Bobcat339 (Bobcat 339) is a novel cytosine-based TET enzyme inhibitor with IC50 of 33 uM (TET1) and 73 uM (TET2), but not DNMT3a, does not inhibit the DNA methyltransferase DNMT3a; Bobcat339 is a useful tool for investigation of epigenetics and serve as a starting point for new therapeutics that target DNA methylation and gene transcription.