RESUMEN
The aerial parts of Euphorbia pithyusa subsp. cupanii collected in Sardinia afforded eleven novel diterpenoids belonging to the lathyrane (1a), premyrsinane (4a-g), and tigliane (5a-c) types. Compounds 4a-g and 5a are esters of two new parent alcohols, named premyrsinol and 4,12,20-trideoxyphorbol, respectively. Structures were elucidated by spectroscopic and chemical methods. Puzzling differences between the NMR data of lathyrol (1c) and its esters were rationalized in terms of flipping of the exomethylene around the mean plane of the macrocycle.
RESUMEN
A short and practical process for the isolation of ingenol (1a) from an agricultural commodity (the seeds of Euphorbia lathyris) is described. Macrocyclic diterpene esters are obtained as byproducts, and the esterification pattern of the Euphorbia factors L2 (3), L3 (4a), and L8 (4b) was established by 2D NMR measurements. Full spectroscopic data for these compounds are reported.