The invention provides novel compounds having the general formula (I) wherein R1, R2, A1and A2 are as described herein, compositions including the compounds and methods of using the compounds.本發明提供具有通式(I)之新穎化合物其中R1、R2、A1及A2係如本文中所述,包括該等化合物之組合物及使用該等化合物之方法。