In order to study the structure-activity relationship of 7, 8-dimethoxy-2-methyl-3-(4, 5-methylenedioxy-2-vinylphenyl)isoquinoline-1(2H) -one (2), which has exhibited significant antitumor activity, chemical modifications of 2 were performed to yield the corresponding products (3-7). Further systematic uses of an efficient procedure for the synthesis of 3-arylisoquinoline derivatives produced the substituted compounds (9a-9g), which were tested for in vitro antitumor activity against five different human cancer cell lines.