Based on the results at a single dose, we decided to test the enzymatic inhibitory activity of DNMT1, DNMT3A, and DNMT3B of the two most active compounds 12 and 13 in dose-response assays. Results, summarized in Figure and detailed in Table in the Supporting Information, indicated that 12 is a potent nanomolar and selective inhibitor of DNMT1 (IC 50 = 30 nM), with higher inhibition of DNMT3A (IC 50 = 4,870 nM) and no enzymatic inhibition of DNMT3B (IC 50 > 100,000 nM).