New Taxanes from the Needles of Taxus canadensis

Ten new taxanes were isolated from the methanol extract of the needles of the Canadian yew, Taxus canadensis. On the basis of their spectral analysis, their structures were established as 9α-hydroxy-2α,7α,10β-triacetoxy-5α-cinnamoyloxy-3,11-cyclotaxa-4(20)-en-13-one (1), 9α,10β-diacetoxy-5α-cinnamoyloxy-3,11-cyclotaxa-4(20)-en-13-one (2), 9α,20-dihydroxy-2α,10β,13α-triacetoxytaxa-4(5),11(12)-diene (3), 2α,9α,10β-triacetoxy-20-cinnamoyloxy-11,12-epoxytaxa-4-en-13-one (4), 9α-hydroxy-2α,10β,13α-triacetoxy-5α-(3‘-methylamino-3‘-phenyl)-propionyloxytaxa-4(20),11-diene (5), 2α,10β-diacetoxy-5α,9α-dihydroxytaxa-4(20),11-dien-13-one (6), 2α,9α-diacetoxy-5α,10β-dihydroxytaxa-4(20),11-dien-13-one (7), 5α,9α-dihydroxy-2α,10β,13α-triacetoxytaxa-4(20),11-diene (8), 5α,10β-dihydroxy-2α,9α,13α-triacetoxytaxa-4(20),11-diene (9), and 7β,11β-dihydroxy-2α,9α,10β,13-tetraacetoxy-5α-cinnamoyloxytaxa-4(20),12-diene (10). Taxane 1 is the first example of a 3,11-cyclotaxane with a 7-epi-α-oxygenated group. Taxane 4 is the first taxane with a C-11,12-epoxide ring as well as a C-4(5)-endo-double bond. Taxanes with a 12(13) double bond as in 10 instead of the usual 11(12) double bond have been found so far only in the needles, stem, and seeds of the Japanese yew.