Tetrahedron Letters

Editorial board ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40
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Graphical Contents List ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40
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Palladium-catalyzed denitrogenative Hiyama cross-coupling with arylhydrazines under air ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Hui Zhang, Chunjie Wang, Zhiwei Li, Ziyun Wang A Pd-catalyzed denitrogenative Hiyama coupling of arylhydrazines and aryl silanes is described under mild conditions. The newly developed catalytic system does not require the use of expensive silver- or copper-based stoichiometric oxidants to obtain diaryl derivatives with high selectivity and reactivity. The reported coupling reactions are very practical as they do not require the protection of inert gas or oxygen and are tolerant to many functional groups. Graphical abstract image
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Cymoside, a monoterpene indole alkaloid with a hexacyclic fused skeleton from Chimarrhis cymosa ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Christelle Lémus, Marina Kritsanida, Alban Canet, Grégory Genta-Jouve, Sylvie Michel, Brigitte Deguin, Raphaël Grougnet Cymoside, an oxidized derivative of strictosidine with an unprecedented hexacyclic skeleton which includes a double bridge linking the indole and the monoterpene moieties has been isolated from the leaves of Chimarrhis cymosa. The structure of this alkaloid, its relative and absolute configurations have been established by spectroscopic data including 1D and 2D NMR experiments (COSY, HSQC, HMBC, NOESY), HRESIMS and electronic circular dichroïsm (ECD) calculations. Graphical abstract image
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Thermal rearrangement of 2,3-diaryl-1-phthalimidoaziridines ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Alena S. Pankova, Mariia V. Sorokina, Mikhail A. Kuznetsov 2,3-Diaryl-1-phthalimidoaziridines and 2,3-diaryl-1-phthalimidoaziridine-2-carbonitriles were found to readily undergo thermal rearrangement into imines via 1,2-migration of the phthalimido group and accompanying C–C bond cleavage. Isomerization proceeds regioselectively with preferable migration to the electron-deficient carbon atom. Interestingly, this reaction was found to predominate even in the presence of dipolarophiles. Graphical abstract image
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Intermolecular heterocyclization of alkynones with 2-mercaptoacetaldehyde under metal-free conditions: synthesis of 2,3-disubstituted thiophenes ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Erol Can Vatansever, Kübra Kılıç, Merve Sinem Özer, Gani Koza, Nurettin Menges, Metin Balci A concise and regioselective approach for the synthesis of 2,3-disubstituted thiophene derivatives has been developed. The synthetic strategy relies on the reaction of an in situ generated 2-mercaptoacetaldehyde with various alkynones. Furthermore, we calculated the energy gap between the HOMO and the LUMO orbitals of all compounds and observed that the introduction of a strong electron-withdrawing group decreased the HOMO–LUMO energy gap. Graphical abstract image
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Metal-free tandem Beckmann–electrophilic aromatic substitution cascade affording diaryl imines, ketones, amines, and quinazolines ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Samuel R.S. Sarsah, Marlon R. Lutz, Kailyn Chichi Bobb, Daniel P. Becker A cascade reaction sequence involving a Beckmann rearrangement on benzophenone oxime followed by an electrophilic aromatic substitution (EAS) on the intermediate nitrilium ion affords N-phenyl diaryl imines that may then be hydrolyzed to ketones, or reduced to the corresponding amines. Reaction with benzonitrile afforded 2,4-diphenylquinazoline through a Beckmann–Ritter–EAS cascade. Graphical abstract image
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Colorimetric signaling of Cu(II) ions by oxidative coupling of anilines with 4-aminoantipyrine ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Ja Min Hong, Jae Kyeong Jun, Hong Yeong Kim, Sangdoo Ahn, Suk-Kyu Chang Selective Cu2+ signaling by the oxidative coupling of anilines with 4-aminoantipyrine was investigated. The Cu2+-assisted reaction between N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethylaniline sodium salt and 4-aminoantipyrine resulted in the pronounced color change from colorless to bluish green, with a detection limit of 2.1×10−6 M in 90% aqueous acetonitrile. Furthermore, selective Cu2+ signaling was not affected by the presence of common metal ions as background. The practical utility of this system for the determination of Cu2+ was successfully demonstrated using a convenient chromogenic test strip. Graphical abstract image
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A convenient synthesis of phosphonomethyl α,β-unsaturated γ-lactams ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Abderrahmen Abdelli, Mohamed Lotfi Efrit, Anne Gaucher, Hedi M’rabet, Damien Prim A versatile access to diversely substituted α,β-unsaturated γ-lactams is described using a common allylphosphonate precursor. The construction of the γ-lactam motive is based on two steps including a key sequential one-pot Michael addition–Nef sequence that allows the preparation of keto-ester intermediates. Our methodology allowed the selective installation of various alkyl, cycloalkyl and aryl substituents as well as a valuable phosphonomethyl fragment at positions 1 and 3 of the heterocycle. Graphical abstract image
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Facile ligand-free Pd-catalyzed tandem C–C/C–N coupling reaction: a novel access to highly diverse tetrazole tag isoindoline derivatives ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Moni Sharma, Irfan Khan, Shahnawaz Khan, Rohit Mahar, Sanjeev K. Shukla, Ruchir Kant, Prem M.S. Chauhan A novel and robust route for the synthesis of diversely substituted isoindoline skeletons through a ligand-free Pd-catalyzed cascade consisting of isocyanide insertion into Ugi-tetrazole has been developed. The tetrazole precursor is prepared in one step by the Ugi-four component reaction. The reaction proceeds smoothly under mild conditions with high efficiency. This chemistry is simple, economical, and is believed to be the key step during the synthesis of significant pharmaceuticals. Graphical abstract image
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An efficient strategy for the synthesis of syn 1,3-diols via iterative acetate aldol reactions and synthesis of atorvastatin lactone ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Sandeep Goyal, Bhautikkumar Patel, Ratnesh Sharma, Mangilal Chouhan, Kapil Kumar, Mukesh Gangar, Vipin A. Nair An efficient strategy for the synthesis of syn 1,3-diol has been developed, employing an imidazolidinone based chiral auxiliary via stereoselective and sequential double acetate aldol reactions. The syn 1,3-diol subunit was modified to obtain the C-7 carboxylic acid side chain and further subjected to reaction with a suitable 1,4-diketone under Paal-Knorr conditions to obtain atorvastatin lactone. Graphical abstract image
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A facile synthesis of 2-(3-alkynyl-2,3-dihydrobenzofuran-3-yl)acetate ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Fengbin Song, Michael D. Gaul, William V. Murray A facile synthesis of 2-(3-alkynyl-2,3-dihydrobenzofuran-3-yl)acetate (1a, 1b), with a unique alkynyl-benzylic quaternary center on a dihydrobenzofuran ring, was accomplished. The key step of the synthesis is the aryl radical cyclization to the tethered enyne carboxylate to generate the unique alkynyl-benzylic quaternary center. The synthesis started from simple building blocks with high flexibility and constructed the complex template in a total of four steps. With several functional groups available, compounds of structure 1a and 1b could be easily further derivatized. Graphical abstract image
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Total synthesis of the proposed structure of decurrenside D ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Verónica González-Márquez, Silvano Cruz-Gregorio, Jacinto Sandoval-Lira, Leticia Quintero, Fernando Sartillo-Piscil A chiron approach for the total synthesis of the proposed structure of decurrenside D is reported. The construction of the 3-deoxy-d-manno-2-octulosonic acid framework (KDO derivative) was achieved by the transformation of the respective C-allylated-ribofuranose derivative into its corresponding α-keto acid ester derivative. Accordingly, the crucial step of this total synthesis is the application of the stereoselective nucleophilic substitution at the anomeric position (NSAP) reaction to the 5-O-benzoyl ribofuranose derivative. Both optical rotation and NMR data of the synthesized decurrenside D are inconsistent with the proposed structure. Graphical abstract image
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An analytical method for detecting toxic metal cations using cyclotriveratrylene derivative capped gold nanoparticles ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Zachary R. Osner, Richard C. Holz, Daniel P. Becker Cyclotriveratrylene-oxime (CTV-oxime) derivatives that terminate with a dithiolate linker were synthesized enabling the supramolecular scaffold to adhere to gold nanoparticles (AuNPs) with the bowl-shaped cavity of the CTV scaffold exposed for utilization in host–guest chemistry. Exposure of these CTV functionalized AuNPs to varying concentrations of di- and trivalent metal cations resulted in the formation of large CTV-AuNP polymeric clusters and an accompanying a shift in the plasmon resonance. These interactions between the CTV-AuNPs and the metal cations in solution provides proof-of-concept that supramolecular functionalized AuNPs can be used as a simple and straightforward, on-site detection system for toxic metal cations in solution. The order of binding affinity of the metals studied based on observed Kd values is Cu2+ >Zn2+ >Pb2+ >Hg2+ >Eu3+ >Cd2+. Graphical abstract image
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Solid-phase synthesis of fused 1,4-diazepanone peptidomimetics via tandem N-iminium ion cyclization–nucleophilic addition ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Pilar Ventosa-Andrés, Carlos Alfonso Barea Ripoll, Agustina La-Venia, Viktor Krchňák We herein describe the solid-phase synthesis of protected N-oxoalkyl-derivatized peptides designed for subsequent acid-mediated, tandem N-acyliminium ion cyclization–nucleophilic addition reaction. The target compounds contained fused 1,4-diazepanones incorporated into a peptide backbone and served as conformational constraints. The scope and limitation of the ring formation were studied, and the structural requirements and reaction conditions for cyclization are outlined. Graphical abstract image
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Expedient one-pot synthesis of indolo[3,2-c]isoquinolines via a base-promoted N-alkylation/tandem cyclization ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Huy H. Nguyen, James C. Fettinger, Makhluf J. Haddadin, Mark J. Kurth A transition metal-free, one-pot protocol has been developed for the synthesis of 11H-indolo[3,2-c]isoquinolin-5-amines via the atom economical annulation of ethyl (2-cyano-phenyl)carbamates and 2-cyanobenzyl bromides. This method proceeds via sequential N-alkylation and base-promoted cyclization. Optimization data, substrate scope, mechanistic insights, and photoluminescence properties are discussed. Graphical abstract image
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Four component DHARMA-synthesis of some densely functionalized 1,8-naphthyridines ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Ivan N. Bardasov, Anastasiya U. Alekseeva, Oleg V. Ershov, Mikhail Yu. Belikov We report the one-pot synthesis of the triethylammonium salts of 5,7-diamino-4-aryl-2-(dicyanomethyl)-1,4-dihydro-1,8-naphthyridine-3,6-dicarbonitriles from the reaction of aromatic aldehydes, a malononitrile dimer and triethylamine. Graphical abstract image
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Ozonation of benzotetrazine 1,3-dioxides. Facile synthesis of di(methoxycarbonyl)-1,2,3,4-tetrazine 1,3-dioxide ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Michael S. Klenov, Aleksandr M. Churakov, Yurii A. Strelenko, Ivan V. Ananyev, Konstantin A. Lyssenko, Vladimir A. Tartakovsky A new method for the synthesis of non-annulated 1,2,3,4-tetrazine-1,3-dioxides, proceeding via ozonation of benzotetrazine 1,3-dioxides bearing electron-donating substituents, followed by treatment with MeOH/HCl has been developed. Dimethyl 1,2,3,4-tetrazine-5,6-dicarboxylate 1,3-dioxide (4), methyl 5-(1,1-dichloro-2-ethoxy-2-oxoethyl)-1,2,3,4-tetrazine-6-carboxylate 1,3-dioxide (5) and methyl 6-formyl-1,2,3,4-tetrazine-5-carboxylate 1,3-dioxide (6) were prepared and the structures of tetrazines 4 and 5 were confirmed by X-ray diffraction analysis. Graphical abstract image
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Prodrugs of vitamin C: the reaction of 1-acyloxyalkyl-1-iodides with vitamin C 5,6-acetonide ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Jennifer McGowan, Nikki Thiele, Kenneth B. Sloan The reaction of 2equiv of 1-acyloxyalkyl-1-iodides with vitamin C 5,6-acetonide gave mixtures of products that were O-alkylated on the 3-position and either O-alkylated, 7, or O-acylated, 8, on the 2-position. The 8 products comprised the majority of the mixtures: 56:54 to 94:6. The 3-alkylated-2-acylated prodrugs, 8, hydrolyzed to vitamin C 5,6-acetonide chemically at pH 7.4 with half-lives of 6–12h. Graphical abstract image
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Reversible nucleophilic addition can lower the observed enantioselectivity in palladium-catalyzed allylic amination reactions with a variety of chiral ligands ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Nicholas S. Caminiti, Madison B. Goodstein, Isabelle N.-M. Leibler, Bryan S. Holtzman, Zitong B. Jia, Michael L. Martini, Nathaniel C. Nelson, Richard C. Bunt Palladium-catalyzed allylic amination is an important synthetic reaction that is also frequently used as a benchmark for the design and evaluation of new chiral ligands. The effect of reversible nucleophilic addition on the reaction of benzylamine with (E)-1,3-diphenylallyl ethyl carbonate (1) in CH2Cl2 was examined with 12 different chiral ligands across a range of scaffolding types. In 8 out of 12 cases the observed ee was significantly higher when DBU or Cs2CO3 was added to suppress the proton-driven reversibility. For chiral ligand screening with this test reaction, adding DBU or Cs2CO3 provides a better measure of the ligand’s inherent enantioselectivity. Graphical abstract image
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Palladium/copper tandem catalysis for carbon–carbon triple bond cleavage of diaryl acetylenes ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Zhiwei Wang, Wenyou Fan, Guo-Jun Deng, Wang Zhou A method for carbon–carbon triple bond cleavage based on palladium/copper tandem catalysis is developed. In this chemistry, anilines and diaryl acetylenes were converted into benzamides through cascade transformations combining palladium-catalyzed hydroamination of alkyne with copper-catalyzed aerobic oxidative C–C bond cleavage. Graphical abstract image
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Ningpoensines A–C: unusual zwitterionic alkaloids from Scrophularia ningpoensis ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Jun Zhang, Fanny C.F. Ip, Estella P.S. Tong, Kim Wan Chan, Liang-Chun Li, Yu Pong Ng, Nancy Y. Ip Three novel zwitterionic alkaloids—ningpoensine A (1) and a pair of epimers, ningpoensines B/C (2a/2b)—with unprecedented molecular skeletons were isolated from the root of Scrophularia ningpoensis. Their structures were established by extensive spectroscopic analyses, and the absolute configuration of ningpoensine A was determined by quantum chemical calculations. A biosynthetic pathway leading to ningpoensines A–C from harpagide and natural amino acids is proposed. Ningpoensines B/C tended to promote wound closure in human embryonic keratinocytes. Graphical abstract image
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(±)-Salviaprione, a pair of unprecedented abietane-type diterpeniods from Salvia prionitis ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Yong-Jun Jiang, Yu Zhang, Juan He, Xing-De Wu, Li-Dong Shao, Xiao-Nian Li, Jia Su, Li-Yan Peng, Rong-Tao Li, Qin-Shi Zhao (+)-Salviaprione and (−)-salviaprione, a pair of unprecedented abietane-type diterpeniods having an unprecedented 5/6/6 tricyclic ring system with a unique five membered ring A formed by a new C-2/C-11 bond, were isolated from the whole plant of Salvia prionitis. The enantiomeric separation was achieved by HPLC on a chiral column. Their structures and absolute configurations were determined on the basis of 1D and 2D NMR spectra, X-ray diffraction, and electronic circular dichroism (ECD). The possible biogenesis for (±)-salviaprione was also postulated. Graphical abstract image
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Asymmetric synthesis of common aza-tricyclic core of various alkaloids ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Ming Ding, Xiaogang Tong, Dashan Li, Kangjiang Liang, Ankun Zhou, Zhili Zuo, Chengfeng Xia The asymmetric synthesis of common aza-tricyclic core of different types of natural alkaloids had been accomplished from commercially available l-Cbz-tyrosine. This practical approach was capable of generating scale-up aza-tricyclic skeleton. Meanwhile, it will facilitate the manipulating functionalities on the aza-tricyclic framework further, for the purpose of target-oriented synthesis of a large number of different natural alkaloids containing this versatile aza-tricyclic structure. Graphical abstract image
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Synthesis and mesomorphic properties of novel columnar liquid crystals based on polytopic gallic ethers with multiple-hydrogen bonding cyanuric cores ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Hongyu Guo, Xiaoting Fang, Fafu Yang, Yamin Wu The gallic–cyanuric monomer 4, gallic–cyanuric dimer 5, gallic–cyanuric trimer 6 and gallic–cyanuric tetramer 7 containing multiple hydrogen bond were designed and synthesized in yields of 70–80%. Their symmetric structures were characterized by element analyses, FT-IR, ESI-MS, and NMR spectra. Their hexagonal columnar liquid crystalline phases were confirmed by DSC, POM, and XRD analyses. The scope of mesomorphic temperature of compounds 5, 6, and 7 is as wide as 45.7, 70.1, and 134.4°C, respectively. The more gallic ether units are favorable for excellent mesophase. Graphical abstract image
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The insertion of arynes into the O–H bond of aliphatic carboxylic acids ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Chunxiao Wen, Qian Chen, Zhenwen He, Xinxing Yan, Changyuan Zhang, Zhiyun Du, Kun Zhang The insertion of arynes into the O–H bond of aliphatic carboxylic acids promoted by sodium carboxylates is described. The reactions led to the formation of aryl carboxylates in good yields with good chemoselectivities under mild conditions. Graphical abstract image
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First total synthesis of antimalarial (+)-cryptorigidifoliol A ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Atla Raju, A. Yugendar Reddy, Gowravaram Sabitha The first total synthesis of antimalarial (+)-cryptorigidifoliol A was accomplished by two different approaches in 6 and 5 steps with overall yields of 45% and 33%, respectively. Double asymmetric allylations and ring-closing metathesis reaction in route A, Prins, and RCM in route B were used as key steps. Graphical abstract image
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Novel photochromic diarylethenes bearing an imidazole moiety ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Valerii Z. Shirinian, Andrey G. Lvov, Ekaterina Yu. Bulich, Alexey V. Zakharov, Mikhail M. Krayushkin Novel photochromic diarylethenes based on a 2,3-diarylcyclopent-2-en-1-one core and containing imidazole residues as the aryl moiety were synthesized. The photochromic properties of the obtained compounds were investigated in acetonitrile and a comparative analysis with oxazole and thiophene containing diarylethenes was performed. It was found that introduction of imidazole derivatives as the aryl moiety led to a significant decrease in thermal stability and an increase in both photosensitivity (quantum yields) and the bathochromic shift of the absorption maxima of both isomers. Graphical abstract image
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Corrigendum to ‘Stellettapeptins A and B, HIV-inhibitory cyclic depsipeptides from the marine sponge Stelletta sp.’ [Tetrahedron Lett. 56(28) (2015) 4215–4219] ()
Publication date: 30 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 40 Author(s): Hee Jae Shin, Mohammad A. Rashid, Laura K. Cartner, Heidi R. Bokesch, Jennifer A. Wilson, James B. McMahon, Kirk R. Gustafson
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Editorial board ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39
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Graphical Contents List ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39
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A new fusarielin analogue from Penicillium sp. isolated from the Mediterranean sponge Ircinia oros ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Huiqin Chen, Nihal Aktas, Belma Konuklugil, Attila Mándi, Georgios Daletos, Wenhan Lin, Haofu Dai, Tibor Kurtán, Peter Proksch The marine-derived fungus Penicillium sp. (strain IO1) isolated from the Mediterranean sponge Ircinia oros yielded a new fusarielin analogue (1) together with the known compounds griseofulvin (4) and dechlorogriseofulvin (5). The structure of 1 was unambiguously elucidated by comprehensive spectroscopic analysis (1D and 2D NMR, and mass spectrometry) as well as by comparison with the literature, while the absolute configuration of 1 was determined on the basis of TDDFT ECD calculations. A further Penicillium sp. (strain IO2) that was isolated from the same sponge I. oros yielded the known compounds dehydrocurvularin (6), curvularin (7), and trichodimerol (8). Co-cultivation of both Penicillium strains (IO1 and IO2) was found to induce the accumulation of the known norlichexanthone (2) and monocerin (3) that were not detected in either of the two axenic fungal controls. Compounds 3 and 6 showed pronounced cytotoxicity against the murine lymphoma (L5178Y) cell line with IC50 values of 8.4 and 4.7μM, respectively. Graphical abstract image
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An efficient total synthesis of (±)-ar-tenuifolene ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Adrián Vázquez-Sánchez, José Gustavo Ávila-Zárraga (±)-ar-Tenuifolene was synthesized using a ring expansion mediated by a formal 1,3-alkyl shift reaction on a trans-1-aryl-2-propenyl-cyclobutancarbonitrile as the key step to generating the cyclohexene moiety. The conditions for this rearrangement are described. Graphical abstract image
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Cyclization of an alkene-bearing cyclopentanone: The role of rhodium and Brønsted acid ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Xin Jiang, Zhongda Pan, Christopher J. Douglas The cyclization of an alkene-bearing cyclopentanone to a [2.2.1]-norcamphor ring system is described. The reaction is catalyzed by a combination of rhodium and Brønsted acid. Control experiments indicate that both are needed for acceptable yield. Control experiments with bulky base additives show that rhodium promotes alkene isomerization, likely the first step of this cascade reaction, and that rhodium alone does not promote cyclization. Cyclization is promoted by Brønsted acid in a Prins-type cyclization and carbocation rearrangement process. Trace Brønsted acid present in commercial samples of Rh(cod)2OTf is likely responsible for the observed reaction. Indeed, the norcamphor product can be obtained simply with strong acid, presumably initiated by acid-promoted alkene isomerization. Since our initial motivation for this work was the development of rhodium catalysts for the activation of C–C bonds adjacent to ketones, this communication serves to identify other, perhaps less obvious, pathways for the reactions of unsaturated ketone compounds by the action of rhodium catalysts. Graphical abstract image
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The p-toluenesulfonic acid-catalyzed transformation of polyfluorinated 2-alkynylanilines to 2-aminoarylketones and indoles ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Larisa Politanskaya, Vitalij Shteingarts, Evgeny Tretyakov, Alexander Potapov The reactivity of a series of polyfluorinated 2-alkynylanilines with various alcohols using p-TSA has been studied. It was found that hydration of the triple bond gave rise to polyfluorinated 2-aminoarylketones and competed with an electrophilic heterocyclization reaction leading to polyfluorinated indoles. The dependence of the reaction pathways on the nature of the alkynylaniline substituents has been examined. Graphical abstract image
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Pyrrolidine-containing peptides, JBIR-126, -148, and -149, from Streptomyces sp. NBRC 111228 ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Miho Izumikawa, Teppei Kawahara, Noritaka Kagaya, Hideki Yamamura, Masayuki Hayakawa, Motoki Takagi, Masahito Yoshida, Takayuki Doi, Kazuo Shin-ya New pyrrolidine containing peptides JBIR-126 (1), JBIR-148 (2), and JBIR-149 (3) were isolated from a culture of Streptomyces sp. NBRC 111228 obtained from soil collected in the Okinawa Prefecture, Japan. The planar structures of 1, 2 , and 3 were established based on 1D and 2D NMR, ESI-TOF-MS, IR, and UV spectra. The absolute configurations of amino acid residues were determined by Marfey’s method. Compounds 1, 2 , and 3 are structurally related to JBIR-34 and -35, in which an alanine residue is replaced by a unique pyrrolidine moiety. Graphical abstract image
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Synthesis of novel cyano quinoline derivatives ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Salih Ökten, Osman Çakmak 6,8-Dibromo-1,2,3,4-tetrahydroquinoline (2) and 3,6,8-tribromoquinoline (3) were converted into the corresponding cyano derivatives via copper assisted nucleophilic substitution reactions. While bromination of 6-bromo-8-cyanotetrahydroquinoline (11) gave 3,6-dibromo-8-cyanoquinoline (8), the reaction of dicyano-1,2,3,4-tetrahydroquinoline (12) resulted in the formation of an unexpected dimer (15). Graphical abstract image
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A simple synthesis of anilines by LiAlH4/TiCl4 reduction of aromatic nitro compounds ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Maria Luisa Di Gioia, Antonella Leggio, Isabella Federica Guarino, Vanessa Leotta, Emanuela Romio, Angelo Liguori A rapid and efficient single-step synthesis of substituted anilines has been developed. The aromatic nitro compounds were reduced by using reducing systems generated by the action of an excess of LiAlH4 on TiCl4. Anilines substituted with different functional groups were synthesized in high yields and purity starting from the corresponding nitro compounds. The developed procedure is applicable to nitroaromatics containing both electron withdrawing and electron donating substituents. Substrates with electron donor substituents require a larger excess of LiAlH4. The reducing power of the prepared reactant systems depends on the used molar ratio of LiAlH4 and TiCl4. Graphical abstract image
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Total synthesis and complete stereochemical assignment of heronapyrroles A and B ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Tomoki Matsuo, Subaru Hashimoto, Keisuke Nishikawa, Takeshi Kodama, Seiho Kikuchi, Yoshimitsu Tachi, Yoshiki Morimoto Heronapyrroles A and B with promising and selective antibacterial activity but no cytotoxicity against mammalian cell lines are among members of rare and unique 4-farnesylated-2-nitropyrrole natural products. The absolute configurations at C7 and C15 have been proposed to be 7S and 15R by the modified Mosher method. In this Letter, we have achieved the total synthesis of natural (+)-heronapyrroles A (1) and B (2) and report that the correct absolute configurations are 7R, 8S, and 15S as shown in the structural formulas 1 and 2. Graphical abstract image
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Convenient synthesis of 2-alkynylbenzazoles through Sonogashira cross-coupling reaction between thioethers and terminal alkynes ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Anca Paun, Mihaela Matache, Florina Enache, Ioana Nicolau, Codruta C. Paraschivescu, Petre Ionita, Irina Zarafu, Vasile I. Parvulescu, Gérald Guillaumet We describe herein the synthesis of 2-alkynylbenzoxazole and 2-alkynylbenzothiazole derivatives through the Sonogashira cross-coupling reaction of the corresponding thioethers and terminal alkynes under aerobic conditions, using CuI and Pd(dppf)Cl2 as catalysts. The synthetic methodology allows the convenient cross-coupling of heteroaromatic substrates with a wide variety of aromatic and aliphatic alkynes, in moderate to good yields. The behavior of mercapto benzoxazoles and benzothiazoles were also investigated in the desulfitative Sonogashira cross-coupling reaction. It is noteworthy that the reaction occurred better under aerobic conditions rather than an inert atmosphere, although with increased amounts of the diyne side-product. Graphical abstract image
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Identification and synthesis of the male produced volatiles of the carrion beetle, Oxelytrum erythrurum (Coleoptera: Silphidae) ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): Douglas H. Fockink, Camila B.C. Martins, Paulo H.G. Zarbin Necrophagous beetles belonging to the family Silphidae are recognized as potentially useful in forensic investigations (to estimate post mortem interval). Gas chromatography analyses of extracts of aerations of adult Oxelytrum erythrurum revealed the presence of two male-specific compounds. These compounds were identified as (Z)-1,10-nonadecadiene (major) and 1-nonadecene (minor) using microderivatizations of the natural male extract, such as hydrogenation, partial reduction and methylthiolation, mass spectrum comparisons, and co-injections with authentic standards. Both compounds might be components of a pheromone responsible for sexual communication in this species. Graphical abstract image
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Direct C–H azidation of calix[4]arene as a novel method to access meta substituted derivatives ()
Publication date: 23 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 39 Author(s): František Stejskal, Václav Eigner, Hana Dvořáková, Petra Cuřínová, Pavel Lhoták A novel method for the regioselective meta substitution of calix[4]arenes based on the direct C–H azidation of an amino-substituted calixarene immobilized in the cone conformation is described. Reaction with trimethylsilyl azide and tert-butyl hydroperoxide in the presence of CuBr as a catalyst, provided, depending on the stoichiometry, mono- or bis-azide-substituted derivatives in good yields under mild reaction conditions. meta-Azido calixarenes represent potentially valuable synthetic intermediates for the preparation of calixarenes possessing unusual substitution patterns as demonstrated by a click reaction with p-nitrophenyl acetylene. Graphical abstract image
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Editorial board ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38
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Graphical Contents List ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38
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Application of catalytic Z-selective olefin metathesis in natural product synthesis ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): Simon Werrel, Johannes C.L. Walker, Timothy J. Donohoe Over the last few years, a number of olefin metathesis catalysts have been disclosed that enable the synthesis of energetically disfavoured Z-alkenes. The application of this method to the synthesis of complex natural products has driven the development of new catalysts and furthered the understanding of their behaviour and reactivity. This digest discusses the progress made and highlights the benefits of this chemistry over more traditional protocols. Graphical abstract image
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Chiral aziridine ring opening: facile synthesis of (R)-mexiletine and (R)-phenoxybenzamine hydrochloride ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): N. Viswanadh, R. Velayudham, S. Jambu, M. Sasikumar, M. Muthukrishnan A simple and efficient synthesis of chiral drugs (R)-mexiletine 1, an anti-arrhythmic drug and (R)-phenoxybenzamine hydrochloride 2, an anti-hypertensive drug has been described via controlled reductive ring opening of chiral aziridine as a key step. The target compounds 1 and 2 were obtained in overall yields of 34% and 10.5%, respectively. Graphical abstract image
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The introduction of P–F bonds using aqueous fluoride ion and a water soluble carbodiimide: a convenient alternative synthesis of phosphorofluoridates and phosphonofluoridates ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): Michael F. Aldersley, Prakash C. Joshi, Elizabeth L. Ott, Scott A. McCallum, Anthony J. Kirby The chemistry of ribonucleotides and other phosphates is extended to include their reactions with potassium fluoride in aqueous solution in the presence of a water soluble carbodiimide. High yields (>98%) of phosphorofluoridates are formed. A combination of HPLC, mass spectrometry, and NMR confirms the identities of the products. The methodology is applied, with equally satisfactory outcomes, to the physiologically active phosphonates Adefovir® and Tenofovir®, providing new compounds. Detailed NMR studies of the new phosphonofluoridates are reported. Graphical abstract image
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Synthesis of substituted pyridines from 1,2-nucleophilic addition products of functionalized N-acyl-2,3-dihydropyridones ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): Mustafa Guzel, Joshua Watts, Matthew McGilvary, Marcus Wright, Sezgin Kiren We describe herein a general and efficient synthetic approach toward substituted pyridines from functionalized N-acyl-2,3-dihydropyridones in two steps; 1,2-addition with organocerium reagents and subsequent oxidative aromatization with chloranil. This strategy allows the generation of pyridines with various substitution patterns and introduces a variety of substituents including aryl, alkyl, alkynyl, alkenyl, and heteroaryl groups at the desired positions. Graphical abstract image
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Nonstabilized azomethine ylides as reagents for alkylaminomethylation of aromatic ketones via 5-aryloxazolidines ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): Vladimir S. Moshkin, Evgeny M. Buev, Vyacheslav Y. Sosnovskikh Aromatic ketones were found to react smoothly with nonstabilized azomethine ylides, generated in situ from sarcosine/formaldehyde or N-(methoxymethyl)-N-(trimethylsilylmethyl)benzylamine, to give 5-aryloxazolidines which were converted into 2-alkylaminoethanols in moderate to good yields by heating in n-butanol with hydrochloric acid. Graphical abstract image
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Rhodium(III)-catalyzed internal oxidative coupling of N-hydroxyanilides with alkenes via C–H activation ()
Publication date: 16 September 2015 Source:Tetrahedron Letters, Volume 56, Issue 38 Author(s): Jing Wen, An Wu, Pei Chen, Jin Zhu Described herein is an efficient new method for ortho-olefination of anilides in the presence of AgSbF6 and NaOAc via rhodium(III)-catalyzed internal oxidative C–H bond activation based on hydroxyl as directing and oxidative group. A range of alkenes and functional groups on acetanilides is supported and a possible mechanism is proposed according to the experimental results. Graphical abstract image
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