PreProcessor Directives have suddenly stopped working

I am working on a project that requires directives for compiling for iOS, OSX and Android and all of a sudden even the most basic #if UNITY_EDITOR is refusing to be picked up. I used MonoDevelop and i've resync'd and rebooted numerous times but the project suddenly seems out of sync with unity. I am clearly in Mac mode in the build settings but #if UNITY_STANDALONE_OSX along with all the other directives remain blanked out