Disclosed herein are compounds of Formula (I), and pharmaceutically acceptable salts thereof, wherein R1-R8have any of the meanings defined herein. Also disclosed are pharmaceutical compositions comprising compounds of Formula (I) and methods of using the same.本文揭露了具有化學式 (I) 之化合物, 及其藥學上可接受的鹽,其中R1-R8具有本文定義的含義中的任一者。還揭露了包含具有化學式 (I) 之化合物的醫藥組成物及其使用方法。