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.