He briefly considered it, actually:Janacek: Anna Karenina
Vogel said:Between 5 and 29 January 1907 [Janacek] began writing an opera on [Anna Karenina] directly to a Russian text, intending it, it seems, for Russia. He may have put his hopes in that country after having been continually neglected at home. However, in spite of some interesting sketches, especially for the characters of Levin and Kitty, the work was left as a small fragment.