The present invention relates to compounds of formula I
and the pharmaceutically acceptable salts and esters thereof wherein X1, X2, R1, R2, R3, R4, R5 and R6 are defined as in claim. The compounds exhibit activity as anticancer agents.
本发明涉及式 I 的化合物
及其药学上可接受的盐和
酯,其中 X1、X2、R1、R2、R3、R4、R5 和 R6 的定义如权利要求所述。这些化合物具有抗癌活性。