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1.
A highly stereoselective route to the polysubstituted chiral octahydrobenzofuran 12 , a potential synthon for the E‐ring core in the (?)‐reserpine synthesis, is described. The α‐bromo acetal 11 was obtained from inexpensive (?)‐shikimic acid ( 3 ) through a series of highly stereoselective chemical reactions (Scheme). Et3B/Bu3SnH‐Mediated intramolecular radical cyclization of 11 led to compound 12 with the required configuration. 相似文献
2.
《Journal of heterocyclic chemistry》2018,55(9):2055-2060
A straightforward approach for the regioselective synthesis of highly functionalized pyrazolo[5,1‐b]purine from the annulation of 6‐bromo‐3‐cyano‐2‐(ethylthio)‐5‐methyl‐7‐oxo‐6,7‐dihydropyrazolo[1,5‐a]pyrimidine with thiourea as a bisnucleophilic reagent under reflux condition in CH3CN in the presence of Et3N has been developed. The N‐alkylation of the synthesis compound was also accomplished. The true regioisomer was determined by 2D‐NOESY NMR spectroscopy, as well. 相似文献
3.
Highly Enantioselective Tandem Michael Addition of Tryptamine‐Derived Oxindoles to Alkynones: Concise Synthesis of Strychnos Alkaloids
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Weigang He Jiadong Hu Pengyan Wang Le Chen Kai Ji Siyu Yang Yin Li Zhilong Xie Prof. Dr. Weiqing Xie 《Angewandte Chemie (International ed. in English)》2018,57(14):3806-3809
A highly enantioselective tandem Michael addition of tryptamine‐derived oxindoles to alkynones was developed by taking advantage of a chiral N,N′‐dioxide Sc(OTf)3 catalyst. The reaction enables the facile preparation of enantioenriched spiro[pyrrolidine‐3,3′‐oxindole] compounds, which provides a novel strategy for the synthesis of monoterpenoid indole alkaloids. As a demonstration, the asymmetric synthesis of strychnos alkaloids [(?)‐tubifoline, (?)‐tubifolidine, (?)‐dehydrotubifoline] was achieved in 10–11 steps. 相似文献
4.
Bo Xu Bingyang Wang Wen Xun Fayang G. Qiu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5810-5813
A concise and highly stereoselective total synthesis of the Daphniphyllum alkaloids (?)‐daphenylline has been accomplished. The synthesis was started from (S)‐carvone and proceeded via a stereoselective Mg(ClO4)2‐catalyzed intramolecular amide addition cyclization, an intramolecular Diels–Alder reaction to construct the ABCD tetracyclic core architecture, and a Robinson annulation coupled with an oxidative aromatization sequence. Finally, the DF ring system was installed through an intramolecular Friedel–Crafts cyclization. The total synthesis of (?)‐daphenylline is achieved in 19 steps in the longest reaction sequence and in 7.6 % overall yield. 相似文献
5.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16121-16125
Highly enantioselective gold‐catalyzed intramolecular cyclization of N‐allenamides was implemented by utilizing a designed chiral sulfinamide phosphine ligand (PC‐Phos). This represents the first example of highly enantioselective intramolecular cyclization of N‐allenamides. The practicality of this reaction was validated in the total synthesis of (R )‐desbromoarborescidine A and formal synthesis of (R )‐desbromoarborescidine C and (R )‐deplancheine. Moreover, the catalyst system PC‐Phos/AuNTf2 proved to be specifically efficient to promote the desymmetrization of N‐allenamides in excellent yields with satisfactory ee values. 相似文献
6.
Chiral Ammonium Betaine‐Catalyzed Highly Stereoselective Aza‐Henry Reaction of α‐Aryl Nitromethanes with Aromatic N‐Boc Imines
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Dr. Daisuke Uraguchi Keigo Oyaizu Haruhiro Noguchi Prof. Dr. Takashi Ooi 《化学:亚洲杂志》2015,10(2):334-337
A highly stereoselective aza‐Henry reaction of α‐aryl nitromethanes with aromatic N‐Boc imines was established by using C1‐symmetric chiral ammonium betaine as a bifunctional organic base catalyst. Various substituted aryl groups for both imines and nitromethanes were tolerated in the reaction, and a series of precursors for the synthesis of unsymmetrical anti‐1,2‐diaryl ethylenediamines was provided. 相似文献
7.
Asymmetric Total Synthesis of (−)‐Englerin A through Catalytic Diastereo‐ and Enantioselective Carbonyl Ylide Cycloaddition
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Dr. Taiki Hanari Dr. Naoyuki Shimada Dr. Yasunobu Kurosaki Dr. Neetipalli Thrimurtulu Dr. Hisanori Nambu Dr. Masahiro Anada Prof. Dr. Shunichi Hashimoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(33):11671-11676
An asymmetric total synthesis of the guaiane sesquiterpene (?)‐englerin A, a potent and selective inhibitor of the growth of renal cancer cell lines, was accomplished. The basis of the approach is a highly diastereo‐ and enantioselective carbonyl ylide cycloaddition with an ethyl vinyl ether dipolarophile under catalysis by dirhodium(II) tetrakis[N‐tetrachlorophthaloyl‐(S)‐tert‐leucinate], [Rh2(S‐TCPTTL)4], to construct the oxabicyclo[3.2.1]octane framework with concomitant introduction of the oxygen substituent at C9 on the exo‐face. Another notable feature of the synthesis is ruthenium tetraoxide‐catalyzed chemoselective oxidative conversion of C9 ethyl ether to C9 acetate. 相似文献
8.
Dr. Belén Vaz Leticia Otero Prof. Rosana Álvarez Prof. Ángel R. de Lera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(39):13065-13074
A new stereocontrolled total synthesis of the configurationally labile C37‐norcarotenoid pyrrhoxanthin in enantiopure form has been completed. A highly stereoselective Horner–Wadsworth–Emmons (HWE) condensation of a C17‐allylphosphonate and a C20‐aldehyde was used as the last conjunctive step. Both a Sonogashira reaction to form the C17‐phosphonate and the final HWE condensation proved to be compatible with the sensitive C7–C10 enyne E configuration. Regioselective (5‐exo‐dig) silver‐promoted lactonization reactions of three alternative pent‐2‐en‐4‐ynoic acid precursors with increased complexity, including a fully functionalized C20‐fragment, were explored for the preparation of the γ‐alkylidenebutenolide fragment. This survey extends the existing methodologies for the preparation of oxygen‐containing carotenoids (xanthophylls) and streamlines the synthesis of additional members of the C37‐norcarotenoid butenolide family of natural products. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(13):3444-3448
A nearly‐30‐year‐old unanswered synthetic puzzle, astellatol, has been solved in an enantiospecific manner. The highly congested pentacyclic skeleton of this rare sesterterpenoid, which possesses a unique bicyclo[4.1.1]octane motif, ten stereocenters, a cyclobutane that contains two quaternary centers, an exo‐methylene group, and a sterically encumbered isopropyl trans‐hydrindane motif, makes astellatol arguably one of the most challenging targets for sesterterpenoid synthesis. An intramolecular Pauson–Khand reaction was exploited to construct the right‐hand side scaffold of this sesterterpenoid. An unprecedented reductive radical 1,6‐addition, mediated by SmI2, forged the cyclobutane motif. Last, a strategic oxidation/reduction step provided not only the decisive solution for the remarkably challenging late‐stage transformations, but also a highly valuable unravelling of the notorious issue of trans‐hydrindane synthesis. Importantly, the synthesis of astellatol showcases a rapid, scalable strategy to access diverse complex isopropyl trans‐hydrindane sesterterpenoids. 相似文献
10.
Dr. Nan Zhao Dr. Shuqiang Yin Shengling Xie Dr. Hao Yan Pan Ren Gui Chen Fang Chen Prof. Dr. Jing Xu 《Angewandte Chemie (International ed. in English)》2018,57(13):3386-3390
A nearly‐30‐year‐old unanswered synthetic puzzle, astellatol, has been solved in an enantiospecific manner. The highly congested pentacyclic skeleton of this rare sesterterpenoid, which possesses a unique bicyclo[4.1.1]octane motif, ten stereocenters, a cyclobutane that contains two quaternary centers, an exo‐methylene group, and a sterically encumbered isopropyl trans‐hydrindane motif, makes astellatol arguably one of the most challenging targets for sesterterpenoid synthesis. An intramolecular Pauson–Khand reaction was exploited to construct the right‐hand side scaffold of this sesterterpenoid. An unprecedented reductive radical 1,6‐addition, mediated by SmI2, forged the cyclobutane motif. Last, a strategic oxidation/reduction step provided not only the decisive solution for the remarkably challenging late‐stage transformations, but also a highly valuable unravelling of the notorious issue of trans‐hydrindane synthesis. Importantly, the synthesis of astellatol showcases a rapid, scalable strategy to access diverse complex isopropyl trans‐hydrindane sesterterpenoids. 相似文献
11.
Directed Remote Lateral Metalation: Highly Substituted 2‐Naphthols and BINOLs by In Situ Generation of a Directing Group
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Dr. Jignesh J. Patel Dr. Marju Laars Dr. Wei Gan Dr. Johnathan Board Dr. Matthew O. Kitching Prof. Victor Snieckus 《Angewandte Chemie (International ed. in English)》2018,57(30):9425-9429
A general synthesis of highly substituted 2‐naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with either LiNEt2 or LiNiPr2 into Z‐cinnamamides, thus generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation for ring closure to give the aryl 2‐naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one‐pot process. Mechanistic insight into the remote lateral metalation step, demonstrating the requirement of Z‐cinnamamide, is described. Application of this methodology to the synthesis of highly substituted 3,3′‐diaryl BINOL ligands is also reported. 相似文献
12.
Dasireddi Chandra Rao Vanam Shekhar Dorigondla Kumar Reddy Baggu Chinnababu Yenamandra Venkateswarlu 《Helvetica chimica acta》2013,96(12):2179-2184
A simple and highly concise strategy has been developed for the stereoselective total synthesis of leiocarpin C starting from commercially available mandelic ester. The strategy utilizes the OsO4‐catalyzed cis‐hydroxylation and selective reduction with K‐Selectride as key steps. 相似文献
13.
Efficient Synthesis of Tetrahydroquinolines from the Reaction of Aldehyde,Aniline, and Alkene under the In Situ Redox of SnCl2 and FeCl3
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Qiaoxia Guo Weiling Teng Shenyong Ren Shasha Rao Yanqing Wang Liwei Chen Baojian Shen Tamotsu Takahashi 《Journal of heterocyclic chemistry》2014,51(4):1100-1105
A highly efficient three‐component Povarov reaction for the synthesis of tetrahydroquinoline derivatives was reported. The reaction of aldehyde, aniline, and alkene was carried out in the presence of Sn(IV), which was generated in situ from the redox reaction of SnCl2 and FeCl3, to afford tetrahydroquinoline derivatives in good to excellent yields. This discovery showed a sharp difference from the direct use of unstable SnCl4. Both aliphatic and aromatic aldehydes could be applied for the synthesis of the heterocycle in the reaction. The structure of the product 6‐chloro‐4‐methyl‐4‐neopentyl‐2‐propyltetrahydroquinoline and 6‐bromo‐4‐methyl‐4‐neopentyl‐2‐propyltetrahydroquinoline was confirmed by X‐ray diffraction analysis. 相似文献
14.
One‐Pot Synthesis of O‐Allylhydroxylamines through the Organocatalytic Oxidation of Tertiary Allylic Amines Followed by a [2,3]‐Meisenheimer Rearrangement
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Alexis Theodorou Dr. Dimitris Limnios Prof. Dr. Christoforos G. Kokotos 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5238-5241
A cheap, green, and highly efficient one‐pot method for the synthesis of O‐protected allylic alcohols is described. By utilizing 2,2,2‐trifluoroacetophenone as the organocatalyst and H2O2 as the oxidant, a variety of allylic amine N‐oxides were synthesized, which upon heating are converted to the final products through a [2,3]‐Meisenheimer rearrangement. 相似文献
15.
Dr. Sophie Colombel Dr. Nathalie Van Hijfte Dr. Thomas Poisson Dr. Eric Leclerc Prof. Dr. Xavier Pannecoucke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12778-12787
A new method for the synthesis of fluorinated α‐C‐glycosides is described. The reactions between highly electrophilic radicals (fluorinated or unfluorinated) and a 2‐benzyloxyglucal or galactal provide 2‐keto‐D ‐arabino‐ or 2‐keto‐D ‐lyxo‐hexopyranosides through an addition/fragmentation process. Sodium borohydride mediated or Meerwein–Ponndorf–Verley (MPV) reduction of these compounds provides α‐C‐glycosides that feature appropriate anchoring groups for further synthetic elaboration. The presence of CF2CO2iPr or CF2Br groups at the pseudo‐anomeric position allows efficient reduction/olefination or Br/Li‐exchange/nucleophilic‐addition sequences. These transformations open the way for the synthesis of fluorinated C‐glycosidic analogues of glycoconjugates. 相似文献
16.
《Journal of heterocyclic chemistry》2017,54(2):1054-1064
A concise one‐step procedure was developed for the synthesis of some newer tetrahydro‐4H‐benzo[1,3‐e ]oxazines and β‐acylamino ketone derivatives via condensation of cyclohexanone derivative with different aromatic aldehydes and nitriles in the presence of tetrachlorosilane/zinc chloride (TCS/ZnCl2) reagent mixture under ambient conditions. Docking studies for the synthesized benzo‐oxazine derivatives were designed and a model of highly active derivatives was mapped for the antimicrobial screening. 相似文献
17.
Songwen Xie Yuqing Hou Cal Y. Meyers Paul D. Robinson 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):o159-o161
The title compound, C12H20O3, (IV), the ethyl ester of which is an intermediate in the synthesis of a compound reported to be highly estrogenic, has been prepared. After the initial steps reported for the synthesis of this ester intermediate were followed, it was converted into the crystalline acid, (IV), for X‐ray analysis. It was verified that (IV) was racemic when prepared. X‐ray analysis showed that anti‐hydrogenation of the double bond had occurred in the synthesis, making the orientation of the carboxyl group cis to the 2‐methyl group and trans to the 3‐ethyl group. NMR spectroscopy showed that the stereochemistry of (IV) was identical with that of its ester precursor. While the earlier report did not note the stereochemistry of this ester, it pointed out that the estrogenic product derived from it possessed the opposite carboxyl‐2‐methyl orientation, i.e.trans, although no X‐ray analysis was performed. In the light of these results and the importance of correlating biological activity with compound structure, the unequivocal characterization of the highly estrogenic compound is warranted. 相似文献
18.
As alternatives to the common tertiary phosphine/Pd systems, well‐defined N‐heterocyclic carbene–Pd complexes have been proven to be highly efficient precatalysts for intermolecular direct annalution of o‐haloanilines and ketones at lower catalyst loadings. A highly efficient and practical protocol for synthesis of functionalized indoles was developed using (IPr)Pd(acac)Cl as catalyst. Both o‐bromoanilines and o‐chloroanilines gave rise to efficient coupling under the reaction conditions. Related to acyclic ones, cyclic ketones coupled more effectively with o‐haloanilines. With [Pd(IPr)2] as catalyst, the base‐sensitive groups including OH and CO2H groups could be tolerated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
19.
A concise and convergent total synthesis of the highly cytotoxic marine natural product apratoxin A is accomplished by an 18‐step linear sequence. The high sensitivity of the thiazoline, bearing an adjacent β‐hydroxyl group at the C35‐position, results in the assembly process requiring the inclusion of appropriate protecting groups and the careful optimization of all individual transformations. In the synthesis of 3,7‐dihydroxy‐2,5,8,8‐tetramethylnonanoic acid (Dtena), the three reagent‐controlled asymmetric reactions enables us to introduce four chiral carbon centers in a dihydroxylated fatty acid moiety. Formation of the hindered ester and sterically‐unfavorable N‐methylamide bonds were successfully demonstrated. The thiazoline in apratoxin A was constructed by Tf2O and Ph3PO‐mediated dehydrative cyclization, and final macrocyclization was achieved between N‐methylisoleucine and proline residues. Moreover, an oxazoline analogue and a C34 epimer of apratoxin A have also been elaborated in a similar approach. This synthetic route would enable assembly of other analogues differing in stereocenters of Dtena and their amino acids. 相似文献
20.
Catalytic Michael/Ring‐Closure Reaction of α,β‐Unsaturated Pyrazoleamides with Amidomalonates: Asymmetric Synthesis of (−)‐Paroxetine
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Yu Zhang Yuting Liao Prof. Dr. Xiaohua Liu Qian Yao Yuhang Zhou Dr. Lili Lin Prof. Dr. Xiaoming Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(42):15119-15124
A highly enantioselective tandem Michael/ring‐closure reaction of α,β‐unsaturated pyrazoleamides and amidomalonates has been accomplished in the presence of a chiral N,N′‐dioxide–Yb(OTf)3 complex (Tf: trifluoromethanesulfonyl) to give various substituted chiral glutarimides with high yields and diastereo‐ and enantioselectivities. Moreover, this methodology could be used for gram‐scale manipulation and was successfully applied to the synthesis of (?)‐paroxetine. Further nonlinear and HRMS studies revealed that the real catalytically active species was a monomeric L ‐PMe2 –Yb3+ complex. A plausible transition state was proposed to explain the origin of the asymmetric induction. 相似文献