Isolation and Structural Characterization of New, Highly Functionalized Diterpenes from Euphorbia serrulata

Five new diterpene polyesters, 1–5, with jatrophane skeletons were isolated from the fresh whole plants of Euphorbia serrulata. The structure elucidation was performed by means of UV/VIS spectroscopy, HR‐ESI‐MS, and advanced two‐dimensional NMR methods, including 1H‐NMR, JMOD, 1H,1H‐COSY, NOESY, HMQC, and HMBC experiments. The relative configurations of 1–5 and their conformations in solution were analyzed on the basis of NOESY measurements. As a result of detailed NMR studies, complete 1H and 13C chemical‐shift assignments of the compounds were possible. The isolated compounds differ stereochemically and do not comprise a uniform series regarding the configurations at C(2), C(6), and C(13). Compound 5 possesses the new structural feature of a double bond with (Z)‐configuration in the macrocyclic ring of the jatrophane skeleton, while compound 2 has a CC bond in the five‐membered ring, this being the first observation of this structural feature in the type of macrocyclic Euphorbiaceae diterpenes.