Preprocessor for Unity version higher than 4.3

I need a way to define a preprocessor in C# that tell if the Unity version is higher than 4.3. In C++, it would be easy with .h but I’m not sure it’s possible in C#. And I need that in the editor

ex:

#if UNITY_VERSION > UNITY_4_3
#define UNITY2D
#endif

#if UNITY2D
//do 2d stuff
#endif

#if UNITY_4_0 || UNITY_4_0_1 || UNITY_4_1 || UNITY_4_2
#define PRE_UNITY_4_3
#endif

#if !PRE_UNITY_4_3
// do 2D stuff
#endif