There is an urgent need for novel therapeutics possessing new modes of action to treat tuberculosis (TB) infections. In this study we report on the synthesis and biological evaluation of a series of pyrido [2, 3, 4-kl] acridin-6-one alkaloids related to the anti-TB (MIC 0.35 μM) but cytotoxic (IC50< 0.14 μM) marine natural product ascididemin (1). The most interesting compounds identified were 21 and 24, which were found to inhibit the growth ...