WORKS:
 postRegisterDev(regdata: devRegClass): Observable<{ data: devRegClass }> {

    let token = Observable.from(this.userAccess_token())

    return token.switchMap(access_token => {
      let postHeaders = new HttpHeaders({
        Authorization: access_token
      })

      return this.http.post<{ data: devRegClass }>(AppSettings.REGISTER_DEV_URL, regdata, { headers: postHeaders }).catch(this.handleError);
    })
  }

NO NO NO WORKS:
 postRegisterDev(regdata: devRegClass): Observable<{ data: devRegClass }> {

    let token = Observable.from(this.userAccess_token())

    return token.Map(access_token => {
      let postHeaders = new HttpHeaders({
        Authorization: access_token
      })

      return this.http.post<{ data: devRegClass }>(AppSettings.REGISTER_DEV_URL, regdata, { headers: postHeaders }).catch(this.handleError);
    })
  }