Taxoids from the Roots of Taxus × media cv. Hicksii (original) (raw)
1994, Journal of Natural Products
A%mm.-The roots of TaxusXmpdia cy. Hicksii gave two new pseudoalkaloidal taxoids, identified as N-debenzoyl-N-butanoyl taxol [l] and 7/3-acetoxy-9-acetylspicataxine [2a]. A new baccatin IV derivative Val and the lignans hydroxymatairesinol [SI and (-)-epinomachelogenin E91 were also isolated. The epoxidation of Aqz0)''' taxadienes was investigated, disclosing an unusual reactivity of the bridgehead double-bond towards peracids. Regiochemically and stereochemically unnatural epoxides of taxoids were obtained. Nmr data for these compounds were compared with literature values on the natural epoxides. No significant correlation between the configuration of the 4(20)-oxirane ring and the chemical shift of H-5 was found. The stem bark and the needles of several species of yew have been thoroughly investigated (2), but very few studies have been done on the constituents of the roots (3,4). As part of a study aimed at assessing the availability of taxol and taxol-equivalent diterpenoids from cultivated yew species, we investigated the constituents of the roots of T. Xmediu Rehd. cv. Hicksii (5). This yew was developed for ornamental purposes and is popular as landscape material. Extensive cultivations exist in nurseries, and the needles have been studied as a potential source of taxol(6). A previous study has shown the presence of taxol and two novel analogs in the roots (7). We report here the isolation of three new taxoids El, 2a, 7a7 and of a lignan not previously described as a natural product E97. RESULTS AND DISCUSSION ' Compound 1 has the molecular formula C44H53N0,4 (cims). Its 'H-nmr spectrum was similar to that of taxol C (N-debenzoyl-N-hexanoyl taxol) (7). The only significant difference was the absence of the w-2 and w-3 methylene protons of the N-acyl residue. The 13C-nmr spectrum was almost superimposable on that of taxol C (7) except for the absence of the 0-2 and 0-3 carbons. These data suggested that 1 differs from taxol C by 'Part 14 in the series "The Chemistry and Occurrence of Taxane Derivatives." For part 13, see Appendino et al. (1).
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