Tri‐ and Bicyclic Taxoids from the Taiwanese Yew Taxus sumatrana

Abstract Five new taxoids, including a new 2(3→20)‐abeo‐taxane with a 6/10/6‐membered ring system and four 3,8‐seco‐taxanes having a 6/12‐membered ring system, were isolated from an acetone extract of the leaves and twigs of the Taiwanese yew (Taxus sumatrana, Taxaceae). The structures were established as 2α,7β,10α‐triacetoxy‐5α‐hydroxy‐2(3→20)‐abeo‐taxa‐4(20),11‐dien‐9,13‐dione (1), (3E,8E)‐2α,9,10β, 13α,20‐pentaacetoxy‐7β‐hydroxy‐3,8‐secotaxa‐3,8,11‐trien‐5‐one (2), (3E,8E)‐2α,9,10β,13α,20‐pentaacetoxy‐5α,7β‐dihydroxy‐3,8‐secotaxa‐3,8,11‐triene (3), (3E,8E)‐9,10β,13α‐triacetoxy‐2α,7β,20‐trihydroxy‐5α‐[(2E)‐cinnamoyloxy]‐3,8‐secotaxa‐3,8,11‐triene (4), and (3E,8E)‐2α,5α,7β,9,10β,13α‐hexaacetoxy‐20‐hydroxy‐3,8‐secotaxa‐3,8,11‐triene (5), respectively, on the basis 1D‐ and 2D‐NMR spectral analyses. The in vitro cytotoxic activity of compounds 1–5 against four human tumor cell lines, including HeLa (cervical epitheloid), WiDr (colon), Daoy (medulloblastoma), and Hep2 (liver carcinoma) tumor cells was evaluated. Whereas compounds 1–3 were inactive, the novel taxanes 4 and 5 showed significant cytotoxicity.