  We present a renormalizable non supersymmetric Grand Unified SO(10) model
which, at the price of a large fine tuning, is compatible with all compelling
phenomenological requirements below the unification scale and thus realizes a
minimal extension of the SM, unified in SO(10) and describing all known physics
below $M_{GUT}$. These requirements include coupling unification at a large
enough scale to be compatible with the bounds on proton decay; a Yukawa sector
in agreement with all the data on quark and lepton masses and mixings and with
leptogenesis as the origin of the baryon asymmetry of the Universe; an axion
arising from the Higgs sector of the model, suitable to solve the strong CP
problem and to account for the observed amount of Dark Matter. The above
constraints imposed by the data are very stringent and single out a particular
breaking chain with the Pati-Salam group at an intermediate scale
$M_I\sim10^{11}$ GeV.
