The present invention provides a compound of formula I
1
or a pharmaceutically acceptable salt thereof wherein R
1
and R
2
are as defined in the specification. The compounds are useful for the treatment of viral infections.
本发明提供了一种具有
化学式I1的化合物或其药用可接受的盐,其中R1和R2如规范中定义。这些化合物对于治疗病毒感染是有用的。