The present invention provides compounds of the formula below: where A, X and R1-R6 are as described herein, a pharmaceutical salt thereof, and a pharmaceutical composition containing this compound; methods of treating pain associated with osteoarthritis using one of the compounds or a pharmaceutically acceptable salt thereof, and processes for preparing the compounds.本發明提供下式化合物:其中A、X及R1-R6係如本文所述,其醫藥鹽,及含有此化合物之醫藥組合物;使用該等化合物之一或其醫藥上可接受鹽治療與骨關節炎相關之疼痛之方法,及製備該等化合物之方法。