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Organic & Biomolecular Chemistry

Ivo E Sampaio-Dias, Carlos A D Sousa, Sara C Silva-Reis, Sara Ribeiro, Xerardo García-Mera, José E Rodríguez-Borges
This study describes a methodological advancement in solution-phase peptide synthesis via the development of a convenient and operational protocol to synthesize oligopeptides in a one-pot three-step cascade method, in which two peptide bonds are introduced chemoselectively. Tri- to hexapeptides were obtained in high global yields (80-95%) with virtually no epimerization as determined via HPLC. The methodology described herein represents a faster, easier and milder approach to the synthesis of peptides, and it operates at equimolar amounts...
August 22, 2017: Organic & Biomolecular Chemistry
Yoshinosuke Usuki, Chie Hamada, Tetsuya Satoh
First total syntheses of JBIR-04 and unantimycin A have been achieved. Comparison of our spectroscopic data with those reported for natural samples verified the structure of the natural products; (2S,4S,6S,7R,9S,28S) configuration was thus assigned via total synthesis.
August 22, 2017: Organic & Biomolecular Chemistry
Haojie Ma, Xiaoqiang Zhou, Zhenzhen Zhan, Daidong Wei, Chong Shi, Xingxing Liu, Guosheng Huang
Copper catalyzed chemoselective cleavage of the C(CO)-C(alkyl) bond leading to C-N bond formation with chelation assistance of N-containing directing groups is described. Inexpensive Cu(ii)-acetate serves as a convenient catalyst for this transformation. This method highlights the emerging strategy to transform unactivated alkyl ketones into amides in organic synthesis and provides a new strategy for C-C bond cleavage.
August 22, 2017: Organic & Biomolecular Chemistry
Carlos E Gutierrez-Ulloa, Marina Yu Buyanova, Evgeny K Apartsin, Alya G Venyaminova, F Javier de la Mata, Mercedes Valiente, Rafael Gómez
A novel family of amphiphilic ionic carbosilane dendrons containing fatty acids at the focal point were synthesized and characterized. They spontaneously self-assembled in aqueous solution into micelles both in the absence and presence of salt, as confirmed by surface tension, conductivity, and DLS measurements. Dendron based micelles have spherical shapes and increase in size on decreasing dendron generation. These dendritic micelles have been demonstrated to be able to form complexes with therapeutic macromolecules such as siRNA and show a high loading capacity for drugs such as procaine, suggesting their potential use as nanocarriers for therapeutics...
August 22, 2017: Organic & Biomolecular Chemistry
Mukund M D Pramanik, Savita B Nagode, Ruchir Kant, Namrata Rastogi
The present work documents the α-C-H functionalization of tertiary amines via the visible light catalyzed Mannich reaction with silyl diazoenolates. The reaction takes place at room temperature with an organic dye, Rose Bengal, as a photocatalyst and oxygen as the oxidant. The resulting multifunctional products bearing an α-diazo-β-keto group undergo Rh-carbenoid mediated cyclization, affording stable ammonium ylides in high yields.
August 22, 2017: Organic & Biomolecular Chemistry
Andrea Savoldelli, Roberto Paolesse, Frank R Fronczek, Kevin M Smith, M Graça H Vicente
Asymmetric dimers of BODIPY dyes were synthesized from a,c-biladiene salts in good yields; this work constitutes a new versatile approach to the synthesis of BODIPY dyads, which display red-shifted absorptions and emissions in the visible spectral region, higher fluorescence quantum yields and larger Stokes shifts compared with monomeric BODIPYs. The X-ray structure of a 5,5'-dibromo-BODIPY dyad was obtained, and the reactivity of this compound under Suzuki cross-coupling reaction conditions was investigated...
August 22, 2017: Organic & Biomolecular Chemistry
Yan-Qin Yuan, Pailla Santhosh Kumar, Chun-Niu Zhang, Ming-Hua Yang, Sheng-Rong Guo
A highly effective oxidative thiyl radical addition/cyclization of N-methacryloylbenzamides was explored using dioxygen as the sole terminal oxidant without the use of precious and/or toxic transition-metal catalysts. This method provides convenient access to a variety of useful sulfide-containing 4,4-disubstituted isoquinoline-1,3-diones by constructing C-S and C-C bonds in one step.
August 22, 2017: Organic & Biomolecular Chemistry
Xinwei He, Zhiyu Yu, Youpeng Zuo, Cheng Yang, Yongjia Shang
A novel and efficient strategy for the synthesis of 2-hydroxy-6-oxocyclohex-1-enecarboxamides through a Rh2(OAc)4-catalyzed direct carboxamidation of cyclic 2-diazo-1,3-diketones has been developed. The method features readily available starting materials, easy scalability, mild reaction conditions and a simple work-up for product isolation, which makes this strategy highly attractive. A tentative mechanism involving an isocyanide insertion and hydrolysis sequence for this reaction is proposed.
August 22, 2017: Organic & Biomolecular Chemistry
Sam A Spring, Sean Goggins, Christopher G Frost
A novel ferrocene-based substrate for the ratiometric electrochemical detection of β-galactosidase was designed and synthesised. It was demonstrated to be an excellent electrochemical substrate for β-Gal detection with sensitivity as low as 0.1 U mL(-1).
August 22, 2017: Organic & Biomolecular Chemistry
Sankarasekaran Shanmugaraju, Deirdre McAdams, Francesca Pancotti, Chris S Hawes, Emma B Veale, Jonathan A Kitchen, Thorfinnur Gunnlaugsson
We report here a novel one-pot synthetic strategy for the synthesis of a family of N-alkyl-1,8-naphthalimide based Tröger's bases via a nucleophilic substitution reaction of a common 'precursor' (or a 'synthon') N-aryl-1,8-naphthalimide Tröger's base heated at 80 °C in neat aliphatic primary amine, in overall yield of 65-96%. This methodology provides an efficient and one-step facile route to design 1,8-naphthalimide derived Tröger's base structures in analytically pure form without the use of column chromatography purification, that can be used in medicinal chemistry and as supramolecular scaffolds...
August 22, 2017: Organic & Biomolecular Chemistry
Rajender Nallagonda, Reddy Rajasekhar Reddy, Prasanta Ghorai
A palladium-catalyzed oxidation reaction is disclosed where the nitrile functionality on the substrate simply changes the course of the reaction. Our previous finding showed that using the Pd(ii)-catalyst in the presence of benzoquinone as an oxidant, 2-cinnamyl-1,3-dicarbonyls provides functionalized furans via oxidative cyclization. When a nitrile group is replaced with one of the carbonyl functionalities of the same substrate, the oxidative cyclization was completely suppressed; instead, the oxidation at the α,β-position occurred to provide α,β,γ,δ-diene containing β-keto nitriles...
August 21, 2017: Organic & Biomolecular Chemistry
Di Zhu, Wen-Kun Luo, Luo Yang, Da-You Ma
An iodine-catalyzed multiple C-H bond functionalization of isoquinolines with methylarenes via a successive benzylic sp(3) C-H iodination/N-benzylation/amidation/double sp(2) C-H oxidation sequence is developed. This reaction utilizes un-functionalized isoquinolines and readily available methylarenes as starting materials, proceeds under metal-free conditions, and avoids a multi-step experimental operation, to make it an efficient and practical method for the synthesis of N-benzyl isoquinoline-1,3,4-triones...
August 21, 2017: Organic & Biomolecular Chemistry
Claire Beauvineau, Corinne Guetta, Marie-Paule Teulade-Fichou, Florence Mahuteau-Betzer
We report a new turn-off fluorescent probe, PhenDV, for the identification of high affinity quadruplex (G4) DNA ligands. This push-pull fluorophore displays a high fluorescence quantum yield in water (ΦF = 0.21) and is a selective and strong quadruplex DNA binder. We describe its use as a fluorescent indicator for the G4 Fluorescent Intercalator Displacement (FID) assay as its fluorescence is strongly quenched when bound to G4 DNA and fully restored when displaced by ligand. This probe improves the sensitivity of the G4-FID assay, as the read out relies on increased fluorescence instead of quenching observed with classical on/off probes...
August 21, 2017: Organic & Biomolecular Chemistry
Wanzheng Zhang, Yubin Fu, Peirong Qiang, Jens Hunger, Shuai Bi, Wenbei Zhang, Fan Zhang
Initiated by the effective dibromination of syn-BN-heteroacenes, a series of BN-containing conjugated oligomers was successfully synthesized upon transition-metal-catalyzed cross coupling. Their electronic structures can be finely tailored through varying the fused backbone or terminal substituents, endowing them with tunable luminescent properties within blue-violet regions.
August 18, 2017: Organic & Biomolecular Chemistry
Timothy J Vanden Berg, David M Pinkerton, Craig M Williams
The first seco-casbane, EBC-329, isolated from the Australian rainforest, was synthesised from (+)-2-carene in seven steps. This endeavour not only established the absolute stereochemical assignment as (8R,9S)-EBC-329, but also identified, via photoisomerisation, a new seco-casbane family member.
August 18, 2017: Organic & Biomolecular Chemistry
Yousuke Ooyama, Toshiaki Enoki, Satoshi Aoyama, Joji Ohshita
We designed and developed a fused-bibenzo[c]thiophene, namely, 2,9-bis(tert-butyldimethylsilyl)phenanthro[9,8-bc:10,1-b'c']dithiophene (PHDT-Si), as a new π-building block in the emitters, photosensitizers and semiconductors for organic optoelectronic devices. Based on photophysical (photoabsorption, fluorescence and time-resolved fluorescence spectroscopy) and electrochemical measurements (cyclic voltammetry), and density functional theory (DFT) calculations, this work reveals that the fused-bibenzo[c]thiophene PHDT-Si, which is prepared by an efficient synthesis method, has a rigid, high planar and expanded π-conjugation structure, and possesses intense photoabsorption and fluorescence properties (λ = 598 nm (εmax = 41 000 M(-1) cm(-1)) and λ = 613 nm (Φf = 0...
August 18, 2017: Organic & Biomolecular Chemistry
Philippe B Wilson, Ian H Williams
Ring-closure of substituted 2-chlorosuccinates to α- or β-lactones has been studied by means of MP2/6-311+G(d,p)//MP2/6-31+G(d) calculations in water treated as a polarised continuum (PCM) and in vacuum. Optimised geometries have been obtained for 2-chlorosuccinate and its 2-methyl, 3,3-dimethyl, and 2,3,3-trimethyl derivatives, along with the transition structures and products for intramolecular nucleophilic displacement leading to the 3- or 4-membered rings. Relative enthalpies and Gibbs free energies of activation and reaction are presented, along with key geometrical parameters, and changes in electrostatic-potential-derived atomic charges...
August 18, 2017: Organic & Biomolecular Chemistry
Anna Pabis, Nicholas H Williams, Shina C L Kamerlin
Phosphoryl transfer reactions can proceed through several plausible mechanisms, and the potential for both solvent and substrate-assisted pathways (involving proton transfer to the phosphoryl oxygens) complicates both experimental and computational interpretations. To avoid this problem, we have used electronic structure calculations to probe the mechanisms of the reactions of pyridinio-N-phosphonates with pyridine. These compounds avoid the additional complexity introduced by proton transfer between the nucleophile and the leaving group, while also serving as a valuable model for biological P-N cleavage...
August 18, 2017: Organic & Biomolecular Chemistry
Hongxing Jin, Qinglong Zhang, Erqing Li, Penghao Jia, Ning Li, You Huang
A highly enantioselective intramolecular Rauhut-Currier reaction catalyzed by a multifunctional chiral aminophosphine catalyst was reported. A series of hydro-2H-indole derivatives that bear an all-carbon quaternary center were obtained in high yields (up to 94%), and excellent diastereo- and enantioselectivities (up to >20 : 1 dr and >99% ee). And this reaction could be performed on a gram scale using 2 mol% catalyst loading.
August 17, 2017: Organic & Biomolecular Chemistry
Yang Xi, Guohao Zhu, Luning Tang, Shihan Ma, Dongming Zhang, Rong Zhang, Guangke He, Hongjun Zhu
A highly regio- and stereoselective trans-iodofluorination reaction of ynamides with NIS and Et3N·3HF has been achieved, affording (E)-α-fluoro-β-iodoenamides in moderate to good yields. The reaction proceeds under mild reaction conditions and exhibits good functional group compatibility.
August 17, 2017: Organic & Biomolecular Chemistry
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