The invention provides compounds of formula I: (I) wherein A, B, W, Y, Z, R
1
, R
3
and R
4
have any of the meanings defined in the specification and their salts as well as additional compounds and their salts. The invention also provides pharmaceutical compositions comprising a compound of the invention, processes for preparing compounds of the invention, intermediates useful for preparing compounds of the invention, and therapeutic methods for treating cancer, a bacterial infection or a fungal infection using compounds of the invention.