Tetrahedron Letters

Editorial board ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30
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Graphical Contents List ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30
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Synthesis of 3-arylated indolines from dearomatization of indoles ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Natacha Denizot , Terry Tomakinian , Rodolphe Beaud , Cyrille Kouklovsky , Guillaume Vincent The introduction of aryl motifs at the C3-position of indole nuclei via dearomatization reactions has been the subject of intensive efforts in the last years and has culminated in several total syntheses of natural products. We provide in this digest Letter an overview of these recent advances including ours and we will highlight the fact that indoles could indeed act as nucleophiles but also as electrophiles and could be involved in radical reactions. Graphical abstract image
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Absolute configuration and anti-tumor activity of torrubiellin B ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Catalina Francis Pérez Hemphill , Georgios Daletos , Alexandra Hamacher , Matthias Ullrich Kassack , Wenhan Lin , Attila Mándi , Tibor Kurtán , Peter Proksch The dimeric anthracene derivative torrubiellin B (1) was isolated from the endophytic fungus Acremonium sp. that had been obtained from leaves of the Mangrove plant Sonneratia caseolaris. The absolute configuration of 1 was established as (5′R,10′S,10a′R) for the first time on the basis of its electronic circular dichroism (ECD) spectra aided with TDDFT-ECD calculations. Torrubiellin B (1) exhibited strong anti-tumor activity when tested in vitro against several solid cancer cell lines including cells that are resistant against the widely used cytostatic drug cisplatin. The IC50 values of 1 against cisplatin sensitive and cisplatin resistant cells were in the range of 0.2–2.6μM depending on cell line investigated. Graphical abstract image
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Efficient synthesis of a new bifunctional Cu(I) chelator ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Justin O. Massing , Roy P. Planalp Herein we report an efficient eight-step synthesis of N 1-(3-(methylthio)propyl)-2-((3-(methylthio)propyl)thio)benzene-1,4-diamine (1) from 6-nitrobenzo[d]thiazole. Incorporation of a nitro rather than a hydroxyl functionality off the aromatic ring serves to enhance conversion during thia- and aza-conjugate additions. Ultimate reduction of the nitro substituent affords a bifunctional Cu(I) chelate in gram-scale quantities for subsequent sensing applications. Graphical abstract image
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A rational eco-compatible design strategy for regio- and diastereoselective synthesis of novel dispiropyrrolidine/thiapyrrolizidine hybrids ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Anshu Dandia , Ruby Singh , Shahnawaz Khan , Sukhbeer Kumari , Pragya Soni A facile regio- and stereoselective synthesis of novel dispiroheterocyclic hybrids containing benzo[1,4]oxazine/benzo[1,4]thiazine and pyrrolidine/thiapyrrolizidine moieties via 1,3-dipolar cycloaddition reaction was carried out. The reaction has been carried out using 2,2,2-trifluoroethanol as a new alternative green solvent and catalyst for rapid access to construct a diversity-oriented library of regioselectivity dispiropyrrolidine/thiapyrrolizidines. Mild reaction conditions with excellent conversion, higher yields in shorter reaction times and the easy recyclability of 2,2,2-trifluoroethanol makes this protocol attractive, sustainable and environmentally benign. Graphical abstract image
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Synthesis of α-acylamino-amide-bis (indolyl) methane heterocycles by sequential one pot condensation-Ugi/Passerini reactions and their antimicrobial evaluation ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Gurpreet Kaur , Anitha Vadekeetil , Kusum Harjai , Vasundhara Singh New bis (indolyl) methane based heterocycles were developed by a proficient sequential synthesis in one pot where substituted aromatic aldehydes, isocyanides were varied, producing a library of benzamide and benzoate analogues with multiple points of diversity. The synthesized analogues were tested for their antibacterial potency against gram positive and gram negative pathogenic bacteria. Graphical abstract image
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Synthesis of 2,3-O-dibenzyl-6-O-sulfobutyl-α and β cyclodextrins: new chiral surfactants for capillary electrophoresis ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): James A. McKee , Thomas K. Green Amphiphilic sodium hexakis(2,3-O-dibenzyl-6-O-sulfobutyl)cyclomaltohexaose and sodium heptakis(2,3-O-dibenzyl-6-O-sulfobutyl)cyclomaltoheptaose were synthesized in four steps. Pyrene fluorescence studies indicate micelle formation at 90μM in water for both modified cyclodextrins (CDs). Both CDs offer potential as chiral micellar selectors for enantiomeric separations using capillary electrophoresis. Sodium heptakis(2,3-O-dibenzyl-6-O-sulfobutyl)cyclomaltoheptaose baseline resolved fluorescent cyanobenzylindole (CBI) derivatives of d/l-serine at concentrations of 50–200μM. Graphical abstract image
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The 15N induced isotope shift as an effective tool for the structure elucidation of 2,4 and 2,5 di-substituted thiazoles ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Tatiana Guzzo , Andrea Aramini , Samuele Lillini , Ridvan Nepravishta , Maurizio Paci , Alessandra Topai 15N isotope effects have been used for structural elucidation of the di-substituted thiazole 1-DFL 23805, a novel and potent dual CXCR1/CXCR2 inhibitor, developed by Dompé within the MedChem program. The compound and its 15N isotopologue have been synthesized according to the same proprietary procedure. The 1H and 13C NMR spectra have been measured. The isotope effects on chemical shifts and on coupling constants have been studied in detail. The collected data highlight a new perspective on the elucidation of disubstituted thiazole system, as only very few reference data have been published so far. All the results are consistent with the 2,4 regioisomery assignment. Graphical abstract image
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Facile synthesis of phthalocyanine at low temperature with diisopropylamide anion as nucleophile ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Wei Zheng , Cheng-Zhang Wan , Jing-Xuan Zhang , Cheng-Hui Li , Xiao-Zeng You Phthalocyanine has been synthesized from phthalonitrile and lithium diisopropylamide (LDA) at ambient or even lower temperatures. In this novel, facile, and low reactant-consuming method, diisopropylamide anions work as nucleophile to initiate the low temperature reaction. The mechanism has been rationalized by density functional theory (DFT) calculation. Our method is also useful for the transformation of some phthalonitrile derivatives to phthalocyanine compounds. Graphical abstract image
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Ligand-free C–C and C–N cross-couplings with Pd/Nf-G nanocomposite ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Radheshyam S. Shelkar , Suresh S. Shendage , Jayashree M. Nagarkar The catalytic activity of electrochemical deposited Pd nanoparticles on nafion–graphene support was examined for Buchwald–Hartwig amination reaction and Heck coupling reaction. The developed protocol is very efficient and ecofriendly, providing excellent product yield. The Pd/Nf-G catalyst can be used up to four cycles with slight decrease in catalytic activity. Graphical abstract image
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A two-step, one pot preparation of amines via acyl succinimides. Synthesis of the calcimimetic agents cinacalcet, NPS R-467, and NPS R-568 ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Cassie A. Gooodman , Elise Marie Janci , Olivia Onwodi , Chad C. Simpson , Christopher G. Hamaker , Shawn R. Hitchcock A method has been developed for the preparation of amines through a process of coupling acyl succinimides derived from commercially available carboxylic acids with amines to afford the corresponding amides. These amides are then reduced in situ with either diisobutylaluminum hydride or lithium aluminum hydride. The reaction tandem of the coupling reaction followed by the reduction affords the amine in fair to good yields after purification by flash chromatography. This one-pot, two reaction tandem process has been successfully applied to the synthesis of the calcimimetic agents cinacalcet, NPS R-467, and NPS R-568. Graphical abstract image
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Total synthesis of (±)-Anastatins A and B ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Guojun Pan , Yantao Ma , Ke Yang , Xia Zhao , Hui Yang , Qingwei Yao , Kui Lu , Tao Zhu , Peng Yu Two novel flavones (±)-Anastatins A and B, each containing a benzofuran moiety, were synthesized for the first time by using bromination, Suzuki coupling reaction, and an oxidation/Oxa-Michael reaction cascade as the key steps. The syntheses of (±)-Anastatins A and B were achieved in eight steps from the commercially available phloroglucinol with 9% and 10% overall yield, respectively. Graphical abstract image
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Synthesis of 4H-chromenes promoted by NbCl5 through multicomponent reaction ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Paula Beatriz Oshiro , Paula Souza da Silva Gomes Lima , Manoel Lima de Menezes , Luiz Carlos da Silva-Filho Multicomponent reactions between phenols, β-ketoesters, and benzaldehydes for the synthesis of 4H-chromenes derivatives promoted by niobium pentachloride (NbCl5) were carried out, providing good yields and reasonable reaction times under mild reaction conditions. Graphical abstract image
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Preparation of 1-tosyloxy-4-substituted-2-butenes using Ag(I) salts ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Jeffrey S. Stehouwer , Mark M. Goodman The trans-fluoro-2-butenyl group has been previously utilized as an N-substituent on several nortropanes for imaging the dopamine transporter with positron emission tomography. We report here a simplified and shorter synthesis of trans-1-tosyloxy-4-substituted-2-butenes using Ag(I) salts. This methodology was also applied to the synthesis of the cis-isomers. Furthermore, these procedures allow for the recovery of the majority of the Ag(I) ions. Graphical abstract image
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Pd(0)-catalyzed atom transfer radical cyclization of N-allyl-α-chloroamides: highly stereoselective synthesis of substituted γ-lactam ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Qiang Liu , Chen Chen , Xiaofeng Tong A catalysis system comprised of Pd(cod)Cl2 precursor and IMes ligand has been developed, which is efficient to catalyze the atom transfer radical cyclization of N-allyl-α-chloroamides with the help of NaI additive. This reaction provides a facile access to β-iodomethyl-γ-lactam with high stereoselectivity. Moreover, the results from the reaction of deuterium-labeled substrate and TEMPO-trapping experiment clearly indicate that radical intermediate(s) should be involved in the reaction. Graphical abstract image
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A practical synthesis of 5-functionalized thieno[2,3-d]pyrimidines ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Birgit Wilding , Stefan Faschauner , Norbert Klempier The synthesis of 5-hydroxymethyl-, 5-acetoxymethyl-, 5-formyl- and 5-cyanothieno[2,3-d]pyrimidines, the (methyl)-5-carboxylate, and the respective amide functionality was accomplished by building up the functionalized molecule starting from appropriately substituted thiophene precursors. A similar strategy starting from the pyrimidine precursor and subsequent direct functionalization (formylation and cyanation) of the thieno[2,3-d]pyrimidine parent compound in position 5 was found to be less feasible. Graphical abstract image
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BF3·OEt2-mediated alkenylation of pyrroles with α-oxo ketene dithioacetals ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Xiaoge Yang , Kaikai Wu , Zhengkun Yu BF3·OEt2-mediated alkenylation of pyrroles with α-oxo ketene dithioacetals was efficiently realized, affording mono- and disubstituted ketene pyrrolyl acetals. In the cases of using N-unprotected pyrrole, the reactions gave ketene bipyrrolyl acetals as well as N,O-chelated BF2 complexes. Diverse C–S transformations were achieved for the monosubstituted products, yielding N-heterocycles or multisubstituted olefins. Graphical abstract image
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Metal-free chemoselective oxidation of sulfides to sulfoxides catalyzed by immobilized taurine and homotaurine in aqueous phase at room temperature ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Hai-Min Shen , Wen-Jie Zhou , Hong-Ke Wu , Wu-Bin Yu , Ning Ai , Hong-Bing Ji , Hong-Xin Shi , Yuan-Bin She Natural products taurine and homotaurine were immobilized on the hybrid silica successfully and characterized by FT-IR, XPS, contact angle measurement, SEM, TGA, and XRD systematically. When the immobilized taurine (Tau@Si) and homotaurine (HTau@Si) were employed as heterogeneous catalysts in the oxidation of aromatic sulfides and aliphatic sulfides with 30% H2O2 at room temperature, up to 99.9% conversion and 98.0% selectivity were achieved with an excellent substrate tolerance. And the heterogeneous catalysts can be easily recycled up to 6times without significant decrease in catalytic activity, which makes them promising catalysts for practical and large-scale applications in the oxidation of sulfides in aqueous phase at room temperature. Graphical abstract image
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The intramolecular Diels–Alder vinylfuran (IMDAV) reaction: a short approach to aza-analogues of pinguisane-type sesquiterpenes ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Yuriy I. Horak , Roman Z. Lytvyn , Yuriy V. Homza , Vladimir P. Zaytsev , Dmitriy F. Mertsalov , Maria N. Babkina , Eugenia V. Nikitina , Tadeusz Lis , Vasyl Kinzhybalo , Vasyl S. Matiychuk , Fedor I. Zubkov , Alexey V. Varlamov , Mykola D. Obushak The reaction of readily accessible (3-furyl)allylamines with maleic anhydride, followed by a domino sequence involving acylation/cycloaddition/proton shift steps, led to the formation of furo[2,3-f]isoindoles—the aza-analogs of pinguisane-type sesquiterpenes. The key intramolecular Diels–Alder vinylfuran (IMDAV) reaction proceeded under mild conditions, with high levels of diastereoselectivity and satisfactory yields. Graphical abstract image
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Agelamadin F and tauroacidin E, bromopyrrole alkaloids from an Okinawan marine sponge Agelas sp. ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Taishi Kusama , Naonobu Tanaka , Yoshiki Kashiwada , Jun’ichi Kobayashi A new structurally unique bromopyrrole alkaloid, agelamadin F (1), comprising oroidin and 3-hydroxypyridinium was isolated from an Okinawan marine sponge Agelas sp. together with tauroacidin E (2), a new bromopyrrole alkaloid possessing a taurine moiety. Six known bromopyrrole alkaloids, oroidin, tauroacidin A, sceptrin, ageliferin, nagelamide E, and agelongine were also isolated and identified. The structures of 1 and 2 were elucidated on the basis of spectroscopic evidences, while chiral HPLC analysis suggested tauroacidin E (2) to be a racemate. Graphical abstract image
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Air–water interface effects on the regioselectivity of singlet oxygenations of a trisubstituted alkene ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Belaid Malek , Ashwini A. Ghogare , Rajib Choudhury , Alexander Greer The regioselective synthesis of allylic hydroperoxide sulfonates by singlet oxygenation at the air–water interface has been found to depend on the concentration of the alkene sulfonate and added calcium salt. The regioselectivity is proposed to originate from an orthogonal alkene relative to the water surface for preferential methyl hydrogen abstraction by airborne singlet oxygen in an ene reaction. The findings hint that the air–water interface is a locale for synthetic reactions. Graphical abstract image
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Concise synthesis of the DEFG ring system in rubriflordilactone B ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Yu Peng , Shu-Ming Duan , Ya-Wen Wang The first synthesis of 6,5,5,5-tetracyclic moiety related with promising anti-HIV activity in rubriflordilactone B has been efficiently achieved. Our strategy started from cheap materials, and features the utilization of radical 1,5-H abstraction/cyclization and vinylogous Mukaiyama aldol reaction, which successfully established the array of five continuous stereogenic carbon centers in the target. Graphical abstract image
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Synthesis of a C2-aryl-pyrrolo[2,1-c][1,4]benzodiazepine monomer enabling the convergent construction of symmetrical and non-symmetrical dimeric analogs ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Robert V. Kolakowski , Thomas D. Young , Philip W. Howard , Scott C. Jeffrey , Peter D. Senter We disclose the synthesis of a versatile C2-aryl-pyrrolo[2,1-c][1,4]benzodiazepine (PBD) monomer that enables the late-stage diversification and synthesis of PBD dimers. The monomer unit was elaborated and dimerized utilizing different tethers to yield symmetric and non-symmetrical C2-aryl-PBD dimers. The dimers were tested for cytotoxic activity on a number of cancer cell lines and showed potent cytotoxicity in the nanomolar to picomolar range. The synthesis of PBD monomers enables the modular construction of PBD free drugs and drug-linkers that may have application for the development of antibody–drug conjugations. Graphical abstract image
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Non-enzymatic transformation of dl-glyceraldehyde, 1,3-dihydroxyacetone, and pyruvaldehyde with primary amine to the same dl-alanine derivatives ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Yande Huang , Charles Pathirana , Qingmei Ye , Venkatapuram Palaniswamy The condensation of a chiral primary alkyl amine, (1S,2S)-2-amino-1-(4-nitrophenyl)propane-1,3-diol (1) as a model compound with dl-glyceraldehyde dimer (2), 1,3-dihydroxyacetone dimer (3), and pyruvaldehyde (4), respectively, forms the same diastereomeric dl-alanine derivatives (6 and 7) as major products. A plausible mechanism is proposed to elaborate such non-enzymatic transformation. Graphical abstract image
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Photo-[4+4]-cycloaddition (para) of meta-substituted benzenes with 2-pyridones ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Buddha B. Khatri , Darius Vrubliauskas , Scott McN. Sieburth Benzene is unreactive as a photochemistry partner with 2-pyridone, however benzene substitution can allow for an efficient [4+4] (a k a, ‘para’) photocycloaddition. Productive substituents include alkoxy, cyano, ester, and trifluoromethyl, suggesting that inductively electron-withdrawing groups are sufficient, however a single fluorine substituent does not result in cycloaddition. When the product of this cycloaddition contains a conjugated system (e.g., an unsaturated ester) a secondary photocycloaddition can follow, forming triply bridged all-syn-[3]ladderane products. Graphical abstract image
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Oxone-promoted hydration of electron-deficient allenic esters and ketones into 1,3-dicarbonyl compounds ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Yu-Ping Yi , Yan Zheng , Jing Nie , Jun-An Ma A novel and mild protocol for the hydration of electron-deficient allenic esters and ketones into various 1,3-dicarbonyl compounds is described. The hydration of allenes promoted by oxone in DMF afforded the corresponding products in moderate to good yields. This work features the employment of only a catalytic amount of inexpensive and nontoxic solid reagent oxone (2KHSO5·KHSO4·K2SO4), avoiding the utility of toxic metals or traditional Brønsted acids, in a green version of viewpoint. A possible reaction mechanism for this transformation is also primarily proposed. Graphical abstract image
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Microwave-promoted direct amidation of unactivated esters catalyzed by heteropolyanion-based ionic liquids under solvent-free conditions ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Renzhong Fu , Yang Yang , Yunsheng Ma , Fei Yang , Jingjing Li , Wen Chai , Quan Wang , Rongxin Yuan A simple and efficient procedure for the synthesis of amides directly from unactivated esters and amines catalyzed by heteropolyanion-based ionic liquids under microwave-promoted and solvent-free conditions has been reported. The practical protocol was found to be compatible with different structurally diverse substrates. Moderate to excellent yields, solvent-free media, and operational simplicity are the main highlights. Furthermore, the heteropolyanion-based ionic liquids were easily reusable for this amidation. Graphical abstract image
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The use of dialkyl acetals in the N-alkylation of 8-oxoadenosine and guanosine. Mechanistic studies and rate determination ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Tewoderos Ayele , Stephanie J. Chang , Marino J.E. Resendiz The use of seven N,N-dimethylformamide dialkyl acetals (methyl-, ethyl-, benzyl-, n-propyl-, n-butyl-, t-butyl, and neopentyl-) was explored for the exocyclic amine protection and subsequent N-alkylation of 8-oxoadenosine and guanosine. Reactions occurred in good to modest yields (50–95%) upon addition of heat (60°C) using DMF as solvent. We determined relative rates of reaction and kinetic experiments resulted in the following order: Me≫Bn≈ t-Bu≫Et≈ n-Pr≈ n-Bu>Me (Np, neopentyl). We found that groups that stabilize a pseudo-carbocation intermediate facilitate the completion of the reaction and lead to different reaction pathways, including elimination of isobutylene and ethylene in some cases. Graphical abstract image
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Single step synthesis of an ethynylferrocenyl-[4]-ferrocenophane ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Anna Serra-Muns , Peter Mayer , Dany Capitao , Claire Fave , Bernd Schöllhorn A single step preparation of a novel [4]-ferrocenophane containing an ethynyl-ferrocene directly connected to the unsaturated heteroannular bridge starting from 1,1′-diformyl-ferrocene is reported. The suggested mechanism involves the reaction of water with the unstable diethynyl-ferrocene intermediate. The crystallographic structure of this multi-functional molecule has been resolved. Graphical abstract image
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An efficient scale up process for synthesis of N-arylpiperazines ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Lokesh Ravilla , N. Venkata Subba Naidu , Kuppuswamy Nagarajan An efficient protocol for the synthesis of various substituted phenylpiperazines was developed using sulfolane as solvent. The protocol was clean, high yielding and products were obtained in high purities (⩾99%). It was also fast and convenient, as the final products were precipitated as hydrochloride salts and could be obtained by filtration. Sulfolane, an aprotic, dipolar, high boiling and recoverable solvent was used as a substitute for common organic solvents. Graphical abstract image
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Thermo-triggered release of a Cys probe from the cavity of a water-soluble pillar[5]arene ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Xiaodong Chi , Pi Wang , Yang Li , Xiaofan Ji A novel [2]pseudorotaxane based on thermo-responsive water-soluble pillar[5]arene WP5 and Cys probe 1 was successfully prepared in water. This complex exhibited no responsiveness to Cys at room temperature due to its high stability that inhibited the interaction between probe 1 and Cys. However, the encapsulated 1 could be released from the cavity of WP5 upon heating, leading to the formation of 1–Cys adduct. Moreover, the probe could be used to monitor Cys with high sensitivity. Importantly, WP5, 1, and the [2]pseudorotaxane WP5⊃1 showed excellent biocompatibility, making the probe a very attractive candidate for biological applications. Graphical abstract image
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Synthesis of various lignans via the rearrangements of 1,4-diarylbutane-1,4-diols ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Samuel J. Davidson , David Barker Selectively functionalised 1,4-diarylbutane-1,4-diols have been shown to undergo a number of different reactions upon treatment with methanesulfonyl chloride and triethylamine. These led to three different sub-classes of lignans, depending on the nature of the aryl groups. Rearrangement leading to the corresponding 4,4-diarylbutanals is the most common transformation and these butanals can be reduced to give analogues of seco-lignans. Graphical abstract image
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Addition of selenium(II) bromide to arylalkynylamides—a route to hypervalent T-shaped 10-Se-3 systems ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Edgars Paegle , Sergey Belyakov , Gilbert Kirsch , Pavel Arsenyan A route for the generation of hypervalent T-shaped 10-Se-3 systems is described involving an interaction between in situ prepared selenium(II) bromide and an aryl alkynyl amide derivative. The existence of hypervalent selenium in both the solid and solution states has been supported by X-ray analysis and 77Se NMR data. Graphical abstract image
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Corrigendum to “Diphenylprolinol silyl ether-derived thioureas as highly efficient catalysts for the asymmetric Michael addition of aldehydes to nitroalkenes” [Tetrahedron Lett. 56/26 (2015) 4036–4038] ()
Publication date: 22 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 30 Author(s): Chunyan He , Xiaochen Ren , Yingle Feng , Yonghai Chai , Shengyong Zhang , Weiping Chen
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Editorial board ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29
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Graphical Contents List ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29
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Metal-catalyzed organic reactions using mechanochemistry ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): José G. Hernández , Tomislav Friščić The past decade has witnessed an explosive growth of interest in mechanochemical reactions by milling or grinding, and rapid expansion of mechanochemical methodologies into different areas of chemistry, from supramolecular chemistry and organic synthesis to metal–organic frameworks and nanoparticle synthesis. This Digest Letter highlights the recent advances in metal-catalyzed mechanochemical reactions, one of the most rapidly developing areas of modern organic mechanosynthesis. Graphical abstract image
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Hemithioindigo—an emerging photoswitch ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Sandra Wiedbrauk , Henry Dube Hemithioindigo (HTI) is an emerging photoswitch with many advantageous properties compared to the commonly used photoswitches like azobenzenes, spiropyranes, or dithienylethenes. In this DIGEST the syntheses, physical and photophysical properties of HTI photoswitches and mechanistic explanations for the latter are reviewed. Emphasis will be placed on those distinct properties that render HTIs into unique phototools. Additionally, a broad variety of applications ranging from supramolecular to biological chemistry is presented to highlight the great potential of HTIs as upcoming, alternative photoswitches. Graphical abstract image
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Sodium sulfide in methanol: a two-in-one reagent for deprotection of silyl and formation of propargyl sulfide ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Ishita Hatial , Raja Mukherjee , Kalyan Senapati , Amit Basak A new reagent Na2S/MeOH for silyl deprotection has been developed. The reagent has several advantages which include deprotection of C-TMS, O-TMS, O-TBS, and O-TBDPS, selective removal of C-TMS and O-TMS in the presence of O-TBS and simultaneous desilylation and sulfide formation in one pot. Graphical abstract image
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Practical and stereoselective synthesis of [6,6,5]-tricyclic core (C1–C13) of eribulin mesylate ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Akondi Srirama Murthy , Srivari Chandrasekhar Fully functionalised [6,6,5]-tricyclic core (C1–C13) of eribulin is stereoselectively synthesized from d-mannose. This simple and practical approach involves Still and Gennari modification of HWE-reaction, Sharpless asymmetric dihydroxylation, and oxa-Micheal addition as key reactions. Graphical abstract image
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A practical synthesis of C14–C26 fragment of anticancer drug, eribulin mesylate ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Nadella Lavanya , Nayani Kiranmai , Prathama S. Mainkar , Srivari Chandrasekhar High yielding synthesis of C14–C26 fragment of eribulin is achieved from commercially available R-(+)-citronellol and 1,4-butane diol utilizing the chirality of citronellol ‘methyl’ centre as C25, organocatalytic epoxidation to install C23 chirality and Sharpless asymmetric dihydroxylation to install chirality at C20 and C17. Graphical abstract image
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Tandem organocatalytic approach to C28–C35 fragment of eribulin mesylate ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Lahu N. Chavan , Rambabu Chegondi , Srivari Chandrasekhar The organocatalytic approach is devised for the synthesis of C28–C35 fragment of anticancer drug eribulin mesylate (Halaven®) amenable for scaleup toward total synthesis. Graphical abstract image
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Direct C–N bond cleavage of N-vinyl or N-allyl arylamines: a metal-free strategy for N-devinylation and N-deallylation ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Shilpi Balgotra , Vunnam Venkateswarlu , Ram A. Vishwakarma , Sanghapal D. Sawant A simple and convenient N-devinylation and N-deallylation strategy for N-vinyl and N-allyl arylamines in the presence of TFA/oxone is presented with the formation of selective ortho-hydroxylated and N-trifluoroacylated arylamine product in good yields. This method is important for protection/deprotection of arylamines in organic synthesis and useful as a medicinal chemistry tool at late stage modifications in drug discovery programs. Graphical abstract image
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A phenothiazine–rhodamine ratiometric fluorescent probe for Hg2+ based on FRET and ICT ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Wenqi Zhao , Xingliang Liu , Haitang Lv , Hua Fu , Yan Yang , Ziping Huang , Aixia Han Rhodamine B and phenothiazine building blocks have been used to synthesize a novel ratiometric fluorescent probe 1 for Hg2+. Based on fluorescence resonance energy transfer (FRET) and internal charge transfer (ICT) mechanisms, a low detection limit for Hg2+ of 1.8ppb has been achieved. The intensity ratio (F580nm/F520nm) of fluorescent probe 1 increased on going from 0.1 to 1.0equiv of Hg2+. In the FRET process, energy is transferred from the phenothiazine moiety to the rhodamine B moiety. Probe 1 shows a selective response to Hg2+ by color and fluorescence changes. Graphical abstract image
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Diastereoselective synthesis of the C29–C41 fragment of karlotoxin 2 ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): D. Srinivas Reddy , Janardhan Gaddam , Nagaraju Devunuri , Debendra K. Mohapatra A highly diastereoselective synthesis of the C29–C41 fragment of karlotoxin 2 (KmTx2) is described by employing regio-selective epoxide opening, our own developed domino isomerization followed by C–O and C–C bond formation reaction and chelation-controlled Grignard reaction as key steps. The synthesis involves installation of seven stereocenters present in the C29–C41 fragment of karlotoxin 2. Graphical abstract image
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Solid phase synthesis of ω-aspartic thioacid containing peptides ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Ryan Joseph , Moises Morales Padilla , Philip Garner The Fmoc-based solid phase synthesis of unprotected ω-aspartic thioacid containing peptides is demonstrated. The method involves the novel use of a silyl ester as a carboxylate surrogate for mild peptide bond formation in the presence of a reactive ω-aspartyl thioester. The resulting peptide thioacids may be used in N-glycoligation and other thioacid-mediated conjugation reactions. Graphical abstract image
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α-Arylchalcogenation of acetone with diaryl dichalcogenide via metal-free oxidative C(sp3)–H bond functionalization ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Guobing Yan , Arun Jyoti Borah , Lianggui Wang , Zhangjin Pan , Shuangshuang Chen , Xuqian Shen , Xiangmei Wu Direct α-arylchalcogenation of acetone with diaryl dichalcogenides has been achieved by using a mixture of TBHP and DTBP oxidants at 120°C without transition-metal catalyst via oxidative C(sp3)–H bond functionalization. The method exhibits good functional group tolerance and products were isolated in moderate to high yields. Graphical abstract image
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Transamidation of thioacetamide catalyzed by SbCl3 ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Andrea Ojeda-Porras , Diego Gamba-Sánchez A transamidation reaction of thioacetamide with primary and secondary amines is described. The use of catalytic amounts of SbCl3 notably increases the yields and diminishes the reaction times. Typically, the amines should be aliphatic, but aromatic amines can be used as well, though with lower yields. This is one of the few examples where antimony has been used as a catalyst in organic reactions. Graphical abstract image
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An efficient synthesis of cycloalkane-1,3-dione-2-spirocyclopropanes from 1,3-cycloalkanediones using (1-aryl-2-bromoethyl)-dimethylsulfonium bromides: application to a one-pot synthesis of tetrahydroindol-4(5H)-one ()
Publication date: 15 July 2015 Source:Tetrahedron Letters, Volume 56, Issue 29 Author(s): Hisanori Nambu , Masahiro Fukumoto , Wataru Hirota , Naoki Ono , Takayuki Yakura An efficient synthesis of cyclohexane- and cyclopentane-1,3-dione-2-spirocyclopropanes from 1,3-cycloalkanediones using sulfonium salts was achieved. The reaction of 1,3-cycloalkanediones with (1-aryl-2-bromoethyl)-dimethylsulfonium bromides and powdered K2CO3 in EtOAc provided the corresponding spirocyclopropanes in high yields. Furthermore, a one-pot synthesis of tetrahydroindol-4(5H)-one from 1,3-cyclohexanedione was achieved using the present protocol and a sequential ring-opening cyclization of spirocyclopropane with a primary amine. Graphical abstract image
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