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Synthesis, in‐vitro Cytotoxicity, and a Preliminary Structure‐Activity Relationship Investigation of Pyrimido[4,5‐c]quinolin‐1(2H)‐ones

As part of our ongoing research effort to develop new antimitotic agents based on the recently reported pyrimido[4,5‐c]quinoline‐1(2H)‐one ring skeleton, we were interested in identifying structural elements that contribute to the cytotoxicity of this class of compounds. The effect of several quinoline‐ring substituents was examined and the new compounds were evaluated in vitro for cytotoxicity against three human cancer cell lines namely, lung fibrosarcoma HT‐1080, colon adenocarcinoma HT‐29, and breast carcinoma MDA‐MB‐231. Most of the compounds showed cytotoxic activity in the low micromolar and sub‐micromolar range. Structure‐activity relationship information revealed that a combination of electronic and steric factors may be involved. Flow cytometric cell cycle analysis performed on HT‐1080 cells revealed that the most cytotoxic compounds 48, 50, 54, 59, and 63 inhibit the S‐phase and arrest the cells in the G2/M phase of the cell cycle suggesting an antimitotic action of these compounds.