Discovery of Potent, Isoform-Selective Inhibitors of Histone Deacetylase Containing Chiral Heterocyclic Capping Groups and a <i>N</i>‑(2-Aminophenyl)benzamide Binding Unit

The synthesis of a novel series of potent chiral inhibitors of histone deacetylase (HDAC) is described that contain a heterocyclic capping group and a <i>N</i>-(2-aminophenyl)­benzamide unit that binds in the active site. In vitro assays for the inhibition of HDAC1, HDAC2, HDAC3-NCoR1, and HDAC8 by the <i>N</i>-(2-aminophenyl)­benzamide <b>24a</b> gave respective IC₅₀ values of 930, 85, 12, and 4100 nM, exhibiting class I selectivity and potent inhibition of HDAC3-NCoR1. Both imidazolinone and thiazoline rings are shown to be effective replacements for the pyrimidine ring present in many other 2-(aminophenyl)­benzamides previously reported, an example of each ring system at 1 μM causing an increase in histone H3K9 acetylation in the human cell lines Jurkat and HeLa and an increase in cell death consistent with induction of apoptosis. Inhibition of the growth of MCF-7, A549, DU145, and HCT116 cell lines by <b>24a</b> was observed, with respective IC₅₀ values of 5.4, 5.8, 6.4, and 2.2 mM