  A large-S approach to the description of chiral phases in frustrated
antiferromagnetic spin-S chains with easy-plane anisotropy is proposed. The
approach is valid in the vicinity of the classical Lifshitz point j=1/4, where
j is the relative strength of the frustrating next-nearest-neighbor coupling.
The effective theory turns out to be the nonlinear sigma-model with the
additional fourth-order term in spatial derivatives. The topological term
persists for j>1/4, which leads to disappearance of the chiral gapped phase for
half-integer S, in accordance with the recent numerical results.
