共查询到20条相似文献,搜索用时 15 毫秒
1.
Williams DC Carroll BJ Jin Q Rithner CD Lenger SR Floss HG Coates RM Williams RM Croteau R 《Chemistry & biology》2000,7(12):969-977
BACKGROUND: The committed step in the biosynthesis of the anticancer drug taxol in yew (Taxus) species is the cyclization of geranylgeranyl diphosphate to taxa-4(5),11(12)-diene. The enzyme taxadiene synthase catalyzes this complex olefin cation cyclization cascade involving the formation of three rings and three stereogenic centers. RESULTS: Recombinant taxadiene synthase was incubated with specifically deuterated substrates, and the mechanism of cyclization was probed using MS and NMR analyses of the products to define the crucial hydrogen migration and terminating deprotonation steps. The electrophilic cyclization involves the ionization of the diphosphate with closure of the A-ring, followed by a unique intramolecular transfer of the C11 proton to the re-face of C7 to promote closure of the B/C-ring juncture, and cascade termination by proton elimination from the beta-face of C5. CONCLUSIONS: These findings provide insight into the molecular architecture of the first dedicated step of taxol biosynthesis that creates the taxane carbon skeleton, and they have broad implications for the general mechanistic capability of the large family of terpenoid cyclization enzymes. 相似文献
2.
Masayuki Utsugi 《Tetrahedron letters》2007,48(39):6868-6872
Construction of the taxane skeleton via the stereoselective conjugate addition of cyanide and the intramolecular B-alkyl Suzuki-Miyaura coupling reaction is described. A conjugate addition of cyanide to enone 17 proceeded diastereoselectively to provide the desired 18 incorporating the correct C3 stereogenic center in the taxol C-ring. The intramolecular B-alkyl Suzuki-Miyaura coupling reaction of 22, which was derived from 18, successfully furnished the taxol B-ring in 81% yield. 相似文献
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Ma C Schiltz S Le Goff XF Prunet J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(24):7314-7323
BC ring-systems of taxol with different or no protecting group for the C1,C2-diol moiety have been efficiently synthesized. The eight-membered B ring is formed by a ring-closing metathesis reaction (RCM) between the C10 and C11 carbon atoms. The influence of the 1,2-diol protecting group on the RCM reaction has been studied in detail. 相似文献
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抗癌药物紫杉醇的全合成-Nicolaou法合合成紫杉醇的剖析 总被引:2,自引:0,他引:2
介绍和剖析了用Micolaou法全合成紫杉醇的方法,包括合成的战略和路线,关键反应和保护基的应用等。 相似文献
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Thomas D. McClure Karl H. Schram Mark L. J. Reimer 《Journal of the American Society for Mass Spectrometry》1992,3(6):672-679
The antitumor agent taxol has been examined by electron ionization, chemical ionization, and fast atom bombardment mass spectrometry. Three ion series are observed: (1) the M-series, characteristic of the intact molecule; (2) the T-series, with fragments derived from the taxane ring; and (3) the S-series representing the C-13 side chain. Neutral losses dominate each series of ions and serve to verify the presence and number of functionalities in each portion of the molecule. Fragmentation pathways and mechanisms of ion formation are proposed on the basis of product ion analysis and accurate mass measurements. 相似文献
9.
《Journal of organometallic chemistry》2006,691(24-25):5438-5443
Model BC ring-systems of taxol 23b and 28b, which lack an oxygenated substituent at C7, have been efficiently synthesized. The key step is a ring-closing metathesis (RCM) to form the 8-membered B ring between C10 and C11. Comparison of the metathesis reaction in this route with the RCM used in a previous study with similar substrates is highlighted. 相似文献
10.
Coupling-ready aminated side chain analog precursors of the anticancer drug taxol were prepared through the β-lactam synthon method. The procedure described represents an easy connection between β-lactams and 2,3-diamino acids, is highly stereospecific, and causes no racemization due to vicinal group participation. 相似文献
11.
The taxol side chain (S(R),2R,3S)-N-tert-butanesulfinyl-O-Boc-3-phenylisoserine benzyl ester 4c was synthesized through a lithium enolate addition of O-Boc-alpha-hydroxyacetate benzyl ester 5c to benzylidene (S(R))-tert-butanesulfinamide 6a in excellent yield and diastereoselectivity. By similar approach, a series of enantiopure 3-substituted isoserine benzyl esters 4 useful for the semi-syntheses of taxol derivatives were also prepared in high to excellent yields and diastereoselectivities. The diastereoselective addition mechanism was discussed on the basis of the experimental observation. 相似文献
12.
The first oxygenation step in the biosynthesis of the anticancer drug taxol in Taxus species is the cytochrome p450-mediated hydroxylation (with double bond migration) of the diterpene olefin precursor taxa-4(5),11(12)-diene to taxa-4(20),11(12)-dien-5alpha-ol. A homology-based cloning strategy, employing an induced Taxus cell library, yielded a cDNA encoding taxadiene 5alpha-hydroxylase, which was functionally expressed in yeast and insect cells. The recombinant enzyme was characterized and shown to efficiently utilize both taxa-4(5),11(12)-diene and taxa-4(20),11(12)-diene (as an adventitious substrate) to synthesize taxa-4(20),11(12)-dien-5alpha-ol. This hydroxylase resembles, in sequence and properties, other cytochrome p450 oxygenases of taxol biosynthesis. The utilization of both taxadiene isomers in the formation of taxa-4(20),11(12)-dien-5alpha-ol is novel, suggesting a reaction mechanism involving promiscuous radical abstraction with selective oxygen insertion rather than epoxidation of the C4,C5-alkene of the natural substrate and allylic rearrangement of the resulting taxa-11(12)-en-4,5epoxide. 相似文献
13.
Veronika N meth-Kiss Esther Forg cs Tibor Cserh ti G bor Schmidt 《Journal of chromatography. A》1996,750(1-2):253-256
The influence of a vegetative period on the taxol content in the needles of Taxus brevifolia grown in Hungary was determined using porous graphitized carbon column and a HPLC-diode array detection system. The relative standard deviation of the retention time of taxol peak was 1.24%, the peak symmetry 1.06–1.07 indicating the reliability of the HPLC systems. It was found that the accuracy of the peak purity test can be enhanced by carrying out the test at various wavelengths. It was established that the taxol content is considerably higher in the winter months and taqxol is purer in the same period. Taxol content also depends on the production site and taxol exctracted from the foliage contains more taxoteres than taxol extracted from bark. 相似文献
14.
An analytical method for the determination of taxol (paclitaxel) via cathodic stripping square wave voltammetry has been developed. The method allows to achieve a detection limit of 5.2 ng ml−1 and a determination limit of 11.0 ng ml−1 working with a mercury drop electrode in 0.05 M boric acid/borate buffer pH 9.0, previously accumulated at −0.1 V (v.s. Ag/AgCl/KCl 3 M) for 360 s. Moreover, information about the mechanisms governing the reduction of taxol has been obtained from the studies of the instrumental parameters of square wave voltammetry technique. After addition of an internal standard, taxol was extracted from spiked human urine and the proposed method was successfully applied to the quantification of the analyte. 相似文献
15.
《Tetrahedron letters》1988,29(12):1367-1370
The type 2 intramolecular Diels-Alder reaction is utilized to assemble a taxol precursor. 相似文献
16.
Taxol is an important anticancer drug used widely in the clinical field. In this study, some endophytic fungi were isolated from selected medicinal plants, and were screened for their potential in the production of taxol, using a rapid separation technique of high performance thin layer chromatography (HPTLC). Of the 20 screened fungi, only 13 fungal species produced taxol in the artificial culture medium. The results of HPTLC showed that the 13 fungal species had identical ultraviolet (UV) characteristics, positive reactivity with a spray reagent, yielding a blue spot, which turned to dark gray after 24 hours, and had Rf values identical to that of the authentic taxol. The amount of taxol was also quantified by comparing the peak area and the peak height of the fungal samples with those of authentic taxol. 相似文献
17.
Dmitry Gorbachev Elliot Smith Dr. Stephen P. Argent Dr. Graham N. Newton Prof. Hon Wai Lam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(50):e202201478
The synthesis of new morphinan opioids by the addition of photochemically generated carbon-centered radicals to substrates containing an enone in the morphinan C-ring, is described. Using tetrabutylammonium decatungstate (TBADT) as a hydrogen atom transfer photocatalyst, diverse radical donors can be used to prepare a variety of C8-functionalized morphinan opioids. This work demonstrates the late-stage modification of complex, highly functionalized substrates. 相似文献
18.
[structure: see text] A flexible and efficient procedure has been developed for the conjugation of taxol to various arginine-based molecular transporters via the taxol C2' O-chloroacetyl derivative. The resultant taxol-transporter conjugates are highly water soluble and release free taxol with half-lives of minutes to hours depending on the pH and the linker structure. 相似文献
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Summary Extracts fromTaxus species needles (T. media, T. baccata, T. cuspidata) were separated on thin layers of silica Si 60 by two-stage development (first stage: 60 % heptane solution of a mixture
of 5% methanol and 95% chloroform; second stage: 70% heptane solution of the same solution of methanol in chloroform). The
peak of taxol was satisfactorily separated from the neighbouring peaks to permit its densitometric determination. Content
of taxol for various samples of Taxus species is compared. 相似文献
20.
Summary Extracts fromTaxus species needles (T. media, T. baccata, T. cuspidata) were separated on thin layers of silica Si 60 by two-stage development (first stage: 60 % heptane solution of a mixture
of 5 % methanol and 95 % chloroform; second stage: 70 % heptane solution of the same solution of methanol in chloroform).
The peak of taxol was satisfactorily separated from the neighbouring peaks to permit its densitometric determination. Content
of taxol for various samples of Taxus species is compared. 相似文献