Structure, histone deacetylase, and antiprotozoal activities of apicidins B and C, congeners of apicidin with proline and valine substitutions.

[structure: see text]. Isolation and structure elucidation of two novel cyclic tetrapeptides that show a variety of potent antiprotozoal activities by reversibly inhibiting HDAC have been reported. These are the new members of a unique family of cyclic tetrapeptides that do not require the electrophilic alpha-epoxyketone moiety of HC-toxin, trapoxin A, or chlamydocin for their potent activities against HDAC and the malarial parasite.