  Since b quark mass is not asymptotically large, chirally enhanced corrections
which arise from twist-3 wave functions may be important in B decays. We thus
evaluate the hadronic matrix elements with the emitted meson described by
leading twist and twist-3 distribution amplitudes $\Phi_p(x)$. After summing
over the four "vertex correction" diagrams, we obtain the results with infrared
finiteness which shows that chirally enhanced corrections arise from
$\Phi_p(x)$ can be consistently included in QCD factorization. We also briefly
discuss the contributions from "hard spectator" diagrams.
