Antitumor polycyclic acridines. 17. Synthesis and pharmaceutical profiles of pentacyclic acridinium salts designed to destabilize telomeric integrity

Palladium(O)-mediated Suzuki-Miyaura and Heck transformations have been exploited to provide examples of 8-methylquino[4,3,2-kl]acridines and 8,13-dimethylquino[4,3,2-kl]acridinium iodides bearing bulky saturated (3-acetoxy)propyl or (E)-3-(morpholin-4-yl)-3-oxopropenyl substituents variously in the 3-, 6-, or 10-positions of the pentacyclic nucleus. The pharmacological/pharmaceutical properties of four compounds (4, RHPS4), (5, IH383), (6, RHPS16), and (17, RHPS19) were measured to assess their clinical potential as DNA G-quadruplex-stabilizing/telomerase inhibitory agents. The following properties were measured: stability in tissue culture media in the presence of A549 lung and MCF-7 breast tumor cells, metabolic stability when incubated with rat liver microsomes, and rate of uptake and subcellular location in A549 and MCF-7 cells. Compound 17 was unstable in tissue culture media, failed to achieve nuclear access, and was excluded from further consideration. Of the other agents, 4 exhibited the most favorable pharmaceutical profile: the agent has appropriate stability in the presence of tumor cells and rat liver microsomes and achieves rapid ingress into cell nuclei where the putative molecular target is located.