Two lathyrane diterpenoid stereoisomers containing an unusual trans-gem-dimethylcyclopropane from the seeds of Euphorbia lathyris

Abstract

Two novel lathyrane-type diterpenoids, the Euphorbia factors L_2a (1) and L_2b (2), and their stereoisomer Euphorbia factor L₂ (3) were obtained from seeds of Euphorbia lathyris. Both Euphorbia factors L_2a and L_2b possess an unprecedented trans-gem-dimethylcyclopropane as structural feature. Also, the Euphorbia factor L_2a is the first example of a lathyrane diterpenoid with an endocyclic 12(Z)-double bond. The structures of the molecules and their absolute configurations were elucidated by comprehensive spectroscopic analyses, Cu-Kα radiation X-ray diffraction, and comparison with calculated electronic circular dichroism (ECD) data. The Euphorbia factor L_2b exhibited an inhibitory effect against U937 cell line with an IC₅₀ value of 0.87 μM.