II. Synthesis and biological evaluation of some bioisosteres and congeners of the antitumor agent, 2-(4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy)propionic acid (XK469).

XK469 (1) is among the most highly and broadly active antitumor agents to have been evaluated in our laboratories. Subsequent developmental studies led to the entry of (R)-(+) 1 (NSC 698215) into phase 1 clinical trials (NIH UO1-CA62487). The antitumor mechanism of action of 1 remains to be elucidated, which has prompted a sustained effort to elaborate a pharmacophoric pattern of 1.