Anti-cancer activities of pyrazolo[1,5-a]indole derivatives.

The structure activity relationship (SAR) in the anti-cancer activities of pyrazolo[1,5-a]indole derivatives was investigated, and the following conclusions were obtained: 1) N(1)-quaternarization is essential for anti-cancer activity, 2) the size and polarity of the 2-substituent is crucial for in vitro activity which allows further investigation in an in vivo test, 3) the effect of the 4-substituent on the activity is minor compared with the other two factors.