1. For a recent review seeM. N. Galbraith, D. H. S. Horn, S. Itô, M. Kodama andJ. M. Sasse, Agric. Biol. Chem36 2393 (1972).
2. Tumor-inhibitory activity and cytotoxicity were assayed under the auspices of the National Cancer Institute, by the procedures described byR. I. Geran, N. H. Greenberg, M. M. McDonald, A. M. Schumacher andB. J. Abbott (Cancer Chemother. Rep. part 3,3, 1 (1972)). Podolide showed significant activity in vivo against P-388 leukemia in mice and cytotoxicity in vitro towards cells derived from both human carcinoma of the nasopharynx (KB) and P-388 murine leukemia.
3. Podolide was accompanied by trace amounts of its 2,3-dihydro derivative which could be removed by fractional crystallization from methanol.
4. S. Itô, M. Kodama, M. Sunagawa, T. Takahashi, H. Imamura andO. Honda, Tetrahedron Lett.1968, 2065.
5. The diol (2) was characterized as its diacetate (3), C23H30O7, mp 144–145°.