Rotate Character Controller around y -axis

I am making an Endless runner game. The player objects moves forward using " Character COntroller component". Instead of moving left to right on the x-axis while running forward in z -axis, I want the controller to rotate so that the Controller can move into bends just like we have in racing games Please check the pix I attached for visualization of how i want it to move. Thanks in advance.public class PlayerBehaviour : MonoBehaviour {

 private CharacterController controller;

 public float runSpeed = 10.0f;

 public float jumpSpeed = 8.0f;

 public float sideSpeed = 10.0f;

 public float jumpForwardSpeed = 8.0f;

 public float rotSpeed = 2.0f;

 public float gravity = 20.0f;

 private Vector3 moveDirection = Vector3.zero;

 private Animator anim;



 // Use this for initialization
 void Start () {

     anim = GetComponent<Animator>();

     controller = GetComponent<CharacterController>();

 
 }
 
 // Update is called once per frame
 void Update () {

         //if we are on the ground
         if(controller.isGrounded){

         moveDirection = new Vector3(Input.GetAxisRaw("Horizontal"),0,0) * sideSpeed;

         //transform.Rotate(moveDirection * rotSpeed * Time.deltaTime);

         //transform.Rotate(moveDirection = new Vector3(Input.GetAxisRaw("Horizontal"),0,0) * rotSpeed * Time.deltaTime);

         moveDirection = transform.TransformDirection(moveDirection);

         //forward speed
         moveDirection.z = runSpeed;

         if(Input.GetMouseButtonDown(0)){ 

             //up speed
             moveDirection.y = jumpSpeed;

             moveDirection.z = jumpForwardSpeed;

             anim.Play("Jump");

         } 
                             
     }

     //if we are not on the ground
     else {
         
         moveDirection.x = Input.GetAxisRaw("Horizontal") * sideSpeed;

         moveDirection.y -= gravity * Time.deltaTime;

             }

 
     controller.Move (moveDirection * Time.deltaTime);
 

 }

[1]: /storage/temp/102283-schematics.png