The invention provides compounds of formula I or formula II:
wherein:
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.