A cell-permeable, selective SIRT1 inhibitor (IC50 = 0.7-2 µM) that reactivates p53 by inhibiting SIRT1 deacetylation activity; inhibits cell proliferation by inducing p53-dependent apoptosis in various human cancer cells (IC50s = 5.4, 51.9, 3.2, 33.9, and 85.4 µM for H460, H1299, A549, HT-29, and WI38 cells, respectively), as well as in xenograft tumors.