New eremophilane-type sesquiterpenes from Ligularia lapathifolia.

Seven new eremophilanolides were isolated from the roots and rhizomes of Ligularia lapathifolia. Their structures were established as 3beta-angeloyloxy-8beta H-eremophil-7(11)-ene-12,8alpha (14beta, 6alpha)-diolide, 3beta-angeloyloxy-8beta-hydroxyeremophil-7(11)-ene-12,8alpha(14beta,6alpha)-diolide,3beta-angeloyloxy-8beta-methoxyeremophil- 7(11)-ene-12,8alpha(14beta,6alpha)-diolide,3beta-angeloyloxy-8beta-ethoxyeremophil-7(11)-ene-12, 8alpha (14beta,6alpha)-diolide, 3beta-angeloyloxy-10beta- hydroxyeremophil-8(9),7(11)-diene-12,8(14beta,6alpha)-diolide, 3beta-angeloyloxy-8,12-expoy-12alpha-hydroxy-8beta-methoxyeremophil-7(11)-en-14beta,6alpha-olide and 3beta-angeloyloxyeremophilan-7,11-dien-14beta,6alpha-olide, by means of spectroscopic analyses. Moreover, application of a photooxygenation reaction on 7 resulted in the generation of 2 with an alpha,beta-unsaturated gamma-lactone moiety. This biomimetic transformation supports a biogenetic pathway proposed for 2.