The present invention relates to betulonic and betulinic acid derivatives and, in particular, to C-28 and C-3 derivatives. The present invention relates to betulonic acid esters, and dihydro-betulonic acid esters. Betulinic acid and derivatives thereof may be bound to a poly(alkylene glycol) (PAG) such as poly(ethylene glycol). Binding may be via a linker, such as a diamine, an amino acid, a peptide, an ester or a carbonate.The compounds of the present invention may be used for the treatment of cancer or a viral infection. The present invention also provides pharmaceutical compositions comprising the compounds of the present invention.
