Crotofolane-Type Diterpenoids: Crotocascarins R–V, Rearranged Trinorcrotofolane: Crotocascarin δ and a Phorbol Derivative from the Leaves of Croton cascarilloides

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Five new crotofolanes, named crotocascarins R–V (1–5), one rearranged trinorcrotofolane, crotocascarin δ, and one phorbol derivative were isolated from the EtOAc-soluble fraction of the MeOH extract of the leaves of Croton cascarilloides. Crotocascarins R (1), T (3), and U (4) possessed isobutyric acid as an acyl moiety and crotocascarin B (2) an acetyl group, whereas crotocascarin V (5) was elucidated to be a hydroxylated compound of crotocascarin K at the 9-position. Crotocascarin δ (6) was a trinor rearranged crotofolane with a tertiary hemiketal functional group at the 8-position. The absolute configuration of the 8-position was determined by the comparison of the experimental electronic circular dichroism (ECD) spectrum and calculated ECD spectra. Compound 7 was a phorbol ester derivative with a peroxide functional group. The fatty acid attached at the 12-position was found to be a single species—i.e., lauric acid (C-12)—from the evidence of the mass spectral data.