Effective FL, DOF, Fast Lenses

I used to have a 300mm f 2.8 lens on a 35mm film camera. I remember how nice it was for separating subjects from backgrounds.

Given that the M4/3 community lenses don't have those sorts of lenses available, not counting the adapted uses of old lenses, what lens/f/stop combo would approach the same results as the 300 f/2.8 today?

Walt