共查询到20条相似文献,搜索用时 78 毫秒
1.
Ronald Nelson Moiss Gulías Jos L. Mascareas Fernando Lpez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(46):14571-14575
A practical synthesis of (−)‐englerin A was accomplished in 17 steps and 11 % global yield from commercially available achiral precursors. The key step consists of a platinum‐catalyzed [4C+3C] allenediene cycloaddition that directly delivers the trans‐fused guaiane skeleton with complete diastereoselectivity. The high enantioselectivity (99 % ee) stems from an asymmetric ruthenium‐catalyzed transfer hydrogenation of a readily assembled diene–ynone. The synthesis also features a highly stereoselective oxygenation, and a late‐stage cuprate alkylation that enables the preparation of previously inaccessible structural analogues. 相似文献
2.
Debendra K. Mohapatra Dr. Pragna P. Das Manas Ranjan Pattanayak J. S. Yadav Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(7):2072-2078
A novel iodine‐catalyzed highly diastereoselective synthesis of trans‐2,6‐disubstituted‐3,4‐dihydropyrans have been achieved from δ‐hydroxy α,β‐unsaturated aldehydes by treating with allyltrimethyl silane in THF at room temperature with good to excellent yields. This methodology has been successfully implemented for a concise asymmetric synthesis of C28–C37 dioxabicyclo[3.2.1]octane ring system of (+)‐sorangicin A in 8 steps with 21 % overall yield. 相似文献
3.
Lipase‐Catalyzed Dynamic Kinetic Resolution of C1‐ and C2‐Symmetric Racemic Axially Chiral 2,2′‐Dihydroxy‐1,1′‐biaryls
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Gamal A. I. Moustafa Yasuhiro Oki Prof. Dr. Shuji Akai 《Angewandte Chemie (International ed. in English)》2018,57(32):10278-10282
We have discovered that the racemization of configurationally stable, axially chiral 2,2′‐dihydroxy‐1,1′‐biaryls proceeds with a catalytic amount of a cyclopentadienylruthenium(II) complex at 35–50 °C. Combining this racemization procedure with lipase‐catalyzed kinetic resolution led to the first lipase/metal‐integrated dynamic kinetic resolution of racemic axially chiral biaryl compounds. The method was applied to the synthesis of various enantio‐enriched C1‐ and C2‐symmetric biaryl diols in yields of up to 98 % and enantiomeric excesses of up to 98 %, which paves the way for new developments in the field of asymmetric synthesis. 相似文献
4.
Novel and Stereospecific Synthesis of (2S)‐3‐(2,4,5‐Trifluorophenyl)propane‐1,2‐diol from D‐Mannitol
下载免费PDF全文
![点击此处可从《Helvetica chimica acta》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Derya Aktaş Meryem Fıstıkçı Özlem Gündoğdu Hasan Seçen M. Fethi Şahin Ramazan Altundaş Yunus Kara 《Helvetica chimica acta》2015,98(8):1127-1131
A stereospecific synthesis of (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph3P catalyzed reaction of the latter with C2Cl6 followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield. 相似文献
5.
Eric E. Boros Istvan Kaldor Philip S. Turnbull 《Journal of heterocyclic chemistry》2011,48(3):733-736
2‐Methyl‐4‐(trifluoromethyl)‐1H‐indole‐5‐carbonitrile is a key intermediate in the synthesis of selective androgen receptor modulators discovered in these laboratories. A practical and convergent synthesis of the title compound starting from 4‐nitro‐3‐(trifluoromethyl)phenol and tert‐butyl acetoacetate was developed, including a telescoped procedure for synthesis (without isolation) and Nenitzescu reaction of 2‐trifluoromethyl‐1,4‐benzoquinone. Conversion of the known Nenitzescu indole product to a novel triflate intermediate followed by palladium‐catalyzed cyanation afforded a penultimate carbonitrile. Removal of the C‐3 tert‐butyl ester group on the indole through a decarboxylative pathway completed the synthesis of the title compound in six steps (27% overall yield) from 4‐nitro‐3‐(trifluoromethyl)phenol (five steps, 37% overall yield from tert‐butyl acetoacetate). J. Heterocyclic Chem., (2011). 相似文献
6.
Diego M. Carballa Antonio Rumbo Mercedes Torneiro Miguel Maestro Antonio Mouriño 《Helvetica chimica acta》2012,95(10):1842-1850
A convergent synthesis of an analogue of (1α)‐1,25‐dihydroxyvitamin D3 ( 1b ) with a C7 side chain at C(12), i.e., of 5 (Fig.), is described. A key step of the synthesis is the assembly of the triene system by a PdII‐catalyzed ring closure of an enol triflate (‘bottom’ fragment) followed by coupling of the resulting PdII intermediate with an alkenylboronate (‘upper’ fragment) (Scheme 2). The synthetic strategy allows isotopic labelling at the end of the synthesis. 相似文献
7.
Schisandraceae triterpenoids are novel natural products that contain highly fused ring systems bearing multiple chiral centers surrounding. Some of them exhibit promising bioactivities, such as antitumor, anti‐HIV, etc. In this article, we describe our efforts to the collective total synthesis of schilancidilactones A, B, schilancitrilactones A, B, C, and 20‐epi‐schilancitrilactone A from common precursors. An intramolecular radical cyclization, late‐stage halogenation and AIBN‐mediated or Ni‐catalyzed intermolecular radical cross coupling reaction were employed as the key steps. 相似文献
8.
Cu‐Catalyzed Aerobic Oxidative Cyclizations of 3‐N‐Hydroxyamino‐1,2‐propadienes with Alcohols,Thiols, and Amines To Form α‐O‐, S‐, and N‐Substituted 4‐Methylquinoline Derivatives
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pankaj Sharma Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4590-4594
A one‐pot, two‐step synthesis of α‐O‐, S‐, and N‐substituted 4‐methylquinoline derivatives through Cu‐catalyzed aerobic oxidations of N‐hydroxyaminoallenes with alcohols, thiols, and amines is described. This reaction sequence involves an initial oxidation of N‐hydroxyaminoallenes with NuH (Nu=OH, OR, NHR, and SR) to form 3‐substituted 2‐en‐1‐ones, followed by Brønsted acid catalyzed intramolecular cyclizations of the resulting products. Our mechanistic analysis suggests that the reactions proceed through a radical‐type mechanism rather than a typical nitrone‐intermediate route. The utility of this new Cu‐catalyzed reaction is shown by its applicability to the synthesis of several 2‐amino‐4‐methylquinoline derivatives, which are known to be key precursors to several bioactive molecules. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(12):3382-3386
An asymmetric synthesis of C 3‐symmetric triangular macrocycles is reported. 1‐Methylsulfonyl‐4‐(4‐vinylphenyl)‐1,2,3‐triazole undergoes a rhodium(II)‐catalyzed cyclotrimerization to establish an enantiopure C 3‐symmetric triangular macrocycle motif. This method can be applied to the synthesis of an enantiopure hydrocarbon, which owes its chirality to asymmetric distribution of H/D atoms on the benzene rings. 相似文献
10.
Dokuburra Chanti Babu Kankati Ashalatha Chitturi Bhujanga Rao Jon Paul Selvam Jondoss Yenamandra Venkateswarlu 《Helvetica chimica acta》2011,94(12):2215-2220
An efficient and short total synthesis of (?)‐cleistenolide ( 1 ) from D ‐mannitol with an overall yield of 23.6% is described. The chiron approach for the synthesis of (?)‐cleistenolide involves a one‐C‐atom Wittig olefination, a selective allylic triethylsilyl protection, and a Grubbs‐catalyzed ring‐closure‐metathesis (RCM) reaction as the key steps. 相似文献
11.
Dr. Rajavel Srinivasan Dr. Anthony G. Coyne Prof. Dr. Chris Abell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11680-11684
A one‐pot protocol for the synthesis of N‐aryl 1,2,3‐triazoles from arenes by an iridium‐catalyzed C?H borylation/copper catalyzed azidation/click sequence is described. 1 mol % of Cu(OTf)2 was found to efficiently catalyze both the azidation and the click reaction. The applicability of this method is demonstrated by the late‐stage chemoselective installation of 1,2,3‐triazole moiety into unactivated molecules of pharmaceutical importance. 相似文献
12.
Michael Z. Liang Simon J. Meek 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14372-14377
A catalytic enantioselective method for the synthesis of 1,4‐keto‐alkenylboronate esters by a rhodium‐catalyzed conjugate addition pathway is disclosed. A variety of novel, bench‐stable alkenyl gem‐diboronate esters are synthesized. These easily accessible reagents react smoothly with a collection of cyclic α,β‐unsaturated ketones, generating a new C?C bond and stereocenter. Products are isolated in up to 99 % yield with greater than 20:1 E/Z and greater than 99:1 e.r. Mechanistic studies show the site‐selectivity of transmetalation and reactivity is ligand dependent. The utility of the approach is highlighted by gram‐scale synthesis of enantioenriched cyclic 1,4‐diketones, and stereoselective transformations of the products by hydrogenation, allylation, and isomerization. 相似文献
13.
Benedict's solution/ vitamin C: An alternative catalytic protocol for the synthesis of regioselective‐1,4‐disubstituted‐1H‐1,2,3‐triazoles at room temperature
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Manashjyoti Konwar Roktopol Hazarika Abdul A. Ali Mitali Chetia Nageshwar D. Khupse Prakash J. Saikia Diganta Sarma 《应用有机金属化学》2018,32(8)
A novel and highly efficient method for the synthesis of 1,4‐disubstituted‐1H‐1,2,3‐triazoles by copper‐catalyzed azide‐alkyne cycloaddition has been developed. This economic and sustainable protocol uses a readily available Benedict's solution/Vitamin C catalyst system affording a wide range of 1,4‐disubstituted‐1H‐1,2,3‐triazoles under mild conditions. 相似文献
14.
1‐Butyl‐3‐methyl Imidazolium Acetate Catalyzed Synthesis of N‐substituted‐5‐arylidene‐rhodanines
下载免费PDF全文
![点击此处可从《Journal of heterocyclic chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Sarangthem Joychandra Singh Sohail Ahmad S. M. S. Chauhan 《Journal of heterocyclic chemistry》2014,51(Z1):E129-E139
A direct method for the synthesis of N‐substituted‐5‐arylidene‐rhodanines has been reported in high yield via [bmim]OAc‐catalyzed one‐pot four‐component domino Knoevenagel condensation of primary amine, carbon disulfide, ethyl chloroacetate, and aromatic aldehyde under neat condition. The catalytic role of [bmim]OAc is due to the acidic nature of C‐2 hydrogen of bmim cation and the basic nature of acetate anion in the noncovalent interactions. The synthetic methodology is simple and offers a wide scope for the synthesis of N‐substituted‐5‐arylidene‐rhodanines. 相似文献
15.
Total Syntheses of (+)‐Grandilodine C and (+)‐Lapidilectine B and Determination of their Absolute Stereochemistry
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Masaya Nakajima Prof. Dr. Shigeru Arai Prof. Dr. Atsushi Nishida 《Angewandte Chemie (International ed. in English)》2016,55(10):3473-3476
Enantioselective total syntheses of the Kopsia alkaloids (+)‐grandilodine C and (+)‐lapidilectine B were accomplished. A key intermediate, spirodiketone, was synthesized in 3 steps and converted into the chiral enone by enantioselective deprotonation followed by oxidation with up to 76 % ee. Lactone formation was achieved through stereoselective vinylation followed by allylation and ozonolysis. The total synthesis of (+)‐grandilodine C was achieved by palladium‐catalyzed intramolecular allylic amination and ring‐closing metathesis to give 8‐ and 5‐membered heterocycles, respectively. Selective reduction of a lactam carbonyl gave (+)‐lapidilectine B. The absolute stereochemistry of both natural products was thereby confirmed. These syntheses enable the scalable preparation of the above alkaloids for biological studies. 相似文献
16.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9335-9338
An enantioselective C−H addition to a C=C bond represents the most atom‐efficient route for the construction of chiral carbon–carbon skeletons, a central research topic in organic synthesis. We herein report the enantioselective yttrium‐catalyzed C(sp3)−H bond addition of 2‐methyl azaarenes, such as 2‐methyl pyridines, to various substituted cyclopropenes and norbornenes. This process efficiently afforded a new family of chiral pyridylmethyl‐functionalized cyclopropane and norbornane derivatives in high yields and high enantioselectivities (up to 97 % ee ). 相似文献
17.
Can Liu Tao Miao Lei Zhang Prof. Pinhua Li Yicheng Zhang Prof. Lei Wang 《化学:亚洲杂志》2014,9(9):2584-2589
A novel and efficient palladium‐catalyzed C2 arylation of N‐substituted indoles with 1‐aryltriazenes for the synthesis of 2‐arylindoles was developed. In the presence of BF3 ? OEt2 and palladium(II) acetate (Pd(OAc)2), N‐substituted indoles reacted with 1‐aryltriazenes in N,N‐dimethylacetamide (DMAC) to afford the corresponding aryl–indole‐type products in good to excellent yields. 相似文献
18.
Yoshihiko Yamamoto Prof. Dr. Ken Yamashita Tomitaka Hotta Toru Hashimoto Makoto Kikuchi Dr. Hisao Nishiyama Prof. Dr. 《化学:亚洲杂志》2007,2(11):1388-1399
Spirocyclic C‐arylglycosides were synthesized from the appropriately protected δ‐gluconolactones. Addition of lithium acetylide followed by glycosylation with 3‐(trimethylsilyl)propargyl alcohol converted the δ‐gluconolactones into silylated diynes. After desilylation, subsequent ruthenium‐catalyzed cycloaddition of the resultant diynes with alkynes or chloroacetonitrile gave spirocyclic C‐arylglycosides in good yields and selectivity. This strategy was also extended to the synthesis of spirocyclic C‐arylribosides from the known γ‐ribonolactone derivative. Moreover, silver‐catalyzed iodination of the sugar diynes followed by ruthenium‐catalyzed cycloaddition with acetylene delivered spirocyclic C‐iodophenylglycosides and ‐ribosides, which were subjected to palladium‐catalyzed C? C bond‐forming reactions and copper‐catalyzed coupling with nitrogen heterocycles to lead to various derivatives. 相似文献
19.
《化学:亚洲杂志》2017,12(15):1865-1868
A facile synthesis of 2‐amino‐1,3‐oxazoles via CuI‐catalyzed oxidative cyclization of enamines and N ,N ‐dialkyl formamides has been developed. The reaction proceeds through an oxidative C−N bond formation, followed by an intramolecular C(sp2)−H bond functionalization/C−O cyclization in one pot. This protocol provides direct access to useful 2‐amino‐1,3‐oxazoles and features protecting‐group‐free nitrogen sources, readily available starting materials, a broad substrate scope and mild reaction conditions. 相似文献
20.
2‐amino‐4‐oxo‐6‐substituted‐pyrrolo[2,3‐d]pynmidines as potential inhibitors of thymidylate synthase
Classical, antifolate inhibitors of thymidylate synthase often suffer from a number of potential disadvantages when used as antitumor agents. These include impaired uptake due to an alteration of the active transport system required for cellular uptake, as well as the formation of long acting, non‐effluxing polygluta‐mates via folypolyglutamate synthetase, which are responsible for toxicity to normal cells. To overcome some of the disadvantages of classical thymidylate synthase inhibitors, there has been considerable interest in the synthesis and evaluation of nonclassical inhibitors, which could enter cells via passive diffusion and are not substrates for folypolyglutamate synthetase. A series of eight nonclassical 6‐substituted 2‐amino‐4‐oxo‐pyrrolo[2,3‐d]pyrimidines 2a‐2h were designed as potential inhibitors of thymidylate synthase. The synthesis of the target compounds 2a‐2h was achieved via regioselective iodination at the 6‐position of 5 , palladium‐catalyzed coupling with the appropriate phenylacetylenes, reduction of the C8‐C9 triple bond followed by saponification. Preliminary biological results indicated that none of the target compounds showed inhibitory activities against thymidylate synthase from Escherichia coli, Lactobacillus casei, rat or human thymidylate synthase at the concentrations tested. None of the target compounds showed inhibitory activity against dihydrofolate reductase from Escherichia coli, Lactobacillus casei, rat or human at 3.0 × 10?5 M. However, 50% inhibition of dihydrofolate reductase from Pneumocystis carinii and from Toxoplasma gondii was achieved with compound 2d and with compound 2g at 3.0 × 10?5 M. 相似文献