Occurrence of hopanoid lipids in anaerobic Geobacter species

Geobacter metallireducens and G. sulfurreducens have been classified as strictly anaerobic bacteria which grow and thrive in subsurface and sediment environments. Hopanoids are pentacyclic triterpenoid lipids and are important for bacterial membrane stability and functioning. Hopanoids predominantly occur in aerobically growing bacteria of oxic environments. They rarely have been found in facultatively anaerobic bacteria and, to date, not at all in strict anaerobes. Our research shows that anaerobically grown G. metallireducens and G. sulfurreducens bacteria contain a range of hopanoid lipids, such as diploptene (i.e. hop-22(29)-ene) and hop-21-ene, and more complex, elongated hopanoids. In geological formations, diagenetic derivatives of hopanoids are widely used as biomarkers and are recognized as molecular fossils of bacterial origin. To date, these biomarkers have largely been interpreted as those derived from ancient oxic environments. Our findings presented here suggest that this interpretation needs to be re-evaluated. In addition to the origin in oxic environments, 'geohopanoids' may originate from ancient anaerobic environments as well.     

Triterpenoids from Gentiana scabra

Five triterpenoids, (20S)-dammara-13(17),24-dien-3-one, (20R)-dammara-13(17),24-dien-3-one, chirat-16-en-3-one, chirat-17(22)-en-3-one and 17beta,21beta-epoxyhopan-3-one, were isolated from the rhizomes and roots of Gentiana scabra together with five known ones, chiratenol, hop-17(21)-en-3-one, hop-17(21)-en-3beta-ol, lupeol and alpha-amyrin. The structures of new compounds were elucidated on the basis of spectroscopic studies.     

Synthesis of fluorinated 3β-hydroxypregn-5-en-20-one derivatives

Treatment of the unstable 3β-hydroxy-20, 20-dimethoxypregn-5-ene 3-acetate with acetic anhydride at reflux temperature gave a mixture of 3β-hydroxy-20-methoxypregna-5, 17(20)-diene and 3β-hydroxy-20-methoxypregna-5, 20-diene 3-acetates. Fluorination of this mixture with perchloryl fluoride afforded after fractionated crystallization 3β-hydroxy-17-fluoro-20-methoxypregna-5, 20-diene 3-acetate. Acid hydrolysis of the reaction mixture and subsequent Chromatographic separation led to 3β-hydroxy-17-fluoropregn-5-en-20-one 3-acetate and 3β-hydroxy-21-fluoropregn-5-en-20-one 3-acetate. 3β-Hydroxy-17-fluoro-20-methoxypregna-5, 20-diene 3-acetate did not react further with perchloryl fluoride even under forcing conditions. Fluorination of 3β-hydroxy-20-(N-ethyl benzylamino)-pregna-5, 17(20)-diene gave 3β-hydroxy-17, 21-difluoro-pregn-5-en-20-one, exclusively.     

Towards the characterization of squalene synthase activity in extracts of Zymomonas mobilis

Abstract Extracts of Zymomonas mobilis in the presence of NADPH converted tritium-labelled farnesyl diphosphate (FPP) into squalene, resulting from the activity of squalene synthase, as well as diploptene and diplopterol, derived from further squalene cyclisation. An unidentified isoprenoid representing up to 70% of the conversion products of FPP and different from presqualene alcohol was also formed, even in the absence of NADPH. Addition of squalestatin 1, an inhibitor of squalene synthase, blocked biosynthesis from FPP of the three former triterpenes, in accordance with the role of squalene synthase in their formation, as well as that of the unknown compound.     

Biosynthesis of rice phytoalexins: identification of putative diterpene hydrocarbon precursors.

A procedure for the preparation of a cell-free enzyme solution from rice leaves capable of catalyzing the biosynthesis of diterpene hydrocarbons from geranylgeranyl pyrophosphate or copalyl pyrophosphate as added substrates has been developed. The rates of synthesis of a group of "pimaradiene-like" diterpene hydrocarbons are about 75-fold higher with geranylgeranyl pyrophosphate as substrate and about 8-fold higher with copalyl pyrophosphate as substrate in comparison with extracts from untreated control leaves. The maximum rate of diterpene hydrocarbon biosynthesis is seen in extracts prepared at 40 h after uv irradiation. Five diterpene hydrocarbons (compounds A-E) were present in the hydrocarbon fraction biosynthesized from [3H]geranylgeranyl pyrophosphate in large-scale incubation mixtures prepared from uv-treated rice leaves. Three of these diterpenes were identified as ent-kaur-16-ene (B), ent-sandaracopimara-8(14), 15-diene (D), and 9 beta H-pimara-7,15-diene (E) from GC retention times and GC-MS spectral characteristics in comparison with those of authentic reference compounds. Compound C has spectral characteristics analogous to those of a pimaradiene, but a specific structural assignment from the data available was not possible. Similar incubations with [3H]copalyl pyrophosphate as the substrate and enzyme prepared from uv-treated rice leaves produced ent-kaurene (B), ent-sandaracopimara-8(14),15-diene (D), and compound C, but not 9 beta H-pimara-7,15-diene (E). These results are consistent with a proposed biosynthetic scheme in which 9 beta H-pimara-7,15-diene serves as a precursor of the momilactone family, and ent-sandaracopimara-8(14),15-diene serves as a precursor of the oryzalexin family of rice phytoalexins. ent-Kaurene was the only diterpene detected in incubation mixtures containing enzyme extract from untreated rice leaves and [3H]copalyl pyrophosphate as the substrate. It is suggested that kaurene biosynthesis in rice leaves is probably associated with gibberellin biosynthesis and the regulation of vegetative growth rather than stress metabolism. The diterpene cyclization enzymes in extracts of uv-treated rice leaves show only a relatively modest inhibition by the plant growth retardants AMO-1618 and Phosfon D. No evidence was obtained for the subcellular localization of these cyclization enzymes in organellar preparations; it is tentatively concluded that the enzymes are present predominantly in the extraorganellar cytoplasm of rice leaves.     

Dammaradiene synthase, a squalene cyclase, from Dryopteris crassirhizoma Nakai

Ferns produce a variety of cyclic triterpene hydrocarbons in large amount. Squalene cyclases (SCs) are responsible enzymes for formation of cyclic triterpene hydrocarbon skeletons. Although more than ten bacterial SCs have been cloned and four of them characterized for their enzymatic products, the only example of a fern SC is ACH, from Adiantum capillus-veneris, which produces hydroxyhopane. To obtain a deeper understanding of the molecular evolution of SCs and the origin of the structural diversity of fern triterpenes, further cloning and characterization of SCs have been pursued. In this study, a SC cDNA, DCD, was cloned from Dryopteris crassirhizoma by homology-based RT-PCR. DCD contains a 2058-bp open reading frame that encodes a 685 amino acid polypeptide exhibiting 66% identity to the previously identified fern SC, ACH, and 35-40% identity to bacterial SCs. Heterologous expression of DCD in yeast established it to be a dammaradiene synthase affording dammara-18(28),21-diene, a tetracyclic triterpene hydrocarbon. Although neither this compound nor any derived metabolites have been previously reported from D. crassirhizoma, re-investigation of the leaflets demonstrated the presence of dammara-18(28),21-diene. DCD represents the first SC that produces a tetracyclic triterpene hydrocarbon.     

Volatile components from European liverworts Marsupella emarginata,M. aquatica and M. alpina

The hydrodistillation products of the liverworts Marsupella emarginata, M. aquatica and M. alpina were investigated by spectroscopic methods. A number of new compounds could be isolated by preparative gas chromatography (GC) and identified by spectroscopic techniques including GC-mass spectrometry, NMR and chemical correlations in conjunction with enantioselective GC. From M. emarginata, in addition to many known compounds, the sesquiterpene hydrocarbon (-)-7-epi-eremophila-1(10),8,11-triene (1) and the sesquiterpene derivatives (-)-4-epi-marsupellol (2), (-)-marsupellol acetate (18), (-)-4-epi-marsupellol acetate (4), (+)-5-hydroxymarsupellol acetate (5) and (-)-9-acetoxygymnomitr-8(12)-ene (24) could be identified. In M. aquatica the sesquiterpene hydrocarbons (-)-myltayl-8(12)-ene (7), ent-(+)-amorpha-4,11-diene (8), (-)-amorpha-4,7(11)-diene (9), the sesquiterpene alcohol (+)-9-hydroxyselina-4,11-diene (10) and (-)-2-acetoxyamorpha-4,7(11)-diene (11) were identified. In M. alpina (-)-trans-selina-4(15),11-dien-5-ol (12), (+)-8,9-epoxyselina-4,11-diene (13) and (+)-cis-selina-4(15),11-dien-5-ol (14) were found as new natural products.     

Sesqui- and diterpenes from the liverwort Gackstroemia decipiens

Six rosanes, 5 beta,11 beta-dihydroxy-ros-15-ene, 5 beta,12 beta-dihydroxy-ros-15-ene, 11 beta-hydroxy-7-oxo-rosa-5,15-diene, 1 alpha,5 beta,11 beta-trihydroxy-7-oxo-ros-15-ene, 5 beta,20-epoxy-20-hydroxy-ros-15-ene and 5 beta,20-epoxy-20-methoxy-ros-15-ene along with the enantiomer of the already reported 11 beta-hydroxy-rosa-5,15-diene and the known 5 beta-hydroxy-ros-15-ene have been isolated from the liverwort Gackstroemia decipiens. Furthermore, the sesquiterpenes 3-acetoxy-7,11-dihydroxy-farnesa-1,5,9-triene and 1 beta,10 beta-epoxy-nardosin-7,11-diene were identified. Their structures were elucidated by NMR spectroscopy.     

21beta-Hydroxy-oleanane-type triterpenes from Hippocratea excelsa

Stem bark of Hippocratea excelsa afforded six pentacyclic triterpenes, five oleanane and one ursane types. They were identified as 11beta,21beta-dihydroxy-olean-12-ene-3-one (2), 3alpha,11alpha,21beta-trihydroxy-olean-12-ene (3), 3alpha,21beta-dihydroxy-11alpha-methoxy-olean-12-ene (4), 3alpha,21beta-dihydroxy-olean-9(11),12-diene (5), 3alpha,21beta-dihydroxy-olean-12-ene (6) and 3alpha,21beta-dihydroxy-11alpha-methoxy-urs-12-ene, isolated as its diacetate derivative (7), as well as 3alpha,21beta-dihydroxy-olean-12-ene (1) previously isolated from the root bark. The known alpha- and beta-amyrin, oleanoic and ursolic acids, trans-polyisoprene, and the ubiquitous beta-sitosterol were also isolated. Structures were elucidated on the basis of spectroscopic analyses, including homo- and heteronuclear correlation NMR experiments (COSY, ROESY, HSQC and HMBC) and comparison with literature data. The antigiardial activity of compounds 2-5 was not significant.     

Studies on Triterpenoid Constituents Isolated from the Roots of Sabia schumanniana

Five triterpenoids were isolated from the roots of Sabia schurnanniana Diels. Based on their physical constants, UV. IR, 1H-NMR, 13C-NMR, DEPT spectroscopic analysis and preparation of their derivatives, they were identified as 3-oxo-olean-ll, 13 (18)-diene (1), 3, 1 1-dioxo-olean- 12-ene (2), 3β -hydroxy-olean- 11, 13 (1 8) -diene (3), 3-oxo, 11 α-hydroxy-olean-12-ene (4), 3, 11α-dihydroxy-olean-12-ene (5) . Compound 4 is a new compound. Their 13C-NMR spectra have been signified by means of DEPT analysis.     

Profiles of the utilization of 20 amino acids as the only source of nitrogen and carbon in bacteria of the genera Klebsiella, Enterobacter, Serratia, Escherichia

The profiles of the utilization of 20 protein amino acids in 118 Klebsiella pneumoniae sub- sp. pneumoniae, K. oxytoca, K. planticola, K. mobilis, Enterobacter cloacae, Serratia marscescens, S. liquefaciens, Escherichia coli strains isolated from clinical material were studied. The utilization of amino acids was determined on minimal saline agar containing amino acid as the only source of nitrogen and carbon; the results were evaluated after 72-hour incubation at 37 degrees C. 17 profiles of amino-acid utilization were thus determined, most of them genus-specific in enterobacteria: Klebsiella (profiles No. 1--6, 9, 10), Enterobacter (No. 11--13), Serratia (No. 14--16), Escherichia (No. 17). The full coincidence of amino-acid utilization profiles in bacteria of K. mobilis (No. 1, 6) and K. pneumoniae subsp. pneumoniae with out of such profiles in bacteria of the genera Enterobacter, Serratia, Escherichia was established, which confirmed that K. mobilis (formerly Enterobacter aerogenes) belonged to the genus Klebsiella.     

Constituents of various wood-rotting basidiomycetes

Phytochemical investigation of n-hexane and methanol extracts of fruiting bodies of the wood-rotting fungi Fomitopsis pinicola. Ganoderma lipsiense, Fomes fomentarius and Gloeophyllum odoratum led to the isolation and identification of several triterpene derivatives and some aromatic compounds derived from lignin. These are the new natural products, namely, pinicolic acid E (16alpha-hydroxy-3-oxolanosta-8,24-dien-21-oic acid) and pinicolol C (3-oxolanosta-7,9(11),24-trien-15alpha,21-diol) from the crust of F. pinicola, ganoderenic acid D [(E)-7beta-hydroxy-3,11,15,23-tetraoxolanosta-8,20(22)-di en-26-oic acid] and ganoderic acid N (7beta,20-dihydroxy-3,11,15,23-tetraoxolanost-8-en-26-oic acid) from G. lipsiense and ergosterol peroxide (5alpha,8alpha-epi-dioxyergost-6-en-3beta-ol) as well as ergost-7-en-3-one from F. fomentarius. From G. odoratum, dehydroeburicoic acid [24-methylene-3-oxolanosta-7,9(11)-dien-21-oic acid], the dimethylacetal of 4,4,14alpha-trimethyl-24-oxo-5alpha-chol-8-en-21-oic acid and some aromatic compounds, of which 1-(4'-methoxyphenyl)-1,2-ethandiol is a new natural product, were isolated. Furthermore, a complete set of 13C NMR data of the steryl esters 3beta-linoleyloxyergosta-7,24(28)-diene, 3beta-linoleyloxyergosta-7,24-diene and 3beta-linoleyloxyergost-7-ene, which could be identified as a mixture in all investigated fungi, could be recorded. It was proved by HPLC and TLC investigations, that the crust on top of the fruiting bodies of F. pinicola consists of lanostane derivatives.     

A paradox: elevated 21-hydroxypregnenolone production in newborns with 21-hydroxylase deficiency

21-Hydroxypregnenolone and its metabolite 5-pregnene-3 beta, 20 alpha 21-triol have been measured in the sulfate fraction of neonatal urine. These two steroids are the major two 21-hydroxylated 5-pregnenes produced by neonates and are almost exclusively excreted as disulfates. The excretions of these steroids by normal infants and infants with 21-hydroxylase deficiency were compared. In addition to measurement of the absolute excretion, the excretion relative to the total 3 beta-hydroxy-5-ene output was also determined. The results show that 21-hydroxypregnenolone excretion is highly elevated in 21-hydroxylase deficiency (affected, mean 887 micrograms/24 h, range 453-1431 micrograms/24 h; normal, mean 117 micrograms/24 h, range 17-263 micrograms/24 h), but when compared to excretion of other delta 5 steroids the excretion is slightly low [(21-hydroxypregnenolone + 5-pregnene-3 beta, 20 alpha, 21-triol)/total 3-beta-hydroxy-5-ene steroids, 2.9% affected; 3.6% normal]. This difference was not statistically significant. There is thus no evidence that the 21-hydroxylase acting on pregnenolone is deficient in congenital adrenal hyperplasia. The explanation of the normal activity of "pregnenolone 21-hydroxylase," although not clearly defined, is probably associated with two recent findings by other workers: (a) that the human fetus has an active 21-hydroxylase distinct from the adrenal enzyme and (b) that a 21-hydroxylase structurally very different from the adrenal enzyme, with high activity towards pregnenolone (but no activity towards 17-hydroxyprogesterone), has been isolated from rabbit hepatic microsomes.     

The synthesis of 13α-androsta-5,16-diene derivatives with carboxylic acid,ester and carboxamido functionalities at position-17 via palladium-catalyzed carbonylation

17-Alkoxycarbonyl- and 17-carboxamido-3β-hydroxy-13α-androsta-5,16-diene derivatives were synthetized in high yields in the palladium-catalyzed carbonylation reactions of the corresponding 3β-hydroxy-17-iodo-13α-androsta-5,16-diene. This substrate with a 17-iodo-16-ene functionality was obtained from the 17-keto derivative via its 17-hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethylguanidine). 17-Carboxamides were obtained by chemoselective aminocarbonylation through the use of amines, including amino acid esters, as N-nucleophiles. The 17-methoxycarbonyl-16-ene derivative was synthetized by using methanol as O-nucleophile. The parent compound of this series, the 17-carboxylic acid derivative, was formed in the presence of water via hydroxycarbonylation.     

Site-directed mutagenesis experiments on the putative deprotonation site of squalene-hopene cyclase from Alicyclobacillus acidocaldarius

To provide insight into the catalytic mechanism for the final deprotonation reaction of squalene-hopene cyclase (SHC) from Alicyclobacillus acidocaldarius, mutagenesis experiments were conducted for the following ten residues: Thr41, Glu45, Glu93, Arg127, Trp133, Gln262, Pro263, Tyr267, Phe434 and Phe437. An X-ray analysis of SHC has revealed that two types of water molecules ("front water" and "back waters") were involved around the deprotonation site. The results of these mutagenesis experiments allow us to propose the functions of these residues. The two residues of Gln262 and Pro263 probably work to keep away the isopropyl group of the hopanyl cation intermediate from the "front water molecule," that is, to place the "front water" in a favorable position, leading to the minimal production of by-products, i.e., hopanol and hop-21(22)-ene. The five residues of Thr41, Glu45, Glu93, Arg127 and Trp133, by which the hydrogen-bonded network incorporating the "back waters" is constructed, increase the polarization of the "front water" to facilitate proton elimination from the isopropyl moiety of the hopanyl cation, leading to the normal product, hop-22(29)-ene. The three aromatic residues of Tyr267, Phe434 and Phe437 are likely to play an important role in guiding squalene from the enzyme surface to the reaction cavity (substrate channeling) by the strong affinity of their aromatic residues to the squalene substrate.     

Synthesis of some epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives and evaluation of their biological activity

Steroidal epoxy and/or N-oxy 17-picolyl and 17-picolinylidene-androst-5-ene derivatives have been prepared using 3beta,17beta-dihydroxy-17alpha-picolyl-androst-5-ene (1), 3beta-acetoxy-17-picolinylidene-androst-5-ene (2), and 3beta-hydroxy-17-picolinylidene-androst-5-ene (3) as synthetic precursors. The compounds 2 and/or 3 were reacted with m-chloroperoxybenzoic acid (MCPBA). The compounds synthesized from 2 were 17-picolinylidene-N-oxide 4, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 5 and 6, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 7 and 8. Starting from compound 3, a mixture of 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene 9 and 10, 5alpha,6alpha-epoxy and 5beta,6beta-epoxy-17-picolinylidene-N-oxide 11 and 12, and 5alpha,6alpha:17alpha,20alpha- and 5beta,6beta:17alpha,20alpha-diepoxy-N-oxide 13 and 14 were obtained. From compounds 15 and 18, obtained from 1 and 3 by the Oppenauer oxidation, the 4alpha,5alpha-epoxy and 4beta,5beta-epoxy derivatives 16, 17 and 20, 21 were prepared by oxidation with 30% H(2)O(2). Oxidation of 18 with MCPBA yielded only the N-oxide 19. The structures of compounds 15 and 18 were proved by the X-ray analysis. Compounds 1-6, 9, 15, 17, 18, and 21 were tested on activity against the enzyme aromatase. Antitumor activity against three tumor cell lines (human breast adenocarcinoma ER+, MCF-7, human breast adenocarcinoma ER-, MDA-MB-231, and prostate cancer PC3) was evaluated. Three tested compounds (1, 4, and 19) showed strong activity against PC3, the IC(50) values being in the range 0.55-10microM, whereas compound 17 showed strong activity against MDA-MB-231 (IC(50) 10.4microM).     

Purification, partial characterization and substrate specificity of a squalene cyclase from Bacillus acidocaldarius

From the thermophilic Bacillus acidocaldarius, a membrane bound cyclase catalysing the formation of 22(29)-hopene (diploptene) and 22-hopanol (diplopterol) from squalene was enriched 670-fold to a purity of 95% as judged by gel chromatography. The specific activity of the purified enzyme in the presence of Triton X-100 is 0.22 mumol product formation per min and mg protein at 54 degrees C. The molecular mass is 150 kDa and that of the subunits 80 kDa as determined by FPLC gel chromatography and sodium dodecyl sulfate gel electrophoresis, respectively. Not only squalene but also E,E-homofarnesol, homogeraniol and homofarnesyl (1,5,9-trimethyl-4,8-decadienyl) ether are substrates. The ether bond of the latter substrate is split by the enzyme. The products of the aforementioned three additional substrates are ambroxan (dodecahydro-3a,6,6,9a-tetramethylnaphtho[2,1-b]-furan), octahydro-4,4,7a-trimethylbenzofuran and ambroxan together with 1,5,9-trimethyl-4,8-decadienol. The cyclization rates of these substrates compared to squalene are 3%, 0.05% and 0.3%, respectively. The half-life of the enzyme activity is 80 h at 45 degrees C and 18 h at 54 degrees C.     

Diterpene biosynthesis in maize seedlings in response to fungal infection

A cell-free system which catalyzes the biosynthesis of terpene hydrocarbons when supplemented with mevalonate, Mn²⁺, and ATP was prepared from the scutellum-embryonic axis region of maize seedlings. The capacity of this system for the production of terpene hydrocarbons was enhanced 50- to 100-fold when the seedlings were exposed for 48 hours to the fungus Rhizopus stolonifer prior to tissue homogenization. The fungi Aspergillus niger, Fusarium moniliforme, and Verticillium albo-atrum also elicited this biosynthetic enhancement. The terpene hydrocarbon products were separable into six fractions by argentation thin layer chromatography. Radioactivity was contributed to five of these fractions when either geranylgeranyl pyrophosphate or copalyl pyrophosphate was supplied as substrate, suggesting that polycyclic diterpenoid hydrocarbons were the main products. Large scale biosynthetic reactions led to the acquisition of about 1 milligram of terpene hydrocarbon products plus some more polar terpenoid products. Analysis of the hydrocarbon products by gas chromatography and mass spectrometry led to the separation of six distinct diterpene hydrocarbons plus a fraction with a molecular weight of about 550. Three of the diterpene hydrocarbons were identified as kaur-16-ene, kaur-15-ene (isokaurene), and pimara-8(14),15-diene. None of the terpene hydrocarbon fractions tested displayed antifungal activity in the Cladosporium cucumerinum thin layer plate assay.     

Taxanes with C-5-amino-side chains from the needles of Taxus canadensis

Five taxanes with an amino-side chain on C-5 were identified for the first time in the needles of the Canadian yew, Taxus canadensis. Their structures were characterized as 2alpha,7beta,9alpha,10beta,13-pentaacetoxy-11beta-hydroxy-5alpha-(3'-N,N-dimethylamino-3'-phenyl)-propionyloxytaxa-4(20),12-diene (1), 2alpha,9alpha-dihydroxy-10beta,13alpha-diacetoxy-5alpha-(3'-methylamino-3'-phenyl)-propionyloxytaxa-4(20),11-diene (2), 2alpha17-dihydroxy-9alpha,10beta,13alpha-triacetoxy-5alpha-(3'-N,N-dimethylamino-3'-phenyl)-propionyloxytaxa-4(20),11-diene (3), 2alpha-hydroxy-7beta,9alpha,10beta,13alpha-tetraacetoxy-5alpha-(2'-hydroxy-3'-N,N-dimethylamino-3'-phenyl)-propionyloxytaxa-4(20),11-diene (4), and 9alpha-hydroxy-2alpha,10beta,13alpha-triacetoxy-5alpha-(3'-N,N-dimethylamino-3'-phenyl)-propionyloxytaxa-4(20),11-diene (5) on the basis of 1D-, 2D-NMR spectroscopic data and high-resolution fast atom bombardment MS analyses. Metabolite (1) was isolated from the needles of the Canadian yew for the first time but had previously been detected in the stems of the Japanese yew, whereas taxanes (2-5) are only now reported. Metabolite (3) is the first reported nitrogen-containing taxane with a 17-hydroxyl substitution.