Reduced Benzimidazo[2,1- a ]isoquinolines. Synthesis and Cytotoxicity Studies

6-Butyl-5,6-dihydrobenzimidazo[2,1- a ]isoquinoline, 3,9- and 3,10-dimethoxy, and 3,9- and 3,10-dihydroxy analogues, and their 12-methyl quaternary salts were prepared by a multistep route. Cytotoxicities against 55 human cancer cell lines were measured in the National Cancer Institute screen. The quaternary salts of the dimethoxy compounds (15b/c) were clearly the most active overall, with a mean graph midpoint (MGM) value of 2 m.