- 7-But-2-ynyl-9-(6-methoxy-pyridin-3-yl)-6-piperazin-1-yl-7,9-dihydro-purin-8-one Is a Novel Competitive and Selective Inhibitor of Dipeptidyl Peptidase IV with an Antihyperglycemic Activity. Yamazaki, K., Yasuda, N., Inoue, T., Nagakura, T., Kira, K., Shinoda, M., Saeki, T., Tanaka, I. J. Pharmacol. Exp. Ther. (2006)