Design, synthesis, and pharmacological evaluation of N-bicyclo-5-chloro-1H-indole-2-carboxamide derivatives as potent glycogen phosphorylase inhibitors Original Research Article

As a result of the various N-bicyclo-5-chloro-1H-indole-2-carboxamide derivatives with a hydroxy moiety synthesized in an effort to discover novel glycogen phosphorylase (GP) inhibitors, 5-chloro-N-(5-hydroxy-5,6,7,8-tetrahydronaphthalen-2-yl)-1H-indole-2-carboxamide (5b) was found to have potent inhibitory activity. The introduction of fluorine atoms both at a position adjacent to the hydroxy group and in the central benzene moiety lead to the optically active derivative 5-chloro-N-[(5R)-1,3,6,6-tetrafluoro-5-hydroxy-5,6,7,8-tetrahydronaphthalen-2-yl]-1H-indole-2-carboxamide (25eα, which was the most potent compound in this series (IC50 = 0.020 μM). This compound inhibited glucagon-induced glucose output in cultured primary hepatocytes with an IC50 value of 0.69 μM, and showed oral hypoglycemic activity in diabetic db/db mice at 10 mg/kg. Compound 25eα also had an excellent pharmacokinetic profile, with high oral bioavailability and a long plasma half-life, in male SD rats. The binding mode of 25eα to this molecule and the role of fluorine atoms in that binding were speculated in an enzyme docking study.