  We review recent progress in calculating the twist--2 parton distribution
functions at a low normalization point in the large--$N_c$ limit, where the
nucleon can be described as a soliton of the effective chiral lagrangian. This
field-theoretic approach preserves all general requirements on the distribution
functions (positivity, normalization etc.). In particular, it allows to
calculate the polarized and unpolarized antiquark distributions at the low
normalization point.
