transform.rotation = Quaternion.FromToRotation(transform.position, currentTarget.position);

using UnityEngine;
using System.Collections;

public class NewBehaviourScript : MonoBehaviour {

  //Цель (пункт Б)
  public Transform target;
   
  //Стартовая позиция
  private Vector3 _startPos;
  //Конечная позиция
  private Vector3 _endPos;

  private Vector3 temp;

  // Use this for initialization
  void Start () {

   //Запоминаем начальную и конечную позиции
   _startPos = transform.position;
   _endPos = target.position;
   
  }
   
  // Update is called once per frame
  void Update () {

   transform.position = Vector3.Lerp(_startPos, _endPos, Time.time/2);

               
  }

}

if (transform.position == _endPos)
{
temp =_startPos; _startPos =_endPos; _endPos = temp; Debug.Log ("Ok");    
}