Tetrahedron

Editorial board ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28
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Ten years advancement in the synthetic applications of 2-bromo-cyclohexenecarbaldehydes and 2-bromobenzaldehydes and derived substrates under palladium-catalyzed cross-coupling conditions ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Munmun Ghosh, Jayanta K. Ray 2-bromo-cyclohexenecarbaldehyde and 2-bromobenzaldehyde have long been used as an important tool for the construction loads of compounds of potential biological, medicinal as well as material applications. This review highlights past ten years advancement in the progressive field of bromovinyl aldehyde chemistry focusing on the methods utilizing these substrates under palladium-catalyzed conditions. Graphical abstract image
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Synthesis and NMR spectroscopic conformational analysis of benzoic acid esters of mono- and 1,4-dihydroxycyclohexane, 4-hydroxycyclohexanone and the -ene analogue – The more polar the molecule the more stable the axial conformer ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Erich Kleinpeter, Peter Werner, Torsten Linker para-Substituted benzoic acid esters of cyclohexanol, 1,4-dihydroxycyclohexane, 4-hydroxy-cyclohexanone and of the corresponding exo-methylene derivative were synthesized and the conformational equilibria of the cyclohexane skeleton studied by low temperature 1H and 13C NMR spectroscopy. The geometry optimized structures of the axial/equatorial chair conformers were computed at the DFT level of theory. Only one preferred conformation of the ester group was obtained for both the axial and the equatorial conformer, respectively. The content of the axial conformer increases with growing polarity of the 6-membered ring moiety; hereby, in addition, the effect of sp2 hybridization/polarity of C(4)=O/C(4)=CH2 on the present conformational equilibria is critically evaluated. Another dynamic process could be studied, for the first time in this kind of compounds. Graphical abstract image
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C-Glycosyl 1,2,4-triazoles: Synthesis of the 3-β-d-glucopyranosyl-1,5-disubstituted and 5-β-d-glucopyranosyl-1,3-disubstituted variants ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Katalin E. Szabó, András Páhi, László Somsák Highly variable synthetic routes were elaborated toward trisubstituted C-glycopyranosyl 1,2,4-triazoles. N-Acyl-thioamide derivatives were obtained by acylation of O-perbenzoylated 2,6-anhydro-d-glycero-d-gulo-heptonothioamide by acid chlorides and of thioamides by O-perbenzoylated 2,6-anhydro-d-glycero-d-gulo-heptonoyl chloride. These precursors reacted with substituted hydrazines in a regioselective manner to yield 3-β-d-glucopyranosyl-1,5-disubstituted- and 5-β-d-glucopyranosyl-1,3-disubstituted-1,2,4-triazoles, respectively. Analogous N-acyl-2,6-anhydro-heptonamides failed to give the above triazoles with hydrazines. O-Deprotection of the C-glucosyl 1,2,4-triazoles by the Zemplén method furnished test compounds which showed no inhibition against rabbit muscle glycogen phosphorylase b. Graphical abstract image
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Chirality of the trisubstituted nitrogen center – XRD, dynamic NMR, and DFT investigation of 1,2-dihydrobenzo[e][1,2,4]triazine derivatives ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Piotr Kaszyński, Arkadiusz Kłys, Sławomir Domagała, Krzysztof Woźniak Molecular structures of two 1-aryl-2-benzyloxycarbonyl-1,2-dihydrobenzo[e][1,2,4]triazines 1 were established by single crystal XRD and compared to those of 4-benzyloxycarbonyl (2) and 4-benzyl (4) analogues. The structures revealed a highly pyramidalized asymmetric N(1) center stabilized by steric interactions in 1, but not in 2 and 3. Activation parameters for enantiomer interconversion were obtained by DNMR methods in C6D5Cl: ΔH‡ = 18.1(1) kcal mol−1, ΔS‡ = −0.6(1) cal mol−1 K−1 for Ar = Ph (1a) and ΔH‡ = 18.6(4) kcal mol−1, ΔS‡ = 5.2(6) cal mol−1 K−1 for Ar = 2-anisyl (1b). DFT computational investigation of the origin of the interconversion barrier on model compounds revealed steric destabilization of the inversion TS. Graphical abstract image
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Understanding the optical effects of substituting on the 1,8 and 1,5 positions of corannulene ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Praveen Bachawala, Timothy Ratterman, Necati Kaval, James Mack Corannulene's outer rim was regio-selectively functionalized with ethynyl units at both 1,8 and 1,5-positions and later coupled with phenyl and anthracenyl moieties to study the extent of conjugation through the aromatic framework of corannulene via absorption/emission spectra. Experimental observations were compared with TD-DFT calculations at the level of CAMB3LYP/6-31G* and B3LYP/6-31G*. Laser excitation experiments reveal blue emission for 1,8-bis(phenylethynyl)corannulene and 1,5-bis(phenylethynyl)corannulene which quickly transforms into intense blueish-green in the case of 1,8-bis(9-anthranyl)corannulene and 1,5-bis(9-anthranyl)corannulene. Graphical abstract image
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Synthesis of desmosine-containing cyclic peptide for the possible elucidation of elastin crosslinking structure ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Keita Ogawa, Takahiro Hayashi, Yong Y. Lin, Toyonobu Usuki Elastin is a vital extracellular matrix protein, which is known for providing elasticity in numerous tissues. It is formed by the self-assembly and subsequent crosslinking of elastin precursor, tropoelastin. Two tetrafunctional, pyridinium-based amino acids desmosine and isodesmosine are exclusively found in elastin and play an important role as crosslinkers. Structural elucidation of elastin has eluded scientists to date, owing to the highly cross-linked structure and insoluble nature. Therefore, in this study, we aimed to synthesize a desmosine-containing cyclic peptide as a partial elastin mimic, in order to eventually facilitate the elucidation of the crosslinking pattern of elastin by mass spectrometric analysis. Graphical abstract image
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Synthesis of 2-deoxy ribose related disaccharide nucleoside and its phosphoramidite ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Yili Ding, Rilie Deng, Bingyun Wang Synthesis of impurity reference compound of anti-tumor drug ISIS 183750 was achieved. In this process, a general method for synthesis of 2-deoxy ribosyl disaccharide nucleosides was established for the first time. Graphical abstract image
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Synthesis of trifluoromethylthiolated and trifluoromethylselenolated pyrones ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Yunxiao Zhang, Ding-Yah Yang, Zhiqiang Weng Trifluoromethylthiolation and trifluoromethylselenolation of 3- or 4-iodo(bromo)-2-pyrones with (bpy)CuSCF3 and [(bpy)CuSeCF3]2 provide a convenient method for the synthesis of trifluoromethylthio(seleno)lated 4-alkoxy-, aryloxy-, and benzyloxy-2-pyrones in high yields. Graphical abstract image
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An efficient protocol for the synthesis of six-membered N, O-heterocycles via a 1,3-dipolar (3+3) cycloaddition between nitrile oxide and α-diazo esters ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Bharath Kumar Kuruba, Samuel Vasanthkumar In this manuscript, we are reporting an efficient protocol for the construction of highly functionalized N, O-heterocyclic derivatives such as 1,2,4-oxadiazine and 1,4,2-dioxazine-6-carboxylate derivatives via a 1,3-dipolar (3 + 3) cycloaddition between nitrile oxide and unprotected α-diazo esters in the presence of 2 mol% Cu(OTf)2 catalyst. The expected N, O-heterocycles were obtained in excellent yields. These N, O-heterocycles are known to exhibit insecticidal and acaricidal properties. Graphical abstract image
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Synthesis of a novel tripeptidomimetic scaffold and biological evaluation for CXC chemokine receptor 4 (CXCR4) antagonism ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Markus Baumann, Lina Marie Nome, Zack G. Zachariassen, Stefanie Karlshøj, Torgils Fossen, Mette M. Rosenkilde, Jon Våbenø, Bengt Erik Haug We here report the preparation of a new 2,6,8-trisubstituted bicyclic tripeptidomimetic scaffold through TFA-mediated cyclization of a linear precursor containing three side chains. The introduction of a triphenylmethyl-protected thiol into carboxylic acid containing building blocks through sulfa Michael additions onto α,β-unsaturated hexafluoroisopropyl esters is described. The stereoselectivity of the bicycle formation was found to be somewhat lower than that previously reported for analogous 3,6,8-trisubstituted scaffolds. Moreover, the configuration of the linear precursor directs the stereochemical outcome of the cyclization differently when the R1 side chain is positioned on C2 in the bicycles (present work) instead of C3 (previous work). Tripeptidomimetic compounds based on the new scaffold were synthesized and evaluated for antagonistic potency toward CXCR4, and one compound (45a) displayed similar activity to earlier reported 3,6,8-tripeptidomimetic bicycles. Graphical abstract image
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Synthesis of 4-hydroxyquinoline-2,3-dicarboxylates using N-(2-aminobenzoyl)benzotriazoles ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): İlhami Çelik, Fatoş Yıldız A method for the preparation of 4-hydroxyquinoline-2,3-dicarboxylates has been developed by aza-Michael addition reaction of N-(2-aminobenzoyl)benzotriazoles with dimethyl acetylenedicarboxylate. 4-Hydroxyquinoline-2,3-dicarboxylates were obtained in moderate to good yields (53–87%). Graphical abstract image
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Asymmetric synthesis of benzofuryl β-amino alcohols by the transfer hydrogenation of α-functionalized ketones ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Agnieszka Tafelska-Kaczmarek, Marek P. Krzemiński, Marta Ćwiklińska The asymmetric transfer hydrogenation of representative benzofuryl α-sulfonyloxy ketones and N-protected α-amino ketones with an azeotropic mixture of formic acid/triethylamine, catalyzed by RhCl[(R,R)-TsDPEN](C5Me5), afforded the corresponding 1,2-diol monosulfonates and N-substituted β-amino alcohols in high yields and with enantioselectivities up to 99%. Transformation of the reduction products to the chiral benzofuryl β-amino alcohols possessing a primary amine group is also described. Graphical abstract image
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Water as a hydrogen source in palladium-catalyzed reduction and reductive amination of nitroarenes mediated by diboronic acid ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Yanmei Zhou, Haifeng Zhou, Sensheng Liu, Danwei Pi, Guanshuo Shen An unprecedented palladium-catalyzed chemoselective reduction and reductive amination of nitroarenes with water as a hydrogen source mediated by diboronic acid have been discovered. A series of aryl amines containing various reducible functional groups were obtained in good to excellent yields. Graphical abstract image
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Chemical constituents isolated from Antarctic marine-derived Aspergillus sp. SF-5976 and their anti-inflammatory effects in LPS-stimulated RAW 264.7 and BV2 cells ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Jaeyoung Kwon, Hyaemin Lee, Wonmin Ko, Dong-Cheol Kim, Kwan-Woo Kim, Hak Cheol Kwon, Yuanqiang Guo, Jae Hak Sohn, Joung Han Yim, Youn-Chul Kim, Hyuncheol Oh, Dongho Lee Three new benzaldehydes (1–3) and two new dioxopiperazine alkaloids (4 and 5), along with 23 known constituents, were isolated from Antarctic marine-derived Aspergillus sp. SF-5976. Their structures were determined by spectroscopic and chemical methods. Among them, 20 compounds showed inhibitory effects toward lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages with IC50 values of 7.3–77.4 μM, while 22 compounds did in BV2 microglia with those of 4.6–72.3 μM. Furthermore, the effects of the newly isolated compounds on LPS-stimulated inducible NO synthase (iNOS) expression were investigated, and 1–3, and 5 inhibited iNOS in RAW 264.7 cells, while 1–5 did in BV2 cells. Also, 1–3 and 5 inhibited LPS-induced prostaglandin E2 production with IC50 values of 9.1–66.8 μM in RAW 264.7 macrophages by suppressing cyclooxygenase-2 (COX-2), while in BV2 microglia, 1–5 showed activities with those of 2.8–49.4 μM. Graphical abstract image
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Hydrated ferric sulfate-catalyzed reactions of indole with aldehydes, ketones, cyclic ketones, and chromanones: Synthesis of bisindoles and trisindoles ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Wayland E. Noland, Honnaiah Vijay Kumar, Grant C. Flick, Cole L. Aspros, Jong Hyeon Yoon, Andre C. Wilt, Nasim Dehkordi, Sheng Thao, Andrew K. Schneerer, Siming Gao, Kenneth J. Tritch Hydrated ferric sulfate [Fe2(SO4)3·xH2O] has been found to be an efficient catalyst for condensation of bisindoles or trisindoles with aliphatic or aryl aldehydes and ketones including methyl and ethyl-alkyl ketones, methyl aryl ketones, cyclic ketones, and 4-chromanones in 19–96% yields. Trisindoles and 2,2'-alkylidenebisindoles were obtained from indole-3-carbaldehydes or 3-methylindole in 72–84% yields. A total of 43 substrates was employed, giving 33 bisindoles, 3 trisindoles, and one 2:2 product; seventeen of these are new. The best results were obtained from heating ethanolic suspensions, with Fe2(SO4)3·xH2O loaded at 60 mg per mmol of electrophiles. The reaction times were typically 1–4 h, while hindered electrophiles required 8–24 h. These conditions were strong enough to promote 2:1 condensation of indole with substrates without forming higher-order byproducts, with few exceptions. This strategy features tolerance by the catalyst of a wide range of functional groups, readily available starting materials, simple operation, mild reaction conditions, and is environmentally friendly. Graphical abstract image
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A convenient synthesis of carbohydrate derived furo/pyrano[2,3-b]pyrans from 2-hydroxymethyl glycals ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Sudharani Chalapala, Ramakrishna Bandi, Venkatesh Bhumireddy Chinnachennaiahgari, Ramu Sridhar Perali An efficient method for the stereoselective synthesis of various linearly fused bicyclic acetals using 2-hydroxymethyl glycals, involving Ferrier type rearrangement and ring-closing metathesis as the key steps, is revealed. The methodology was shown to be very general by applying it to various sugar substrates which lead to the formation of various bicyclic furo/pyrano[2,3-b]pyran ring systems. Graphical abstract image
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Rapid assembly of branched mannose oligosaccharides through consecutive regioselective glycosylation: A convergent and efficient strategy ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Bo Meng, Jun Wang, Qianli Wang, Anthony S. Serianni, Qingfeng Pan A convergent and efficient strategy for the synthesis of high-mannose oligosaccharides is described wherein regioselective glycosylations between trichloroacetimidate donors and partially protected acceptors are employed to reduce the number of protection–deprotection steps. Two representative branched mannose oligosaccharides, a mannose heptasaccharide (Man7) and a mannose nonasaccharide (Man9) were constructed via (4 + 3) and (5 + 4) glycosylations, respectively. These mannose-containing oligosaccharides were obtained in nine steps in ∼25% overall yield and >98% purity on 60–70 mg scales to demonstrate the effectiveness of the strategy. Graphical abstract image
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Brønsted acid mediated cyclizations of ortho-aryl(ethynyl)pyrimidines ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Aleksandr N. Shestakov, Alena S. Pankova, Pavel Golubev, Alexander F. Khlebnikov, Mikhail A. Kuznetsov A high-yielding procedure for the synthesis of 5-aryl-4-(arylethynyl)pyrimidines from easily available 2-aryl-3-hydroxyacrylates is reported. These pyrimidines readily undergo cyclization in strong Brønsted acids and, depending on the substitution in alkynylpyrimidines and the water content of the reaction mixture, yield either benzo[f]quinazolines or derivatives of spiro[cyclohexa-2,5-diene-1,5′-cyclopenta[d]pyrimidin]-4-one. In most cases the cyclization proceeds nearly quantitatively. DFT calculations support the proposed mechanisms induced by the protonation of the triple bond in 5-aryl-4-(arylethynyl)pyrimidines. Fluorescent properties of the obtained heterocycles are also described. Graphical abstract image
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The reactions of 1,1-diarylallenes with N-acyliminium cations generated from hydroxylactams ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Anna G. Larina, Alexander S. Filatov, Vitalii V. Suslonov, Alexander P. Molchanov, Alexander V. Stepakov The first example of the reactions of 1,1-diarylallenes with N-acyliminium cations is described. 2-Aryl-3-(3-aryl-1H-inden-2-yl)isoindolin-1-ones and 6-methylene-5,5-diaryl-6,6a-dihydroisoindolo[2,1-a]quinolin-11(5H)-ones were prepared by BF3·OEt2-mediated reactions of 1,1-diarylallenes with the N-acyliminium cations generated from 2-aryl-3-hydroxyisoindolin-1-ones. 2-Aryl-3-(3-aryl-1H-inden-2-yl)isoindolin-1-ones underwent an intramolecular cyclization on treatment with methanesulfonic acid with the formation of compounds exhibiting the indeno[2,1-c]isoindolo[2,1-a]quinoline skeleton. Graphical abstract image
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A flow strategy for the rapid, safe and scalable synthesis of N-H 1, 2, 3-triazoles via acetic acid mediated cycloaddition between nitroalkene and NaN3 ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Dong Li, Lei Liu, Yu Tian, Yongjian Ai, Zhike Tang, Hong-bin Sun, Gang Zhang The N-unsubstituted 4-aryl-1H-1,2,3-triazoles were synthesized via the acetic acid promoted cycloaddition between β-nitrostyrenes with sodium azide under transition-metal-free conditions in a continuous flow microreactor. The continuous-flow microreactor provided a safe environment for the dangerous reagents NaN3 and nitroalkene, and offered such a rapid procedure that the triazoles were formed in less than 4 min. In addition, the excess sodium azide was quenched by the by-product HNO2 in the presence of acetic acid. The scale-up experiment proved again that the yield did not drop in the flow reaction. Moreover, the synthesis of N-unsubstituted 1,2,3-triazole was also explored via a one pot reaction with aldehyde, nitromethane and sodium azide, and this reaction was monitored with an “in-tube retention time gradient” (IT-RTG) technology, which may be a novel application of the continuous-flow microreactor. Graphical abstract image
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The application of Morita-Baylis-Hillman reaction: Synthetic studies on perophoramidine ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Lin Wu, Qian-Ru Zhang, Ji-Rong Huang, Yang Li, Fu Su, Lin Dong A new concise methodology was developed for the synthesis of the two vicinal quaternary centers of the natural product perophoramidine. Key steps involved the Morita–Baylis–Hillman reaction, reductive cyclization and allylic alkylation. Moreover, most conditions are simple and convenient with good yields. Graphical abstract image
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Design and properties of glutamic acid-based coumarin derivatives as organogelators ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Daisuke Yakeya, Naoya Kitou, Shougo Kinugawa, Tetsuji Moriguchi, Akihiko Tsuge Two kinds of glutamaic acid-based coumarin derivatives show a quite different trend against gelation in organic solvents in terms of inter- or intramolecular hydrogen bonds involved. It has been found out that addition of the valinate structure into the coumarine derivative could improve its gelation ability. Graphical abstract image
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Microwave assisted solvent- and catalyst-free three-component synthesis of NH-1,2,3-triazoloimines ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Alevtina S. Medvedeva, Maria M. Demina, Tatyana V. Kon'kova, Thi Le Huyen Nguyen, Andrei V. Afonin, Igor A. Ushakov Highly efficient microwave-assisted solvent- and catalyst-free multicomponent synthesis of 5-R-imino-[4-trialkylsilyl(germyl)]-1H-1,2,3-triazoles from Si/Ge-substituted propynals, trimethylsilyl azide and functionalized primary amines has been developed. In the case of 2-aminoethanethiol, 4-element substituted 5-(1,3-thiazolan-2-yl)-1H-1,2,3-triazoles have been obtained. Their heterolysis by MeOH at room temperature leads to the corresponding triazoloimines in high yield. Graphical abstract image
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Synthesis of 2H-benzimidazole 1,3-dioxides, separase inhibitors, by reaction of o-benzoquinone dioximes with ketones ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Elena Chugunova, Vladimir Samsonov, Nurgali Akylbekov, Dmitrii Mazhukin The synthesis of novel 2H-benzimidazole 1,3-dioxides on the basis of o-benzoquinone dioximes interaction with ketones in the presence of acids is described. Nitration of these compounds by nitric acid in acetic acid yields the 5-nitro derivatives of 2H-benzimidazole 1,3-dioxide. Graphical abstract image
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A chemiluminescence sensor with signal amplification based on a self-immolative reaction for the detection of fluoride ion at low concentrations ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Shugo Hisamatsu, Shinichi Suzuki, Shigeo Kohmoto, Keiki Kishikawa, Yusuke Yamamoto, Ryuhei Motokawa, Tsuyoshi Yaita A sensory system incorporated with an amplification function was developed for the detection of trace-level fluoride ions. This sensory system comprises two steps: amplification and chemiluminescence. These steps were linked with chemical reactions and were induced continuously. The process from amplification to chemiluminescence was accomplished in this system using fluoride ions. The amplification is based on a self-immolative system that permits the detection of emissions even at low fluoride ion concentrations for systems in which chemiluminescence cannot be induced in the absence of fluoride ions. The optimal ratio of the chemiluminescent compound and the amplifier was calculated to achieve efficient amplification. Graphical abstract image
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Copper-catalyzed reductive borylations on water ()
Publication date: 6 July 2017 Source:Tetrahedron, Volume 73, Issues 27–28 Author(s): Chihiro Tanaka, Kimiaki Nakamura, Takashi Nishikata In this paper, we established copper catalyzed reductive borylation of terminal alkynes and diboron on water in the presence of amine. Moderate conditions enabled selective borylations of vinyl-substituted phenylacetylenes to undergo the borylation at a CC triple bond. The Cu catalyst can be recycled for seven times. Graphical abstract image
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Editorial board ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26
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Tetrahedron Young Investigator Award ∼ 2017 ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26
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Literature ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26
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Polyketides from the endophytic fungus Phomopsis sp. sh917 by using the one strain/many compounds strategy ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Jian-Wei Tang, Wei-Guang Wang, Ao Li, Bing-Chao Yan, Rong Chen, Xiao-Nian Li, Xue Du, Han-Dong Sun, Jian-Xin Pu On the basis of One Strain/Many Compounds (OSMAC) strategy, five new polyketides, named phomopsiketones A-C (1–3), (10S)-10-O-β-D-4′-methoxymannopyranosyldiaporthin (7), and clearanol H (10), and two new natural products, 4 and 5, along with three known ones, 6, 8 and 9, were isolated from an endophytic fungus, Phomopsis sp. sh917, harbored in stems of Isodon eriocalyx var. laxiflora. Their structures were elucidated by spectroscopic methods. The absolute configurations of 1, 3, and 7 were further confirmed by single crystal X-ray diffraction experiment. Compounds 2, 4, 6, 9 and 10 were assigned absolute configurations on the basis of circular dichroism (CD) or optical rotation (OR) data comparison. In addition, antiangiogenic activity of compounds 2, 3, 5, and 6 were evaluated by using human umbilical vascular endothelial cells (HUVECs) in a cell-culture model of angiogenesis. Especially, compound 6 sufficiently inhibited vascular endothelial growth factor (VEGF)-induced angiogenic processes in vitro, including migration, invasion, and tube formation of HUVECs. Graphical abstract image
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Isolation, structure elucidation and biosynthesis of benzo[b]fluorene nenestatin A from deep-sea derived Micromonospora echinospora SCSIO 04089 ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Xiaodong Jiang, Qingbo Zhang, Yiguang Zhu, Fangling Nie, Zhengchao Wu, Chunfang Yang, Liping Zhang, Xinpeng Tian, Changsheng Zhang Benzofluorene-containing angucyclines, such as lomaiviticins, kinamycins, and fluostatins, have attracted increasing attentions on chemical synthesis and biosynthesis due to their unique structures and potent biological activities. Our continuous searching for novel natural products from deep-sea derived actinomycetes led to the discovery of nenestatin A (1), a benzo[b]fluorene compound possessing a carbon scaffold similar to the monomeric lomaiviticins, from the deep sea-derived Micromonospora echinospora SCSIO 04089. In addition, the biosynthetic gene cluster of nenestatin A (nes) was identified by a genome sequencing approach and comparative bioinformatics analysis with the lomaiviticin biosynthetic gene clusters. The nes-gene cluster was further verified by in vivo gene disruption experiments to afford a biosynthetic intermediate homo-dehydrorabelomycin E (2). This study adds a new member to the growing family of benzofluorene angucyclines and paves the way for further biosynthetic investigations. Graphical abstract image
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P(NMe2)3-promoted ortho-selective arylation of phenols with diaryliodonium triflates via rhodium catalysis ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Qi-Sheng Liu, De-Yin Wang, Jin-Fei Yang, Zhong-Yi Ma, Mengchun Ye Rh-catalyzed ortho-selective arylation of free phenol with diaryliodonium triflates to widely existed phenol-containing biaryls have been developed. The use of P(NMe2)3, t BuOLi and CH3CN proved to be critical for the ortho-selectivity of this reaction. Graphical abstract image
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Construction of carbocycles initiated by Cu-catalyzed radical reaction of Cl2C(CN)2 ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Keisuke Masuda, Masashi Tanigawa, Masanori Nagatomo, Daisuke Urabe, Masayuki Inoue A Cu-catalyzed radical reaction of Cl2C(CN)2 was utilized for stereoselective conversion of unsaturated molecules into functionalized carbocycles. Chloromalononitrile radicals, generated by treating Cl2C(CN)2 with catalytic amounts of CuCl and dppf in refluxing dioxane, intermolecularly reacted with the unsaturated bonds of acyclic or 10-membered compounds. The resultant carboradicals then intramolecularly added to another unsaturated bond to produce 1,2-disubstituted cyclopentane or trans-decalin derivatives. The chemo- and stereoselectivities of these radical cascade reactions are discussed in detail. Graphical abstract image
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Enantiomerically pure tetraphenylene-based homochiral macrocyclic tetramer and its recognition property towards C76 fullerene ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Chun-Lin Deng, Xiao-Shui Peng, Henry N.C. Wong The synthesis and characterization of novel homochiral oligomacrocycle species composed of enantiomerically-pure tetraphenylene were described. Structural studies showed that the macrocyclic molecule possessed a helical chiral cavity, which exhibited unique and efficient recognition affinity towards fullerene C76 in toluene, as demonstrated by UV–vis titration experiments. The binding results were also interpreted through semi-empirical calculations. Graphical abstract image
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Asymmetric total synthesis of (−)-perforanoid A ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Chao Lv, Qian Tu, Jianxian Gong, Xiaojiang Hao, Zhen Yang Asymmetric total synthesis of (−)-perforanoid A, a novel limonoid isolated from the leaves of Harrisonia perforata, has been achieved. The key features of our total synthesis include the Rh-catalyzed intramolecular Pauson–Khand reaction of an allene and an alkene, the Pd-catalyzed lactonization of an allylic alcohol with a vinyl ether, and the enantioselective alkenylation of 3-furaldehyde. Graphical abstract image
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Oxidative cleavage of hydroxamic acid promoted by sodium periodate ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Changchun Yuan, Biao Du, Miao-Miao Xun, Bo Liu A series of hydroxamic acids, involving aliphatic, aromatic and cyclic substrates, were transformed to the corresponding carboxylic acids through NaIO4-mediated oxidative cleavage in mild conditions. Esterification of these acids with TMSCHN2 could result in formation of the corresponding methyl ester. This methodology makes good compensation for the existing methods transforming amides to esters. Our results also pave the way to harness hydroxamic acids as useful synthetic building blocks. Graphical abstract image
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Synthetic study toward the total synthesis of solanoeclepin A ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Gang Liu, Jing-Chun Han, Chuang-Chuang Li A concise approach for the stereoselective construction of the oxa-pentacyclic core of solanoeclepin A has been developed by using the intramolecular Diels-Alder (IMDA) reaction from the furan-tethered dienophile. Graphical abstract image
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N-alkylation of 2-pyridone derivatives via palladium(II)-catalyzed directed alkene hydroamination ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): John A. Gurak, Van T. Tran, Miranda M. Sroda, Keary M. Engle A selective N-alkylation reaction of 2-pyridones and related heterocycles via intermolecular alkene hydroamination is reported. The reaction utilizes palladium(II) acetate as a catalyst and employs a bidentate directing group to dictate the regioselectivity for both unactivated terminal and internal alkenes. High functional group tolerance is observed across a widerange of electronically diverse 2-pyridones and other aza-heterocycles, including 1-hydroxyisoquinoline, 2-hydroxyquinoline, pyridazinone, pyrimidinone, and pyrazinone. Graphical abstract image
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Scalable synthesis of enaminones utilizing Gold's reagents ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Alexander W. Schuppe, James M. Cabrera, Catherine L.B. McGeoch, Timothy R. Newhouse Several Gold's reagents were synthesized from cyanuric chloride and N,N-dialkylformamides. These synthetic equivalents of N,N-dimethylformamide dimethyl acetal were used in an optimized and scalable procedure for the regioselective synthesis of a variety of enaminones from ketone starting materials, whose utility was demonstrated by the stereoselective synthesis of Rawal-type dienes. Graphical abstract image
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Total synthesis of (+)-methynolide using a Ti-mediated aldol reaction of a lactyl-bearing oxazolidin-2-one, and a vinylogous Mukaiyama aldol reaction ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Takahiro Suzuki, Masataka Fujimura, Kazuhiro Fujita, Susumu Kobayashi A highly convergent total synthesis of (+)-methynolide, based on two types of stereoselective aldol reaction, was achieved. The C1-C8 and C9-C11 fragments of (+)-methynolide were prepared by a vinylogous Mukaiyama aldol reaction using a vinyl ketene silyl N,O-acetal, and a Ti-mediated aldol reaction of a lactyl-bearing chiral oxazolidin-2-one, respectively. Yamaguchi esterification of both fragments and ring-closing metathesis afforded (+)-methynolide. Graphical abstract image
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Iron-catalyzed selective oxidative arylation of phenols and biphenols ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Vlada Vershinin, Alina Dyadyuk, Doron Pappo The single-step synthesis of protected fucols and unnatural polyaryls by biomimetic oxidative cross-coupling between phenolic components and 1,3,5-trimethoxybenzene catalyzed by FeCl3 in fluorinated solvents is reported. The regioselectivity (ortho, meta or para) and the chemoselectivity (CC vs CO) in this highly efficient transformation are controlled by the phenolic ortho-groups of the growing phenolic oligomer. The reaction scope was examined by coupling biphenol derivatives with the nucleophilic arene to afford large polyaryl compounds that are not easily accessible by other means. The versatility of the catalytic system in designing polyaryl frameworks was demonstrated by performing a sequential oxidative phenol-phenol and phenol-arene coupling reaction that afforded a single polyaryl product in high efficiency. Graphical abstract image
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Synthesis of multiply arylated pyridines ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Takashi Asako, Wakana Hayashi, Kazuma Amaike, Shin Suzuki, Kenichiro Itami, Kei Muto, Junichiro Yamaguchi We have achieved a synthesis of multiply arylated pyridines by using a [4 + 2] cycloaddition of 2,4-diaryl-5-chloroxazoles and cinnamic acids as a key reaction. The resulting hydroxytriarylpyridines can be derivatized into triarylpyridines, tetraarylpyridines and pentaarylpyridines by sequential cross-couplings. This synthetic method allows for facile and rapid access to highly arylated pyridines with different aryl substituents. Graphical abstract image
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A facile method to enable a model phospholipid cell-permeable and photoactivatable ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Manish K. Singh, Jarod Waybright, Qisheng Zhang Directly utilizing phospholipids in cellular studies is limited by their dynamic metabolism and lack of cell permeability. We have developed a facile method to enable a fluorescent model phospholipid cell-permeable and photoactivatable. This method features the reaction of a diazo-containing molecule with either phosphonic or phosphoric acids to form the corresponding photocaged esters under mild conditions, and should be generally applicable to endogenous phospholipids. Graphical abstract image
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Asymmetric dearomative spirolactonization of naphthols using λ3-iodanes under chiral phase-transfer catalysis ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Kevin Antien, Guillaume Viault, Laurent Pouységu, Philippe A. Peixoto, Stéphane Quideau The asymmetric phase-transfer catalytic effect of chiral Cinchona alkaloid-derived quaternary ammonium salts was investigated in the context of the λ3-iodane-mediated dearomative spirolactonization of naphthols. The scope and limitations of this methodology were evaluated using various substrates, which were converted into spirolactones in good yields and with enantiomeric excesses up to 58%. Graphical abstract image
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Biomimetic synthesis of myrtucommulone K, N and O ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Liangbo Lv, Yulong Li, Yuhan Zhang, Zhixiang Xie A concise total synthesis of myrtucommulone K, N and O have been developed in 4 steps from commercially available materials. The synthetic strategy was inspired primarily by the biogenetic hypothesis and firstly enabled via a reduction, dehydration sequence for preparing isobutylidenesyncarpic acid followed by a hetero-Diels-Alder reaction to disclose the target moleculars. In this approach the exocyclic double bond of (−)-β-caryophyllene was more active than the endocyclic one in hetero-Diels–Alder reaction as the dienophile. The route is protecting-group-free, concise step, redox and pot economy. Graphical abstract image
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Ketone-catalyzed photochemical C(sp3)–H chlorination ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Lei Han, Ji-Bao Xia, Lin You, Chuo Chen Photoexcited arylketones catalyze the direct chlorination of C(sp3)–H groups by N- chlorosuccinimide. Acetophenone is the most effective catalyst for functionalization of unactivated C–H groups while benzophenone provides better yields for benzylic C–H functionalization. Activation of both acetophenone and benzophenone can be achieved by irradiation with a household compact fluorescent lamp. This light-dependent reaction provides a better control of the reaction as compared to the traditional chlorination methods that proceed through a free radical chain propagation mechanism. Graphical abstract image
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Nucleophilic disulfurating reagents for unsymmetrical disulfides construction via copper-catalyzed oxidative cross coupling ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Zhihong Dai, Xiao Xiao, Xuefeng Jiang Novel disulfuration was established via cross coupling between nucleophilic disulfurating reagent and arylsilane introducing two sulfur atoms in one step. This methodology was applied to synthesize various unsymmetrical disulfides under mild conditions via copper-catalyzed oxidative Hiyama-type cross coupling, providing a new pathway for disulfide synthesis. In addition, pH value of system displayed a key role in alcoholysis process. Graphical abstract image
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Enantioselective synthesis of crotyl geminal bis(silane) and its usage for asymmetric Sakurai allylation of acetals ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Yang Chu, Qiang Pu, Zhixing Tang, Lu Gao, Zhenlei Song Enantioselective synthesis of crotyl geminal bis(silane) 4 has been developed by an asymmetric [1, 5]-hydride shift of allylic hydrazine. SnCl4-promoted Sakurai allylation of (R)-4 with acetals leads to chemoselective desilylation of SiMe3, generating E-syn-(S, R)-5 in good yields with high E/Z-, diastereo- and enantioselectivity. Graphical abstract image
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Structural and mechanistic study of the cysteine oxidation-mediated induction of the Escherichia coli MarR regulator ()
Publication date: 29 June 2017 Source:Tetrahedron, Volume 73, Issue 26 Author(s): Rongfeng Zhu, Ziyang Hao, Hubing Lou, Yanqun Song, Jingyi Zhao, Jiuhe Zhu, Peng R. Chen Multiple antibiotic resistance regulator (MarR) family proteins are widely conserved transcription factors that are important for regulating bacterial resistance to various stresses. Escherichia coli MarR, the prototype member of this family, has recently been shown to undergo interdimer disulfide bond formation via a unique cysteine residue (Cys80) that ultimately triggered MarR's dissociation from its promoter DNA. However, these structural studies were performed with cysteine mutants while the structure of wild type MarR remains uncharacterized. Here we report the crystal structure of wild type MarR in the absence of DNA, which further revealed the roles of cysteine residues in MarR's transcriptional regulation. In addition, we developed a circularly permuted yellow fluorescent protein (cpYFP)-based environmental-sensitive fluorescent reporter for in situ detection of the DNA-binding induced conformational change on MarR, which verified the induction mechanism of this prototypical MarR family protein. This strategy might potentially be applicable for monitoring local conformational change within diverse protein structures. Graphical abstract image
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