The invention provides novel compounds having the general formula I: wherein R1, R2, the A ring and the B ring are as described herein, pharmaceutical 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、A環及B環如本文中所描述;包括該等化合物之醫藥組合物及使用該等化合物之方法。