Two new antineoplastic diterpenes from Taxus mairei

A New abeo-Icetexane-Type Diterpenoid from the Stem Barks of Taxus wallichiana

From a CH2 Cl2 -soluble fraction of the stem barks of Taxus wallichiana, one new abeo-icetexane-type diterpenoid, taxamairin I (1), was isolated. Its absolute configuration was elucidated based on spectroscopic interpretation and time-dependent density functional theory (TD-DFT) calculation of optical rotation. In addition, the plausible biosynthesis pathway for the formation of the new abeo-icetexane-type diterpenoid was proposed. Taxamairin I (1), at a concentration of 100 μM, did not show cytotoxicity against Hep3B human liver cancer cell lines.

Recent Developments with Icetexane Natural Products

Icetexane diterpenoids are a diverse family of natural products sourced from several species of terrestrial plants. Icetexanes exhibit a broad array of biological activities and together with their complex 6-7-6 tricyclic scaffolds, they have piqued the interest of synthetic organic chemists, natural products chemists, and biological investigators over the past four decades and were reviewed 13 years ago. This review summarizes icetexane natural products isolated since 2009, provides an overview of new synthetic approaches to the icetexane problem, and proposes an additional classification of icetexanes based on novel structures that are unlike previously isolated materials.

Gold-Catalyzed Synthesis of Icetexane Cores: Short Synthesis of Taxamairin B and Rosmaridiphenol

We report the short synthesis of two natural products, rosmaridiphenol and taxamairin B, from key intermediates 5a and 5b, which were prepared from enynals 8a and 9b, respectively, by using a gold-catalyzed cyclization reaction. This approach can be widely applied in the synthesis of [6,7,6]-fused tricyclic compounds found in many icetexane diterpenoids.

Synthesis of Naturally Occurring Tropones and Tropolones

Tropones and tropolones are an important class of seven-membered non-benzenoid aromatic compounds. They can be prepared directly by oxidation of seven-membered rings. They can also be derived from cyclization or cycloaddition of appropriate precursors followed by elimination or rearrangement. This review discusses the types of naturally occurring tropones and tropolones and outlines important methods developed for the synthesis of tropone and tropolone natural products.

A New Metabolite with a New Substitution Pattern from the Seeds of the Chinese Yew,Taxus mairei

A new taxoid metabolite with a new substitution pattern was isolated from the methanol extract of the seeds of Taxus mairei, and its structure was established as 5alpha,15-dihydroxy-7beta,9alpha-diacetoxy-11(15-->1)abeo-taxa-4(20),11-dien-13-one (1) on the basis of spectral analysis including (1)H- and (13)C-NMR, HMQC, HMBC, NOESY, and confirmed by HR-FAB mass spectrometry.

New taxanes from the seeds of Taxus mairei

Two new taxoid metabolites were isolated from the methanol extract of the Taxus mairei seeds. Their structures were established as 2alpha-hydroxy-9alpha,10beta,13alpha-triacetoxy-5alpha-cinnamoyloxytaxa-11-en-4beta,20-epoxide (1) and 2'-acetyl taxol (2) on the basis of spectral analysis.

Three novel bicyclic 3,8-secotaxane diterpenoids from the needles of the chinese yew, taxus chinensis var. mairei

Three novel (1-3) and five known bicyclic 3,8-secotaxane diterpenoids were isolated from the needles of the Chinese yew, Taxus chinensis var. mairei. The structures of the new compounds were established, respectively, as (3E,7E)-2alpha,10beta, 13alpha-triacetoxy-5alpha,20-dihydroxy-3,8-secotaxa-3,7, 11-trien-9-one (1), (3E,7E)-2alpha,10beta-diacetoxy-5alpha,13alpha, 20-trihydroxy-3,8-secotaxa-3,7,11-trien-9-one (2), and (3E,8E)-7beta, 9,10beta,13alpha,20-pentaacetoxy-3,8-secotaxa-3,8,11-triene-2alpha, 5alpha-diol (2-deacetyltaxachitriene A) (3), on the basis of spectral analysis. The other five bicyclic taxane diterpenoids were determined as canadensene, 5-deacetyltaxachitriene B, taxachitriene B, taxuspine U, and taxuspine X by comparison of their physical properties and spectral data with those previously reported.