NEW MYRSINOL-RELATED POLYFUNCTIONAL PENTACYCLIC DITERPENE ESTERS FROMROOTS OF EUPHORBIA-PROLIFERA

Five Eupborbia substances, SPr1-SPr5, were isolated from the roots of Euphorbia prolifera. They were found to have similar structures bur we re inactive in a mouse ear inflammation assay. By nmr analysis and aft er single-crystal X-ray crystallography the structure of SPr5 was esta blished as a hexaester (tetraacetate-benzoate-propionate) of a hithert o unknown polyfunctional pentacyclic diterpene parent alcohol, structu rally related to myrsinol. As judged from its nmr spectra, SPr4 is an analogue of SPr5, carrying an isobutyrate substituent in place of a be nzoate ester functionality. SPr1-SPr3 were partially characterized by their mass spectra as esters of diterpene parent alcohols possibly rel ated to the myrsinol structure. SPr1-SPr5 may represent one of the pro duct lines branching off the proposed main route of biogenesis of the oligocyclic diterpenoid skin irritants and tumor promoters occurring i n many, but not all, of the species in the plant families Thymelaeacea e and Euphorbiaceae.