Synthesis of 3,8,9-trisubstituted-1,7,9-triaza-fluorene-6-carboxylic acid derivatives as a new class of insulin secretagogues Original Research Article

β-Carbolines stimulate insulin secretion in a glucose-dependent manner, probably by acting on I3-binding site. Knowing the in vitro glucose-dependent insulinotropic potential of β-carbolines, in this project, three series of substituted-triaza-fluorene-6-carboxylic acids (5a–v, 6a–t, and 7a–t) were designed (analogs of β-carboline) as a new class of insulinotropic agents. The in vitro glucose-dependent insulinotropic activities of test compounds were evaluated using RIN5F assay. Interestingly, with respect to the control, test compounds showed concentration-dependent insulin release, only in presence of glucose load (16.7 mmol). Some of the test compounds from each series were found to be equipotent to standard compound (Harmane), indicating that the pyridine ring systems of substituted-triaza-fluorenes act as bioisosteres of benzene ring in β-carbolines.