Disclosed are compounds of Formula 1, and pharmaceutically acceptable salts thereof, wherein R3, R4, R5, R6, R7, R8, R9, X1 and X2 are defined in the specification. This disclosure also relates to materials and methods for preparing compounds of Formula 1, to pharmaceutical compositions which contain them, and to their use for treating diseases, disorders, and conditions associated with PHD.揭示式1化合物，及其醫藥學上可接受之鹽，其中R3、R4、R5、R6、R7、R8、R9、X1、及X2在說明書中經定義。本揭露亦關於用於製備式1化合物之材料及方法；含有該等式1化合物之醫藥組成物；及其用於治療與PHD相關聯之疾病、病症、及病狀之用途。
