abeo-taxane diterpenoids from the Taiwanese Yew Taxus sumatrana.

Chemical investigation of the acetonic extract of the leaves and twigs of Taxus sumatrana (Taxaceae) led to the isolation of four new taxane diterpene esters, taiwantaxins A-D (1-4, resp.). Their structures were determined primarily on the basis of 1D- and 2D-NMR techniques as well as MS. Compound 1 is a rearranged taxane diterpenoid possessing an opened oxetane ring moiety containing C(4), C(5), and C(20). The metabolites 2 and 3 belong to a 5/6/6 taxene system having a rare five-membered gamma-lactone ring comprising C(8), C(9), C(10), and C(19). Compound 4 is an example of a taxane diterpene containing a 6/8/6 ring system with a tetrahydrofuran ring comprising C(2), C(3), C(4), and C(20). The 11(15-->1)abeo-taxane diterpenoids, taiwantaxins A-C (1-3, resp.) are lacking an O-bearing functionality at either C(13) or C(14). Compound 2 showed significant cytotoxic activity against human PC-3 tumor cells.