New allo-cedrane type sesquiterpene hemiketals and further sesquiterpene lactones from fruits of Illicium floridanum

Three new tetracyclic sesquiterpene hemiketals possessing the very rare all o-cedrane carbon skeleton, debenzoyl-7-deoxo- 1 alpha, 7 alpha -dihydroxyta shironin, debenzoyl-7-deoxo-7 alpha -hydroxytashironin, and debenzoyl- 7-de oxo-7 alpha -hydroxy-3-oxotashironin (1-3), were isolated from the fruits o f Illicium floridanum ELLIS (American Star Anise, Star bush). Their structu res were elucidated by mass and NMR spectroscopic analyses. The molecular s tructure of 1, including absolute stereochemistry, was determined by single -crystal X-ray diffraction of its monohydrate. Only one compound of this ty pe, tashironin, has previously been isolated from Illicium tashiroi. Furthe rmore, a new sesquiterpene lactone of the seco-prezizaane type, 3,4-anhydro -13,14-dihydroxyfloridanolide (4), and the known anislactone B (5) were iso lated. The occurrence of further allo-cedrane sesquiterpenes in another Ill icium species confirms the hypothesis of previous authors that this type of compound is a biogenetic precursor of the typical seco-prezizaane sesquite rpene lactones found in this genus. Moreover, regarding their co-occurrence with anislactone B as reported here, they may also be considered precursor s for the anislactone skeletal type.