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Organic & Biomolecular Chemistry

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https://www.readbyqxmd.com/read/29218345/a-coelenterazine-type-bioluminescent-probe-for-nitroreductase-imaging
#1
Xingye Yang, Zhenzhen Li, Tianyu Jiang, Lupei Du, Minyong Li
Novel coelenterazine-type bioluminescent probes have been designed and synthesized to detect nitroreductase (NTR) in hypoxic tumors. The design strategy is that NTR catalyzes the reduction of the nitrobenzyl moiety to the aniline group with an electron donor, thus resulting in 1,4 or 1,6-rearrangement-elimination to release coelenterazine analogues, which can be catalyzed by Renilla luciferase to emit bioluminescence. After careful evaluation, almost all probes had a 3-fold greater response for NTR over other biologically relevant substances at >100-fold dose more than NTR...
December 8, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29218339/aerobic-oxidative-acylation-of-nitroarenes-with-arylacetic-esters-under-mild-conditions-facile-access-to-diarylketones
#2
Jiang-Sheng Li, Qian Yang, Fan Yang, Guo-Qin Chen, Zhi-Wei Li, Yin-Jie Kuang, Wei-Jing Zhang, Peng-Mian Huang
A facile and regioselective base-mediated aerobic oxidative acylation of nitroarenes to access diarylketones under mild conditions has been developed. It features the use of bench-stable and readily available arylacetates as acyl surrogates, and the absence of transition-metals and synthetic oxidants. This protocol involves a cascade CDC/oxidative decarboxylation process.
December 8, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29215122/diarylmaleimide-based-branched-oligomers-strong-full-color-emission-in-both-solution-and-solid-films
#3
Jingwei Wang, Rong Zheng, Huan Chen, Huimei Yao, Liyu Yan, Jie Wei, Zhenghuan Lin, Qidan Ling
Maleimide and benzene are employed as a dendron and a core, respectively, to construct two series of non-conjugate branched oligomers (B3G1 and B1G2) based on diarylmaleimide fluorophores by an alkylation reaction. Surface aryl groups are changed to tune the emissive color of branched oligomers from blue (λem = 480 nm) to red (λem = 651 nm), realizing full-color emission. The investigation on the photophysical properties of the oligomers indicates that they display intense emission in both solution and solid films, due to the suppression of intramolecular rotation and intermolecular interaction...
December 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29215120/searching-for-avidity-by-chemical-ligation-of-combinatorially-self-assembled-dna-encoded-ligand-libraries
#4
Stefan Matysiak, Klaus Hellmuth, Afaf H El-Sagheer, Arun Shivalingam, Yavuz Ariyurek, Marco de Jong, Martine J Hollestelle, Ruud Out, Tom Brown
DNA encoded ligands are self-assembled into bivalent complexes and chemically ligated to link their identities. To demonstrate their potential as a combinatorial screening platform for avidity interactions, the optimal bivalent aptamer design (examplar ligands) for human alpha-thrombin is determined in a single round of selection and the DNA scaffold replaced with minimal impact on the final design.
December 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29214248/rh-iii-catalyzed-ortho-c-h-alkynylation-of-n-phenoxyacetamides-with-hypervalent-iodine-alkyne-reagents-at-room-temperature
#5
Sisheng Hu, Liang Lu, Tongyang Zhu, Qian Wu, Ying Chen, Jie Jack Li, Jing Zhao
A Rh(iii)-catalyzed C-H alkynylation of substituted N-phenoxyacetamides has been developed with the aid of hypervalent iodine-alkyne reagents. Complementary to the Sonogashira coupling reaction, this protocol provides an efficient and straightforward method to access aryl alkynes at room temperature. The multifunctional directing group is preserved which can be further employed for ortho-directed functionalizations to obtain additional new complex products.
December 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210431/scandium-as-a-pre-catalyst-for-the-deoxygenative-allylation-of-benzylic-alcohols
#6
Ivan Šolić, Pattarakiat Seankongsuk, Joanna Kejun Loh, Tirayut Vilaivan, Roderick W Bates
Scandium triflate is an effective pre-catalyst for the deoxygenative allylation of benzylic alcohols with a narrow substrate window. The reaction is shown to proceed through a "hidden Brønsted acid" mechanism. The reaction is efficient provided that the aryl group is neither too electron rich nor too electron poor. It is shown that this allows useful selectivity. The reaction also works for benzyhydryl alcohols with broader scope. The reaction may also be catalysed by Nafion.
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210421/cyclic-azole-homologated-peptides-from-marine-sponges
#7
REVIEW
Tadeusz F Molinski
This review discusses the chemistry of cyclic azole-homologated peptides (AHPs) from the marine sponges, Theonella swinhoei, other Theonella species, Calyx spp. and Plakina jamaicensis. The origin, distribution of AHPs and molecular structure elucidations of AHPs are described followed by their biosynthesis, bioactivity, and synthetic efforts towards their total synthesis. Reports of partial and total synthesis of AHPs extend beyond peptide coupling reactions and include creative construction of the non-proteinogenic amino acid components, mainly the homologated heteroaromatic and α-keto-β-amino acids...
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210420/a-novel-approach-to-5h-pyrazino-2-3-b-indoles-via-annulation-of-3-diazoindolin-2-imines-with-2h-azirines-or-5-alkoxyisoxazoles-under-rh-ii-catalysis
#8
Julia O Ruvinskaya, Nikolai V Rostovskii, Ilya P Filippov, Alexander F Khlebnikov, Mikhail S Novikov
A novel one-step method for the preparation of 5H-pyrazino[2,3-b]indoles with different substitution patterns in all rings of the tricyclic system via the Rh2(OAc)4-catalyzed reaction of 2H-azirines with 3-diazoindolin-2-imines is reported. Alkyl 5H-pyrazino[2,3-b]indole-3-carboxylates were also prepared by a one-pot procedure from synthetic equivalents of alkyl 2H-azirine-2-carboxylates, 5-alkoxyisoxazoles. The reactions provide the first examples of the use of Rh(ii) catalysis for intermolecular annulations with 2H-azirines and isoxazoles...
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210415/synthesis-of-polysubstituted-pyridines-from-oxime-acetates-using-nh4i-as-a-dual-function-promoter
#9
Yujia Xia, Jinhui Cai, Huawen Huang, Guo-Jun Deng
Pyridine formation with oxime acetates as the building blocks under metal-free conditions is described. Ammonium iodide has proved to be a highly efficient promoter for oxime N-O bond reduction and subsequent condensation reactions, whereby it played a dual-function role in the transformation. While the three-component reaction of oxime acetates, benzaldehydes, and 1,3-dicarbonyls proceeded well with the assistance of a stoichiometric amount of ammonium iodide, the condensation of oximes and acroleins was enabled by using a catalytic initiator to afford substituted pyridines...
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210413/design-synthesis-and-conformational-analysis-of-3-cyclo-butylcarbamoyl-hydantoins-as-novel-hydrogen-bond-driven-universal-peptidomimetics
#10
M C Bellucci, M Frigerio, C Castellano, F Meneghetti, A Sacchetti, A Volonterio
A collection of systematically substituted 3-cyclo-butylcarbamoyl hydantoins was synthesized by a regioselective multicomponent domino process followed by easy coupling reactions. Calculations, NMR studies and X-ray analysis show that these scaffolds are able to project their side chains similar to common secondary structures, such as the α-helix and β-turn, with favourable enthalpic and entropic profiles.
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29210409/narcissistic-chiral-self-sorting-of-molecular-face-rotating-polyhedra
#11
Xinchang Wang, Pixian Peng, Wei Xuan, Yu Wang, Yongbin Zhuang, Zhongqun Tian, Xiaoyu Cao
Narcissistic chiral self-sorting prevailed in the assembly of molecular face-rotating polyhedra from a C3h building block 5,5,10,10,15,15-hexabutyl-truxene-2,7,12-tricarbaldehyde and racemic mixtures of 1,2-diamines. Out of 124 possible stereoisomers, a pair of racemic polyhedra dominated, wherein (1R,2R)-diamines were segregated in AAAA polyhedra and (1S,2S)-diamines in CCCC polyhedra. This chiral self-sorting process is regulated by facial non-covalent interactions in the polyhedra. In contrast, D3h facial building blocks 1,3,5-tris-(4-formyl-phenyl)triazine and racemic mixtures of 1,2-diamines assembled into polyhedra without facial interactions, and their assembly process did not undergo apparent chiral self-sorting...
December 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29199738/metal-free-electrophilic-phosphination-of-electron-rich-arenes-arenols-and-aromatic-thiols-with-diarylphosphine-oxides
#12
Tao Yuan, Shenlin Huang, Chun Cai, Guo-Ping Lu
A new protocol for achieving the phosphination of arenes, arenols and thiols has been disclosed. This chemistry, in which diaryl(((trifluoromethyl)sulfonyl)oxy)phosphines as a kind of electrophilic phosphination reagents are in situ generated from diarylphosphine oxides, provides an efficient and mild approach for the synthesis of aromatic organophosphorus compounds.
December 4, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29199735/ligand-free-palladacycle-facilitated-suzuki-coupling-of-hindered-2-arylbenzothiazole-derivatives-yields-potent-and-selective-cox-2-inhibitors
#13
Mohamed S A Elsayed, Siran Chang, Mark Cushman
A similarity search and molecular modeling study suggested the 2'-aryl-2-arylbenzothiazole framework as a novel scaffold for the design of COX-2-selective inhibitors. Conventional Suzuki coupling conditions did not furnish the designed compounds in good yield from 2'-bromo-2-arylbenzothiazole as the starting material. A novel ligand-free Suzuki-Miyaura coupling methodology was developed for sterically hindered 2'-bromo-2-arylbenzothiazoles. The reaction depends on the coordination properties of the benzothiazole ring nitrogen, which is involved in the formation of a palladacyclic intermediate that was synthesized independently and converted to the final product...
December 4, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29199315/negishi-cross-couplings-in-the-synthesis-of-amino-acids
#14
REVIEW
William D G Brittain, Steven L Cobb
The Negishi cross-coupling is a powerful C-C bond-forming reaction widely utilised in many areas of organic synthesis. This review details the use of Negishi cross-couplings in the synthesis of unnatural amino acids. The application of this reaction in the preparation of aromatic, heteroaromatic, and, complex amino acid derivatives are reviewed and presented herein.
December 4, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29192928/synthesis-of-2-methylbenzoxazoles-directly-from-n-phenylacetamides-catalyzed-by-palladium-acetate
#15
Biying Wang, Chengfei Jiang, Jiasheng Qian, Shuwei Zhang, Xiaodong Jia, Yu Yuan
A method to synthesize 2-methylbenzoxazoles directly from N-phenylacetamides catalyzed by Pd(OAc)2 in the presence of K2S2O8 and TfOH has been developed. The desired products were obtained in moderate to excellent yields. This approach provides a facile procedure to prepare benzoxazoles with available substrates. It is found that TfOH is the key factor for this cyclization reaction. A plausible mechanism of the reaction is proposed according to the control reactions and the literature.
December 1, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29192703/the-direct-and-highly-diastereoselective-synthesis-of-3-4-epoxy-2-piperidones-application-to-the-total-synthesis-and-absolute-configurational-assignment-of-3%C3%AE-4%C3%AE-epoxy-5%C3%AE-pipermethystine
#16
Urbano Osorio-Nieto, Laura Y Vázquez-Amaya, Herbert Höpfl, Leticia Quintero, Fernando Sartillo-Piscil
The substrate-controlled asymmetric total synthesis and absolute configurational assignment of biologically active 3α,4α-epoxy-5β-pipermethystine, a minor component in the aerial parts of kava, has been achieved by featuring, as a key step, the environmentally friendly and direct synthesis of 2,3-epoxyamides from allyl amines. By using the chiron approach, first a carbohydrate-derived dehydropiperidine was prepared and subjected to a stereoselective tandem C-H/C[double bond, length as m-dash]C oxidation reaction...
December 1, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29192699/design-and-synthesis-of-a-hybrid-framework-of-indanone-and-chromane-total-synthesis-of-a-homoisoflavanoid-brazilane
#17
Jinwoo Kim, Ikyon Kim
A chemical backbone of tetracyclic homoisoflavanoid natural products such as brazilin inspired us to design a new chemical scaffold, 6a,11b-dihydroindeno[2,1-c]chromen-7(6H)-one, which is a hybrid structure of indanone and chromane. Pd-catalyzed Suzuki-Miyaura cross-coupling of 4-chloro-2H-chromene-3-carbaldehydes with (hetero)aryl boronic acids was employed as a means to introduce a wide variety of (hetero)aryl groups as the D ring and intramolecular Friedel-Crafts acylation was utilized to construct the C ring of this skeleton...
December 1, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29188248/pd-catalyzed-one-pot-sequential-cross-coupling-reactions-of-tetrabromothiophene
#18
Kapil Mohan Saini, Rakesh K Saunthwal, Akhilesh K Verma
Unsymmetrical one-pot sequential cross-coupling reactions of sterically hindered tetrabromothiophene with arylboronic acid and an alkyne/alkene to afford selective bi-, tri-, and tetrasubstituted aryl/alkynyl-thiophenes with the aid of a palladium catalyst were described. The reaction proceeds via a site-selective Suzuki/Sonogashira coupling, followed by selective Sonogashira, Suzuki and Heck coupling reactions. This methodology has demonstrated an important framework for the synthesis of organic scaffolds.
November 30, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29188244/nitrilium-ions-synthesis-and-applications
#19
REVIEW
Tom van Dijk, J Chris Slootweg, Koop Lammertsma
Nitrilium ions have been well-established in organic chemistry for many decades, but recent developments show them to be far more versatile than hitherto recognized. They are known as stable salts, can be generated in situ, or are present as transient intermediates. We provide a succinct, but comprehensive review on the synthesis, stability, and reactivity of nitrilium ions as synthons for imines, their use in the synthesis of a large spectrum of heterocycles, and their reactions with transition metal complexes...
November 30, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29186227/-snorkelling-vs-diving-in-mixed-micelles-probed-by-means-of-a-molecular-bathymeter
#20
Gemma M Rodriguez-Muñiz, Miguel Gomez-Mendoza, Edurne Nuin, Inmaculada Andreu, M Luisa Marin, Miguel A Miranda
A photoactive bathymeter based on a carboxylic acid moiety covalently linked to a signalling methoxynaphthalene (MNP) fluorophore has been designed to prove the concept of "snorkelling" vs. "diving" in mixed micelles (MM). The carboxylic acid "floats" on the MM surface, while the MNP unit sinks deep in MM. The rate constants of MNP fluorescence quenching by iodide, which remains basically in water, consistently decrease with increasing spacer length, revealing different regions. This is associated with the distance MNP should "dive" in MM to achieve protection from aqueous reactants...
November 29, 2017: Organic & Biomolecular Chemistry
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