The natural products, capsaicin and dihydrocapsaicin, were modified at double-bond and phenolic moieties to provide twelve capsaicin and dihydrocapsaicin derivatives. The natural products and synthesized compounds were evaluated as histone deacetylase inhibitors via in vitro fluorometric assay at 500 mM concentrations. The results revealed that a methyl ester derivative and a silyl-protected dihydrocapsaicin were the best histone deacetylase inhibitors among the tested compounds with 87% and 85% inhibitions, respectively. Molecular docking experiments were conducted on the obtained compounds with the human HDAC8 enzyme. These data show a new method for providing putative histone deacetylase inhibitors from common natural products.