rxJs & angular 4 & restangular: stack errorInterceptors

In my angular 4 app I'm using ngx-restangular to handle all server calls. It returns observable as result, and this module has hooks to handle errors (like 401 etc).

But from documentation, i can handle 403 (401) so:

  RestangularProvider.addErrorInterceptor((response, subject, responseHandler) => {
    if (response.status === 403) {

      refreshAccesstoken()
      .switchMap(refreshAccesstokenResponse => {
        //If you want to change request or make with it some actions and give the request to the repeatRequest func.
        //Or you can live it empty and request will be the same.

        // update Authorization header
        response.request.headers.set('Authorization', 'Bearer ' + refreshAccesstokenResponse)

        return response.repeatRequest(response.request);
      })
      .subscribe(
        res => responseHandler(res),
        err => subject.error(err)
      );

      return false; // error handled
    }
    return true; // error not handled
  });

and this is good for one request, which has broken with 403 error. how can i stack this calls using rxJs? Becouse now, for example, i have 3 requests, which have 403 and for each this broken request I'm refreshing token - this is not so good, i have to update my token and then repeat all my broken requests. How can I achive this using Observables?

In angular 1 it was pretty easy:

Restangular.setErrorInterceptor(function (response, deferred, responseHandler) {
  if (response.status == 403) {
    // send only one request if multiple errors exist
    if (!refreshingIsInProgress) {
      refreshingIsInProgress = AppApi.refreshAccessToken(); // Returns promise
    }


    $q.when(refreshingIsInProgress, function () {
      refreshingIsInProgress = null;

      setHeaders(response.config.headers);

      // repeat request with error
      $http(response.config).then(responseHandler, deferred);
    }, function () {
      refreshingIsInProgress = null;

      $state.go('auth');
    });

    return false; // stop the promise chain
  }

  return true;
});

And all was working like a charm. But I'm new to rxJs & angular 4 and I don't have any idea how to achive this with observables and angular 4. Maybe somebody have an idea?

upd! here is my refreshAccesstoken method

const refreshAccesstoken = function () {
  const refreshToken = http.post(environment.apiURL + `/token/refresh`,
    {refreshToken: 'someToken'});
  return refreshToken;
};