Synthesis and antitumor activity of tropolone derivatives. 2.

Structural requirement for antitumor activity of tropolone derivatives 2-4 was explored. Isochroman derivatives (6-17, 20, and 23) and alpha, alpha-disubstituted compounds 26-30 were synthesized and their antitumor activities were tested. These nontroponoid derivatives were all inactive, implying that a tropolone ring is essential for the activity. Several compounds related to the monotropolone analogue 3 were synthesized. Among them, 31-33 showed significant activity, but their potencies were considerably weaker than those of binary tropolone analogues 4.