Synthesis of 5,6-dihydropyrrolo[2,1-a]isoquinolines featuring an intramolecular radical-oxidative cyclization of polysubstituted pyrroles, and evaluation of their cytotoxic activity

A three-step protocol for the synthesis of 1,2,3,8,9-pentasubstituted-5,6-dihydropyrrolo[2,1-a]isoquinolines is described, using van Leusen's polysubstituted pyrrole construction followed by intramolecular radical-oxidative cyclization of the isoquinoline system. The cytotoxic activities of the dihydropyrroloisoquinolines were tested on six tumor cell lines. Preliminary structure-activity studies revealed the importance of the identity of the aromatic substituent at the C-2 position, particularly a phenyl, m-(amino) phenyl or m-(cyclohexylmethylpiperazinamide) phenyl substituent, for cytotoxic activity.