  Starting from a consistent SU(6) extension of the Weinberg-Tomozawa (WT)
meson-baryon chiral Lagrangian (Phys. Rev. D74 (2006) 034025), we study the
s-wave meson-baryon resonances in the strangeness S=-3 and negative parity
sector. Those resonances are generated by solving the Bethe-Salpeter equation
with the WT interaction used as kernel. The considered mesons are those of the
35-SU(6)-plet, which includes the pseudoscalar (PS) octet of pions and the
vector (V) nonet of the rho meson. For baryons we consider the 56-SU(6)-plet,
made of the 1/2+ octet of the nucleon and the 3/2+ decuplet of the Delta.
Quantum numbers I(J^P)=0(3/2^-) are suggested for the experimental resonances
Omega*(2250)- and Omega*(2380)-. Among other, resonances with I=1 are found,
with minimal quark content sss\bar{l}l', being s the strange quark and l, l'
any of the the light up or down quarks. A clear signal for such a pentaquark
would be a baryonic resonance with strangeness -3 and electric charge of -2 or
0, in proton charge units. We suggest looking for K- Xi- resonances with masses
around 2100 and 2240 MeV in the sector 1(1/2^-), and for pi Omega- and K- Xi*-
resonances with masses around 2260 MeV in the sector 1(3/2^-).
