Doublet-Triplet Splitting in Supersymmetric SU(6) by Missing VEV   Mechanism
  We present a realistic supersymmetric SU(6) model which implements doublet-triplet splitting by the missing vev mechanism. The model makes use of only the simplest representations, requires no fine tuning of parameters and maintains coupling constant unification as a prediction. Fermion masses also emerge in a very straightforward manner. This is the first time that the missing vev mechanism has been realized in the context of SU(6). 
Z. Chacko and R. N. Mohapatra