pinecone/core-2020-05-10-deduplication huggingface dataset:
Facile synthesis and structure of novel 2,5-disubstituted 1,3,4-selenadiazoles

This work is funded by EPSRC UKThe reaction of hydrazide with carbonyl chloride in the presence of sodium carbonates leads to the corresponding 1,2-diacylhydrazines [ 1a – t , R1C(O)NHNHC(O)R2, R1 = aryl, R2 = aryl or alkyl] in moderate to excellent yield (57–90 %). The latter reacts with 2,4-diphenyl-1,3-diselenadiphosphetane-2,4-diselenide (Woollins' reagent, WR ) in refluxing toluene to give a series of new 2,5-disubstituted 1,3,4-selenadiazoles ( 2a – t , 51–99 % yield). All compounds were characterized spectroscopically and six compounds were characterized crystallographically.PostprintPeer reviewe
A Tetrakis(tetrazolyl) Analogue of EDTA

International audienceThe tetrazole moiety is usually established in situ with the corresponding inconveniences, such as reactant incompatibility, yield. In most of these cases, the tetrazole is formed in its nonprotected form. Subsequent protection is unattractive because of the promiscuous formation of two regioisomers. No particular protecting group has seen widespread use. The growing field of site-selective oxidation of unactivated hydrocarbons makes use of metal complexes based on multidentate ligands displaying nitrogen coordination sites. We have characterized an easily accessible, benzyl-protected synthon that allows the convergent introduction of the tetrazolylmethyl moiety and its smooth deprotection by catalytic hydrogenation. With the straightforward synthesis of the new hexadentate ligand EDTT, we have demonstrated the utility of this synthon for the fields of coordination, medicinal, and organocatalytic chemistry
Synthesis and photophysical studies of a pyrenylindole and a phenalenoindole obtained from dehydroamino acid derivatives : application as fluorescent probes for biological systems

Two pyrenyl-dehydroamino acid derivatives were cyclized by a metal-assisted C–N intramolecular cyclization developed in our research group, to give a pyrenylindole and a phenalenoindole. The pyrenylindole was inserted into a peptide by solid-phase coupling, with use of a 2-chlorotrityl chloride resin and a Fmoc strategy. The photophysical properties of the pyrenylindole and phenalenoindole in several solvents were studied and showed that these compounds can be used as fluorescence probes. The results obtained with the peptide labelled with the pyrenylindole moiety show potential for use of this compound as a fluorescence label avoiding the aggregation propensity of pyrene compounds. Photophysical studies of the pyrenylindole and of the phenalenoindole in lipid membranes were also carried out. Steady-state fluorescence anisotropy measurements revealed that both compounds adopt locations inside the lipid bilayers and are able to report the transition between the gel and liquid-crystalline phases. The results point to potential use of these compounds as fluorescent
probes for biological systems.Fundação para a Ciência e a Tecnologia (FCT) - (SFRH/BPD/24548/2005),  (SFRH/BD/38766/2007)Fundo Europeu de Desenvolvimento Regional
(FEDER) - Project PTDC/QUI/81238/200
Synthesis of prolines by enantioselective 1,3-dipolar cycloaddition of azomethine ylides and alkenes catalyzed by chiral phosphoramidite-silver(I) complexes

The endo-diastereo- and enantioselective 1,3-dipolar cycloaddition of azomethine ylides and electrophilic alkenes is efficiently catalysed by chiral phosphoramidite-silver(I) perchlorate complexes. The reaction allows the presence of different types of substituents in the 1,3-dipole and can be applied to the synthesis of enantiomerically enriched, highly substituted prolines. This methodology was applied to the total synthesis of the inhibitors of the hepatitis C virus (HCV). Computational studies support a two-step mechanism predicting exactly the experimental results and the origin of both the diastereo- and enantioselections, as well as a reasonable explanation concerning the different reaction rates observed for some substrates.This work was supported by the DGES of the Spanish Ministerio de Educación y Ciencia (MEC) (Consolider INGENIO 2010 CSD2007-00006, CTQ2007-62771/BQU and CTQ2004-00808/BQU) and by the University of Alicante
Wittig-type olefination of alcohols promoted by nickel nanoparticles: synthesis of polymethoxylated and polyhydroxylated stilbenes

Nickel nanoparticles were found to promote the Wittig-type olefination of primary alcohols with phosphorus ylides. The latter can be prepared from the corresponding phosphonium salts with nBuLi or in situ generated with lithium metal. The methodology is especially efficient for the synthesis of stilbenes and is applied in the absence of any additive as ahydrogen acceptor. A new approach to the synthesis of polymethoxylated and polyhydroxylated stilbenes, including resveratrol, DMU-212 and analogues, is presented.Spanish Ministerio de Educación y Ciencia (MEC); Grant Number: CTQ2007-65218, CSD2007-00006
Iso-seco-tanapartholides : isolation, synthesis and biological evaluation

The isolation, identification and total synthesis of two plant-derived inhibitors of the NF-kappa B signaling pathway from the iso-seco-tanapartholide family of natural products is described. A key step in the efficient reaction sequence is a late-stage oxidative cleavage reaction that was carried out in the absence of protecting groups to give the natural products directly. A detailed comparison of the synthetic material with samples of the natural products proved informative. Biological studies on synthetic material confirmed that these compounds act late in the NF-kappa B signaling pathway. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)Publisher PDFPeer reviewe
Unsupported copper nanoparticles in the 1,3-dipolar cycloaddition of terminal alkynes and azides

Readily prepared copper nanoparticles were found to catalyse the 1,3-dipolar cycloaddition of azides and alkynes up to rates comparable to those of microwave chemistry. Both the preparation of the nanoparticles and the click reaction are carried out under mild conditions, in short reaction times and in the absence of any stabilising additive or ligand. A variety of 1,2,3-triazoles were prepared in excellent yields. A reaction mechanism was postulated on the basis of different reactivity studies and deuteration experiments. Copper(I) acetylides were demonstrated to be the real intermediate species.Spanish Ministerio de Educación y Ciencia (MEC) (grant no. CTQ2007-65218 and Consolider Ingenio 2010-CSD2007-00006), the Generalitat Valenciana (grant no. PROMETEO/2009/039) and the Secretaría General de Ciencia y Tecnología (SeCyT), Universidad Nacional del Sur (PGI 24/Q014)
Novel five- to ten-membered organoselenium heterocycles from the selenation of aromatic diols

This work is funded by the EPSRC UKReaction of Woollins' reagent ― WR , 2,4-bis(phenyl)-1,3-diselenadiphosphetane 2,4-diselenide [{PhP(Se)(μ-Se)}2] ― with aromatic diols in refluxing toluene afforded a series of novel five- to ten-membered phosphorus-selenium heterocycles 1 – 10 with an O–P(Se)–O or O–P(Se)–Se–P(Se)–O or O–P(Se)–O–P(Se)–O linkage in 12–74 % isolated yields. It was found that the diphosphorus species O–P(Se)–Se–P(Se)–O rings could be readily reduced into the monophosphorus species O–P(Se)–O rings in almost quantitative yields via further reaction with another equivalent of corresponding aromatic diol. All new compounds have been characterized by IR, 1H NMR, 13C NMR, 31P NMR, 77Se NMR, mass spectrometry and elemental analysis or accurate mass measurement. Seven representative X-ray structures are reported.PostprintPeer reviewe
A cyclic porphyrin tetramer linked by azo and butadiyne bridges

A soluble cyclic porphyrin oligomer (CPO) consisting of four 5,10-\ud
diarylporphyrins linked by alternating azo and butadiyne bridges has been synthesised via an\ud
aminated dinickel(II) butadiyne dimer. This is the first cyclic tetramer that combines both azo\ud
and butadiyne bridges and extends the azoporphyrin family, which comprises only a very few\ud
examples. The electronic absorption spectrum of the tetramer is more similar to spectra of\ud
azoporphyrins than to those of butadiyne-linked dimers or tetramer, exhibiting a two component\ud
Soret band with a splitting of 4190 cm-1 and a strongly red-shifted Q band\ud
maximum at 735 nm
Systematic study of halide-induced ring opening of 2-substituted aziridinium salts and theoretical rationalization of the reaction pathways

The ring-opening reactions of 2-alkyl-substituted 1,1-bis(arylmethyl)- and 1-methyl-1-(1-phenylethyl)aziridinium salts with fluoride, chloride, bromide and iodide in acetonitrile have been evaluated for the first time in a systematic way. The reactions with fluoride afforded regioisomeric mixtures of primary and secondary fluorides, whereas secondary β-chloro, β-bromo and β-iodo amines were obtained as the sole reaction products from the corresponding halides by regiospecific ring opening at the substituted position. Both experimental and computational results revealed that the reaction outcomes in the cases of chloride, bromide and iodide were dictated by product stability through thermodynamic control involving rearrangement of the initially formed primary halides to the more stable secondary halides. The ring opening of the same aziridinium salts with fluoride, however, was shown to be mediated by steric interactions (kinetic control), with the corresponding primary β-fluoro amines being obtained as the main reaction products. Only for 2-acylaziridinium ions was the reaction outcome shown to be under full substrate control, affording secondary β-fluoro, β-chloro, β-bromo and β-iodo amines through exclusive attack at the activated α-carbonyl carbon atom
Brønsted Acid Catalyzed Alkylation of Indoles with Tertiary Propargylic Alcohols: Scope and Limitations

Direct alkylation of indoles with a wide variety of tertiary propargylic alcohols under Brønsted acid catalysis conditions has been studied. A general and environmentally friendly method for the synthesis of 3-propargylated indoles with quaternary carbon atoms at their propargylic positions has been developed. The reactions are highly regioselective with regard both to the indole and to the alkynol components. Only with N-unsubstituted 2-arylindoles do competitive SN′ reactions take place to afford 3-dienyl- or 3-allenylindoles, depending on the alkynol moiety. The reactions were carried out in air with undried solvents, and water was the only side product.Junta de Castilla y Leon (BU021A09 and GR-172) and the Ministerio de Educacion y Ciencia (MEC) and FEDER (CTQ2007-61436/BQU and CTQ2009-09949/BQU) for financial support. D. M. and A. M. thank the MEC for MEC-FPU predoctoral fellowships. M. G. thanks the MEC for a "Young Foreign Researchers" contract (SB2006-0215). M. A. F.-R. and P. G.-G. also thank the MEC for "Ramon y Cajal" and "Juan de la Cierva" contracts.This is the pre-peer reviewed version of the following article: Sanz, R., Miguel, D., Martínez, A., Gohain, M., García-García, P., Fernández-Rodríguez, M. A., Álvarez, E. and Rodríguez, F. (2010), Brønsted Acid Catalyzed Alkylation of Indoles with Tertiary Propargylic Alcohols: Scope and Limitations. Eur. J. Org. Chem., 2010: 7027–7039. doi: 10.1002/ejoc.201001055, which has been published in final form at 10.1002/ejoc.201001055. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
Synthesis of the macrolactone of migrastatin and analogues with potent cell-migration inhibitory activity

The synthesis of the macrolactone core of migrastatin 2, its potent anti-metastasis analogue 34, and ester derivatives 35 and 38 are reported. The approach involves the use of a dihydroxylation reaction to establish the desired C-8 stereocenter followed by a metathesis cyclization reaction. The effects of the compounds on the migration and invasion of human breast cancer cells were evaluated by using the wound-healing and the Boyden-chamber cell-migration and cell-invasion assays. The results revealed a high potency of the macrolactones 2 and 34 and the ester analogues 35 and 38, which suggests they have potential as antimetastatic agents.Fundo de Apoio ao Ensino e Pesquisa da UNICAMP (FAEP-UNICAMP)FAPESPCNPqInstituto Nacional de Ciência e Tecnologia de Fármacos e Medicamentos (INCT-INOFAR
N-(Di)icosyl-substituted benzo[a]phenoxazinium chlorides : synthesis and evaluation as near-infrared membrane probes

Five benzo[a]phenoxazinium chlorides containing alkyl chains with twenty carbon atoms on 5- or 9-positions of the tetracyclic ring were efficiently synthesised and characterised by UV/Vis/NIR spectroscopy. The absorption and emission maxima in ethanol lie in the range 627-641 nm and 645-676 nm, respectively, with quantum yields varying from 0.14 to 0.38. Preliminary photophysical studies with these fluorochromophores in zwitterionic (2,3- bis(palmitoyl-oxy)propyl-2-(trimethylammonio)ethyl phosphate, DPPC) and cationic (N,N-dimethyl-N-octadecyloctadecan-1-aminium bromide, DODAB) vesicles were carried out. The results showed that the new benzo[a]phenoxazinium derivatives are able to detect the gel to liquid-crystalline lipid phase transition through variations, either in the H-aggregation extent or in an acid-base equilibrium.Fundação para a Ciência e Tecnologia (FCT) - REDE/1517/RMN/2005Fundo Europeu de Desenvolvimento Regional (FEDER) - POCI 201
Access to the cis-fused stereoisomers of proline analogues containing an octahydroindole core

El pdf del artículo es la versión post-print.An overview of the synthetic methods developed to build all the cis-fused stereoisomers of octahydroindole-2-carboxylic acid and its α-methylated derivative in enantiomerically pure form is presented. Both asymmetric synthetic strategies(auxiliary- or substrate-controlled processes) and procedures based on the resolution of racemic compounds (chemical, enzymatic, and chromatographic processes) are summarized. Special emphasis has been placed on those strategies able to provide multigram quantities of enantiopure compounds, a prerequisite to make downstream biological applications feasible.Financial support from the Ministerio de Ciencia e Innovación (projects CTQ2007-62245 and CTQ2010-17436; predoctoral fellowship for P. L.) and the Gobierno de Aragón (project PIP206/ 2005 and research group E40) is gratefully acknowledged.Peer Reviewe
Homocoupling of terminal alkynes catalysed by ultrafine copper nanoparticles on titania

Copper nanoparticles on titania effectively catalyse the oxidative homocoupling of terminal alkynes in the presence of piperidine as a base in tetrahydrofuran (THF) or under solvent-free conditions. A wide range of diynes have been synthesised in high yields using low catalyst loading (1 mol-% Cu). The copper catalyst (mainly as Cu2O) has been characterised by different means, is easy to prepare, can be reutilised several times, works either in air or under inert atmosphere and was shown to be superior to other commercially available copper sources.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación [(MICINN) (grant number CTQ2007-65218) and Consolider Ingenio (grant number 2010-CSD2007-00006)], the Generalitat Valenciana (grant no. PROMETEO/2009/039), and the Fondos Europeos para el Desarrollo Regional (FEDER)
Synthesis of the 5 '-fluoro-2 'beta-methyl analogues of neplanocin

Synthesis of the 5'-fluoro-2'-beta-methyl analogues of neplanocin was carried out. Key intermediate cyclopentenone 19 was prepared from methyl alpha-D-mannopyranoside by a new approach consisting of ring-closing metathesis, stereoselective introduction of the 2'-methyl group, and intramolecular oxyselenenylation of the double bond as representative steps. Subsequent introduction of a fluorine atom at the 5'-position of 19 was performed by electrophilic fluorination by using Selectfluor.status: publishe
Asymmetric Synthesis of New beta-Lactam Lipopeptides as Bacterial Signal Peptidase I Inhibitors

The transmembrane bacterial enzyme, signal peptidase I, is recognized as being a promising target for reducing the emergence of drug resistance. The asymmetric synthesis and the biological evaluation of original beta-lactam lipopeptides have been performed to discover potent signal peptidase inhibitors. The importance of the azetidinone motif of these lipopeptides has been demonstrated and can serve as a starting point to exploit and improve the reactivity of the beta-lactam in peptidomimetics.status: publishe
Stereodivergent Synthesis of Two Novel α-Aminophosphonic Acids Characterised by a cis-Fused Octahydroindole System

The synthesis of two new α-aminophosphonic acids, namely (2S*,3aS*,7aS)- and (2R*,3aS*,7aS)-octahydroindole-2- phosphonic acids, is described. They are analogues of phosphoproline with a cyclohexane ring fused to the pyrrolidine moiety. The ring junction has cis stereochemistry in both cases, but the two compounds differ in the relative orientation of the cyclohexane and phosphonate moieties. The two amino acids were prepared from a common starting material following stereodivergent routes that provide the desired stereoisomer with complete stereocontrol. The relative configurations of the compounds synthesised were confirmed by X-ray diffraction analysis. Two analogues of phosphoproline with a cyclohexane ring fused to the pyrrolidine moiety have been synthesised. They differ in the stereochemistry at the α-carbon atom and have been prepared, with complete stereocontrol, following stereodivergent routes from a common precursor.The authors thank the Ministerio de Ciencia e Innovación (project CTQ2010-17436), the Consejo Superior de Investigaciones Científicas (project 2008MX0044; JAE predoctoral fellowship to A. A.), the Gobierno de Aragón (group E40) and the Consejo Nacional de Ciencia y Tecnología (CONACYT-MEXICO; projects 62271 and J000.400/2009) for financial support.Peer Reviewe
Enhanced Efficiency of Thiourea Catalysts by External Brønsted Acids in the Friedel–Crafts Alkylation of Indoles

A novel study on the influence of external Brønsted acids on thiourea catalysts in the asymmetric Friedel–Crafts alkylation of indoles with nitroalkenes is reported. The final 3-substituted indole derivatives were synthesized with better results because of cooperative effects between the chiral thiourea and a Brønsted acid additive (1a·HA). The effects of diverse catalysts, different acid additives, solvents, and temperatures in the reaction were also explored. The high reactivity and selectivity of the reaction is presumptively attributed to an appropriate assembly between the Brønsted acid and the thiourea structure, affording a more acidic and rigid catalytic complex.We thank the Ministry of Science and Innovation (MICINN), Madrid, Spain (Project CTQ2010-19606), and the Government of Aragón, Zaragoza, Spain (Project PI064/09 and Research Groups, E-10), for financial support of our research. E.M.-L. thanks CSIC for a JAE-Doc postdoctoral contract.Peer Reviewe
Synthesis of new n-ethyl dehydroamino acid derivatives : n-ethyl β,β-dibromo, n-ethyl β-bromo β-substituted, n-ethyl β,β-disubstituted n-protected dehydroamino acid methyl esters

Recently we reported the use of a sequence of alkylation and dehydration methodologies to obtain from the methyl esters of N-(4-nitrophenylsulfonyl)-β-hydroxyamino acids, new non-proteinogenic amino acids, namely, N-ethyl-α,β-dehydroamino acids. Thus, it was possible to obtain for the first time, non-natural amino acids which incorporate both the N-ethyl and α,β-dehydro moieties. Herein, we report the application of this N-alkylation procedure to several methyl esters of β,β-dibromo and β-bromo,  β-substituted  dehydroamino  acids  protected with standard  amine protecting groups such as tert-butyloxycarbonyl, benzyloxycarbonyl and 4-nitrobenzyloxycarbonyl as well as acyl and sulfonyl groups. The procedure allows the synthesis of the methyl esters of N-protected, N-ethyl, β,β-dibromo and N-ethyl, β-bromo, β-substituted dehydroamino acids in fair to high yields. Some of these N-ethylated dehydroamino acid derivatives were used as substrates in cross coupling reactions to give N-ethyl, β,β-disubstituted dehydroalanine derivatives.The Portuguese Foundation for Science and Technology (FCT) and the Fundo Europeu de Desenvolvimento Regional (FEDER) are thanked for financial support to the Chemistry Centre of University of Minho. The Bruker Avance II<SUP>+</SUP> 400 NMR spectrometer is part of the National NMR Network and was purchased in the framework of the National Program for Scientific Re-equipment, REDE/1517/RMN/2005, with funds from POCI 2010, FEDER and FCT
Synthesis of perhydrofuro[2,3-b]furans from isopentenyl alcohol through carbonyl-ene and wacker-type reactions

A range of 2-substituted perhydrofuro[2,3-b]furans have been synthesized in a stereoselective manner through a sequence involving the Lewis-acid catalyzed carbonyl-ene reaction of a protected isopentenyl alcohol with a variety of enophiles, deprotection of the corresponding monoprotected diols, and palladium-catalyzed intramolecular acetalization under Wacker-type reaction conditions.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación (MICINN), grant number CTQ2007-65218 and Consolider Ingenio 2010, grant number CSD2007-00006, the Generalitat Valenciana (GV; PROMETEO/2009/039), and Fondos Europeos para el Desarrollo Regional (FEDER). D. S. thanks the Vicerrectorado de Investigación, Desarrollo e Innovación of the Universidad de Alicante for a predoctoral grant. M. R.-F. thanks the ISO of the Universidad de Alicante for a postdoctoral grant
Looking for a robust, synthetic, fully-extended (2.05-Helical) Peptide Structure - Effect of Terminal Groups

The incorporation of α-amino acids with a quaternary α-carbon\ud
atom into a peptide provides a tool to effectively restrict\ud
the available range of its backbone conformations. Specifically,\ud
under favorable conditions, Cα,α-diethylglycine (Deg)\ud
homopeptides are known to preferentially adopt the fullyextended\ud
(2.05-helical) structure, which is characterized by the longest possible separation between two adjacent α-\ud
amino acid Cα atoms. We have investigated the influence of\ud
the nature of the N- and/or C-terminal protecting (or blocking)\ud
groups on the relative stabilities of the fully-extended\ud
conformation vs. the competing, shorter 310-helical structure\ud
in a synthetic Deg homopeptide series
Three-component coupling of aldehydes, amines and alkynes catalyzed by oxidized copper nanoparticles on titania

Copper nanoparticles (mainly as Cu2O) on titania have been shown to catalyze the multicomponent synthesis of propargylamines from aldehydes, amines, and alkynes (A3 coupling) effectively at 70 °C under solvent-free conditions. Both aromatic and aliphatic aldehydes and alkynes have been combined with secondary amines to provide a wide range of propargylamines in moderate to excellent yields. Two examples of ketone/amine/alkyne (KA2) coupling are also included. The catalyst is easy to prepare, reusable at a low copper loading (0.5 mol-%), and exhibits higher catalytic activity than some commercially available copper sources. Some mechanistic aspects of the reaction have also been examined, which have unveiled the participation of copper(I) acetylides in a heterogeneous process.This work was generously supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) (grant numbers CTQ2007-65218, CTQ2011-24151), Consolider Ingenio (grant number 2010-CSD2007-00006), the Generalitat Valenciana (grant number PROMETEO/2009/039), and Fondos Europeos para el Desarrollo Regional (FEDER). Y. M. and M. J .A. acknowledge the ISO of the Universidad de Alicante for a grant