You could use Turret behaviour combined with LOS.
The LOS looks if the player can be seen, accounting for obstacles. Not seen = dissable the turret.
The turret takes care of the angle (only rotates when the player is in range), take care of choosing the moment that it will run to the player (when it has a target), knows at wich angle to move towards the player.
Or LOS combined with Pahfinding.
Attach a invisible object to the nose of the player. Give it a high Cost. Now the Pathfinder wil prefer the back of the player for aproaching.