The invention provides compounds having the general formula I: and pharmaceutically acceptable salts thereof, wherein the variables RA, RAA, subscipt n, ring A, X2, L, subscript m, X1, R1, R2, R3, R4, R5, and RN have the meaning as described herein, and compositions containing such compounds and methods for using such compounds and compositions.本發明提供具有通式I之化合物:及其醫藥學上可接受之鹽,其中變數RA、RAA、下標n、環A、X2、L、下標m、X1、R1、R2、R3、R4、R5及RN具有如本文所述之含義,以及含有該等化合物之組合物及使用該等化合物與組合物之方法。