β-Carbolines as Specific Inhibitors of Cyclin-Dependent Kinases

Harmine (3), 7-fluoro-1-methyl β-carboline (35) and 1-(5-methyl-imidazol-4-yl) β-carboline (41) were potent and specific inhibitors of cyclin-dependent kinases. The degree of aromaticity of the tricyclic ring and the positioning of substituents are important for inhibitory activity. While most β-carbolines inhibited CDK2 and CDK5 to the same extent, selective inhibition against CDK2 was observed in 1-(2-chlorophenyl)- (12), 1-(2-fluorophenyl)- (15), and 1-(2-chloro-5-nitrophenyl)- (28) β-carbolines.