A large number of camptothecin (CPT) analogs have been prepared in the 20S, 20RS, and 20R configurations with a number of ring A substituents. Topoisomerase I (TI) inhibition data (ICw) have been obtained by standard procedures. In general, substitution at the 9 or 10 positions with amino, halogeno, or hydroxyl groups in compounds with 20s configuration results in compounds with enhanced TI inhibition. Compounds in the 20RS configuration ...