| Research Abstract |
1. Three kinds of yew trees, Japanese yew Taxus cuspidata (needles and seeds) and Chinese yews T. mairei (sees, bark, and needles) and T. yunnanensis (seeds), were investigated, and about 200 compounds including taxoids, flavonoids, ligananes, ecdysteroids, abietanes, 9(10→20)-abeo abietanes, vomifoliol and its derivatives were isolated.
2. More than 70 new taxoids including almost all the structural types were isolated form above three kinds of yew trees, and their structures were established through spectroscopic methods including 1D and 2D NMR techniques.
3. 2(3→20)-Abeotaxanes and bicyclic taxoids were rare in the nature. Among more than 300 taxoids only eight 2(3→20)-abeotaxanes and six bicyclic taxoids were reported in the past researching. In this work, besides six known bicyclic taxoids and six out of eight known 2(3→20)-abeotaxanes, nineteen new bicyclic taxoids and ten new 2(3→20)-abeotaxanes were added to these two smaller groups.
4. Several crucial intermediates were isolated from yew trees for the first time, especially taxoid with 4(5),11-diene and bicyclic taxoid with a 7-en-9-one structural unit (a verticillene skeleton) has never been isolated from Taxus species in the past studies. Accordingly, the isolation of these two kinds of compounds from yew trees may shed light on the biosynthesis of taxane diterpenoids, and also afford new clues for the total synthesis of paclitaxel and related compounds.
5. It was found that T. cuspidata distributed in Shikoku area contained a relatively high level of taxol in the leaves, and that a bicyclic taxane diterpenoids showed the anticancer activity.
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