Synthesis and antitumor activity of duocarmycin derivatives: A-ring pyrrole compounds bearing cinnamoyl groups.

A series of N-cinnamates of the A-ring pyrrole compound of duocarmycin were synthesized and evaluated for in vitro anticellular activity against HeLa S3 cells and in vivo antitumor activity against murine sarcoma 180 in mice. The 4'-methoxy- and 4'-BocNH-cinnamates exhibited strong in vitro anticellular activity among the synthesized compounds. The ortho substitution of the 4'-methoxycinnamate did not affect the anticellular activity and contributed to an enhancement of water solubility. Most of the 8-O-(N,N-dialkylcarbamoyl) derivatives of the 4'-methoxycinnamate displayed remarkably superior in vivo antitumor activity to duocarmycin A or B2. Moreover, it is noteworthy that these 8-O-(N,N-dialkylcarbamoyl) derivatives exhibited significant antitumor activity at wider range of doses as compared with the A-ring pyrrole derivatives having the trimethoxyindole skeleton in segment B.