Phorbol Derivatives of Croton Oil

One new seco-cyclic phorbol derivative and one new phorbol 12-monoester, named 13-oxo-14-isopropylphorbol (2), 12-angelylphorbol (5), together with four known compounds, named 4a-deoxyphorbol, 13-oxo-14-isopropenylphorbol, 12-isobutyrylphorbol, and phorbol-12-(2-methylbutyrate) were obtained by hydrolyzing croton oil. The structures of the compounds were elucidated by spectroscopic analysis. These compounds showed no cytotoxicity (CC50 > 200 μM). Phorbol-12-monoesters 4–6 showed the weak inhibitory activities on syncytia formation induced by HIV-1IIIB (4, EC50 = 56.05 μM; 5, EC50 = 72.97 μM; 6, EC50 = 52.58 μM). The seco-cyclic phorbol derivatives (2, 3) showed no anti-HIV-1 activities (EC50 > 200 μM), which indicated that chemical cleavage of cyclopropanols might affect anti-HIV-1 activity.