Trailing Edge Unification via an Intermediate Pati-Salam Group
  We demonstrate to two-loop order that an intermediate symmetrically embedded Pati-Salam $SU(2)_L \times SU(2)_R \times SU(4)$ level of symmetry is all that is necessary to accommodate empirical values of $\alpha(M_z), \alpha_s(M_z)$ and $\sin^2\theta_w(M_z)$ within a grand unification context but with a high (10^{14} GeV) intermediate mass scale and with a concomitant higher GUT scale. 
V. Elias, T.G. Steele