| abstract |
The invention provides compounds of formula I or formula II: n nwherein:n the bond represented by --- is a single bond or a double bond, and R 1 –R 5 , X, and Y have any of the meanings defined in the specification and their pharmaceutically acceptable salts. The invention also provides pharmaceutical compositions comprising a compound of formula I or II, processes for preparing compounds of formula I or II, intermediates useful for preparing compounds of formula I or II, and therapeutic methods for treating cancer and other topoisomerase related conditions using compounds of formula I or II. |