Isoxazol-5(4H)one derivatives as PTP1B inhibitors showing an anti-obesity effect

In developing inhibitors of therapeutic target enzymes, significant time and effort are committed to the preparation of large numbers of compounds. In an effort to develop a potent inhibitor of protein tyrosine phosphatase (PTP) 1B as an anti-obesity and/or anti-diabetic agent, we constructed an isoxazolone chemical library by using a simplified procedure that circumvents tedious workup and purification steps. The 10×7 isoxazolone derivatives were synthesized by coupling the two halves of the target compounds. When mixed and heated in test tubes, the precursors produced the reaction products as precipitates. After brief washing, the products were pure enough to be used for enzymatic experiments. With the precursors for the coupling reactions prepared, the 10×7 library compounds could be prepared in a day by using the present protocol. The library compounds thus obtained were examined for their inhibitory activities against PTP1B. Among them, compound C3 was the most potent inhibitor of PTP1B with an IC(50) of 2.3 μM. The in vivo effect of C3 was also examined in an obesity-prone mouse strain. Diet-induced obese (DIO)/diabetic mice were divided into two groups and each group was fed a high-fat diet (HFD) or HFD+C3 for four weeks. The group of C3-fed mice gained significantly less weight relative to the HFD-fed control group during the four weeks of the drug feeding period. In contrast to the anti-obesity effect of C3, no difference was observed in the glycemic control of the HFD and HFD+C3 mice groups.