acceptable salt thereof. A method of inhibiting or reducing the activity of HCV polymerase in a subject or in a biological in vitro sample comprises administering to the subject or to the sample a therapeutically effective amount of a compound represented by Structural Formula (I) or a pharmaceutically acceptable salt thereof.本發明提供一種由結構式(I)表示之化合物:或其醫藥學上可接受之鹽,其中結構式(I)之變數如說明書及申請專利範圍中所述。醫藥組合物包含由結構式(I)表示之化合物或其醫藥學上可接受之鹽,及醫藥學上可接受之載劑或賦形劑。一種治療個體之HCV感染的方法包含向該個體投與治療有效量之由結構式(I)表示之化合物或其醫藥學上可接受之鹽。一種抑制或降低個體或活體外生物樣品中之HCV聚合酶之活性的方法包含向該個體或該樣品投與治療有效量之由結構式(I)表示之化合物或其醫藥學上可接受之鹽。(無元件符號說明)