Using a six-orientifold on top of a NS-fivebrane we construct a chiral
N = 1 SU(Nc) supersymmetric gauge theory in four dimensions with gaug
e group SU(N-c) and matter in the symmetric, antisymmetric and (anti)f
undamental representations. Anomaly cancellation is fulfilled by the r
equirement of a smooth RR 7-form charge distribution and leads us to t
he introduction of 8 half D-sixbranes ending on the NS-fivebrane. We o
btain the dual model from branes by a linking number argument. We chec
k explicitly the 't Hooft anomaly matching conditions and the map betw
een deformations in the original and the dual model.