Animation rotates in wrong way

Hy,
I have a scene with a 3d Cube which have 3 states of animation. The first is the Idle, and the two other which rotate the cube. one anim rotates it to 90 degrees and other to -90 degrees.
My problem is that when I set the second animation (-90 degrees) unity automatically fix it to 270 degrees which causes it to rotate in the opposite way, and make a long way too.
Is there any way to force unity to take the Cube to -90 degrees instead of 270, or any other way to Make the rotation in the way I want it to be?
Thanks.

Try mirroring the animation that rotates the cube 90 degrees. There should be an option for that on the import settings.