Design, synthesis and biological evaluation of selective histone deacetylase 6 (HDAC6) inhibitors bearing benzoindazole or pyrazoloindazole scaffold as surface recognition motif.

A series of compounds were designed and synthesized based on the compound 11i bearing phenylpyrazole scaffold with histone deacetylase 6 (HDAC6) inhibitory activity. Most of the compounds showed considerable inhibitory activity against HDAC6 and compound A16 with good inhibitory activity was found therein. We further found that A16 had an inhibitory effect on inflammatory mediators (NO, TNF-α, IL-6) involved in inflammatory response and neuroendocrine regulation. In addition, A16 has a certain neuroprotective effect on PC12 cells injured by hydrogen peroxide. Acute toxicity assay showed that the LD of A16 was 274.47 mg/kg in mouse model. Furthermore, A16 displayed good stability properties in microsomes and plasma.