Quaternion Trouble

Hey I’m new to Unity Scripting and made this code based on a tutorial for 2d platforming to turn my character.

I want it only to do a quarter rotation Like this.

But I can’t use + or - or / or * in the code with out getting an error.
Help would be nice.
(Please Excuse the awful Bird’s eye view drawing)

	// Set rotation to the move direction	
	if (movement.direction.sqrMagnitude > 0.01)
		transform.rotation = Quaternion.Slerp (transform.rotation, Quaternion.LookRotation (-movement.direction), Time.deltaTime * movement.rotationSmoothing);

Thank You,
-Dragonos-

I’m a bit confused. Your drawings show rotating by 90 or 45 degrees, but the code would seem to be intended to rotate to a particular facing (in this case the opposite of movement.direction), which as far as I can see doesn’t have to do with your drawings.