The Synthesis and Biological Evaluation of Some C-9 and C-10 Substituted Derivatives of the RNA Polymerase I Transcription Inhibitor CX-5461

The regio-isomeric alkynyl-substituted derivatives, 2 and 3, of the RNA Polymerase I (Pol I) transcription inhibitor CX-5461 (1) were prepared and the active one (compound 3) subjected to click reactions ([3 + 2]-cycloaddition reactions) with certain alkyl azides bearing biotin or fluorescent tags. Compounds 2 and 3, as well as four [3 + 2]-cycloadducts of the latter, were subjected to biological evaluation in a human acute myeloid leukemia cell line model. Among the six compounds tested only alkyne 3 remained active but this was less potent than parent 1.