I am looking for a feat that in some way resembles Step Up from Pathfinder:
Step Up (Combat)
You can close the distance when a foe tries to move away.
Prerequisite: Base attack bonus +1.
Benefit: Whenever an adjacent foe attempts to take a 5-foot step away from you, you may also make a 5-foot step as an immediate action so long as you end up adjacent to the foe that triggered this ability. If you take this step, you cannot take a 5-foot step during your next turn. If you take an action to move during your next turn, subtract 5 feet from your total movement.
My goal is to prevent a caster to take a 5-foot step away from me while we are engaged in melee, in this way he/she is forced to cast defensively.
I understand that a weapon with reach could easily do the trick, but I can not consider this options.
So, is there any Feat or Class Feature that could help?