Annonacin (1) was isolated from the North American pawpaw ( Asimina triloba), as reported earlier from these laboratories. Natural 1 was submitted to the rat aortic ring bioassay for evaluation of antiangiogenic activity and was found to inhibit microvessel growth (IC50 value of 3 μM). 4,10,15,20-Tetraazido derivatives of 1 were prepared by permesylation followed by azide displacement or by iodination followed by azide displacement. The tetraazide derived from mesylation/azidation was antiangiogenic, while that derived from iodination/azidation exhibited no appreciable activity. The membrane permeability of natural 1 was evaluated using the parallel artificial membrane permeability assay and was found to be marginally permeable as compared to several clinically relevant compounds.