Potential antitumor agents. 60. Relationships between structure and in vivo colon 38 activity for 5-substituted...

9-Oxoxanthene-4-acetic acids are a class of antitumor agents effective against the mouse colon adenocarcinoma 38 in vivo. Within this class, 5-substituents on the xanthenone are known to enhance potency. To extend structure-activity relationships for the class, a series of derivatives bearing a wide variety of substituents at the 5-position have been prepared and evaluated. The results suggest that activity correlates better with the lipophilic properties of substituents rather than with their electronic properties. Generally, lipophilic substituents result in more active compounds, but there may be a size limitation on such substituents. The 5-methyl derivative is the most dose-potent of the analogues studied.