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Organic & Biomolecular Chemistry

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https://www.readbyqxmd.com/read/28534923/divergent-syntheses-of-iodinated-isobenzofuranones-and-isochromenones-by-iodolactonization-of-2-alkynylbenzoic-acids-in-ionic-liquids
#1
Raffaella Mancuso, Christian C Pomelli, Francesco Malafronte, Asif Maner, Nadia Marino, Cinzia Chiappe, Bartolo Gabriele
The regiochemical outcome of the iodolactonization of 2-alkynylbenzoic acids, carried out at 100 °C in ionic liquids (ILs) as unconventional solvents and with molecular iodine as the iodine source, in the absence of external bases, was found to be strongly dependent on the nature of the IL medium. In particular, while the use of N-ethyl-N-methylmorpholinium dicyanamide (Mor1,2N(CN)2) promoted the stereoselective formation of (E)-3-(iodomethylene)isobenzofuran-1(3H)-ones, through an anti-5-exo-dig cyclization route, the use of 1-ethyl-3-methylimidazolium ethyl sulfate (EmimEtSO4) tended to favor the 6-endo-dig cyclization mode, with preferential or selective formation of 4-iodo-1H-isochromen-1-ones...
May 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28534921/formal-total-synthesis-of-selaginpulvilin-d
#2
Bhavani Shankar Chinta, Beeraiah Baire
An efficient and mild synthetic strategy for the total synthesis of selaginpulvilin D has been reported. A highly chemoselective enyne-alkyne dehydro Diels-Alder reaction has been employed for the construction of the tricyclic fluorene framework present in the natural product selaginpulvilin D. An improved overall yield (10.5%) has been achieved for selaginpulvilin D, starting from commercially available m-anisaldehyde in 9 linear, operationally simple synthetic transformations.
May 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28534920/total-synthesis-of-marine-natural-products-separacenes-a-and-b
#3
Subhendu Das, Rajib Kumar Goswami
A short and convergent route for the stereoselective total synthesis of separacenes A and B has been developed using (+)-methyl d-lactate and d-(-)-tartaric acid as the chiral pools. The characteristic features of this synthesis include the Trost-Rychnovsky alkyne rearrangement to construct the C7-C9 conjugated diene, the Horner-Wadsworth-Emmons olefination to form the C5-C6 and C11-C12 olefins and the Corey-Bakshi-Shibata reaction to install the C-13 hydroxy functionality.
May 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28534905/antimicrobial-peptide-inspired-nh125-analogues-bacterial-and-fungal-biofilm-eradicating-agents-and-rapid-killers-of-mrsa-persisters
#4
Akash Basak, Yasmeen Abouelhassan, Ran Zuo, Hussain Yousaf, Yousong Ding, Robert W Huigens
During microbial infection, antimicrobial peptides are utilized by the immune response to rapidly eradicate microbial pathogens through the destruction of cellular membranes. Inspired by antimicrobial peptides, quaternary ammonium cationic (QAC) compounds have emerged as agents capable of destroying bacterial membranes leading to rapid bacterial death, including the eradication of persistent, surface-attached bacterial biofilms. NH125, an imidazolium cation with a sixteen membered fatty tail, was recently reported to eradicate persister cells and was our starting point for the development of novel antimicrobial agents...
May 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28534902/biosynthetically-inspired-oxidations-of-capillobenzopyranol
#5
Henry P Pepper, Hiu C Lam, Jonathan H George
The synthesis of verrubenzospirolactone from its proposed biosynthetic precursor, capillobenzopyranol, has been shown to be chemically feasible via a simple reaction sequence. The key steps are a chemoselective furan oxidation mediated by NaClO2, a stereoselective dehydration of a γ-methoxybutenolide, and an intramolecular Diels-Alder reaction.
May 23, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28530762/metal-free-i2o5-mediated-direct-construction-of-sulfonamides-from-thiols-and-amines
#6
Minghui Zhu, Wei Wei, Daoshan Yang, Huanhuan Cui, Leilei Wang, Guoqing Meng, Hua Wang
A simple and convenient method has been developed for the construction of sulfonamides via I2O5-mediated sulfonylation of amines with arylthiols. The present protocol provides an attractive approach to sulfonamides in moderate to good yields from readily accessible and easy to handle starting materials under mild and metal-free conditions.
May 22, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28530752/active-metal-template-synthesis-of-a-neutral-indolocarbazole-containing-2-rotaxane-host-system-for-selective-oxoanion-recognition
#7
Asha Brown, Thomas Lang, Kathleen M Mullen, Paul D Beer
An active metal template strategy was used to synthesise a neutral indolocarbazole containing [2]rotaxane anion host system. (1)H NMR anion binding investigations reveal that the [2]rotaxane recognises a range of monoanions in acetone-d5 : D2O 95 : 5 with an unusual interlocked host selectivity for acetate and dihydrogenphosphate oxoanions over halides. The rotaxane displays an overall selectivity for the sulfate dianion, favouring a 2 : 1 host : guest binding stoichiometry at low sulfate concentration and a 1 : 1 stoichiometry in the presence of excess sulfate...
May 22, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28530738/cobalt-carbonyl-catalyzed-carbonylation-of-functionalized-aziridines-to-versatile-%C3%AE-lactam-building-blocks
#8
Nicola Piens, Kristof Van Hecke, Dieter Vogt, Matthias D'hooghe
The Co2(CO)8-catalyzed carbonylation of different classes of non-activated aziridines with diverse substitution patterns was investigated. Special attention was devoted to selectivity issues and reaction optimization. This study resulted in the regio- and stereospecific synthesis of 24 novel β-lactam target structures in high yields on a multigram scale. The synthetic potential of the newly obtained azetidin-2-ones was illustrated via ring-expansion, ring-closure, and/or side chain-functionalization protocols to provide a straightforward entry to novel pyrrolidines, C-fused bi- and tricyclic β-lactams and monocyclic carbapenem analogs...
May 22, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28530734/intramolecular-cascade-rearrangements-of-enynamine-derived-ketenimines-access-to-acyclic-and-cyclic-amidines
#9
Dinesh Pratapsinh Chauhan, Sreejith J Varma, Mahesh Gudem, Nihar Panigrahi, Khushboo Singh, Anirban Hazra, Pinaki Talukdar
Copper-catalyzed reaction of enynamines with sulfonylazides provides acyclic and cyclic amidines. Nucleophilic addition of the tethered amino group on the in situ generated ketenimine forms a six-membered cyclic zwitterionic intermediate which facilitates migration of the tethered amino group to the C5-center giving the acyclic amidine. On the other hand, migration of a substituent on the amino group to C2- and C4-centers results in the formation of cyclic amidines. Computational studies were carried out to validate the mechanism which indicates that the product distribution of the process depends on the substitutions on the enynamine backbone...
May 22, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28524918/urotensin-ii-peptidomimetic-incorporating-a-non-reducible-1-5-triazole-disulfide-bond-reveals-a-pseudo-irreversible-covalent-binding-mechanism-to-the-urotensin-g-protein-coupled-receptor
#10
Salvatore Pacifico, Aidan Kerckhoffs, Andrew J Fallow, Rachel E Foreman, Remo Guerrini, John McDonald, David G Lambert, Andrew G Jamieson
The urotensin-II receptor (UTR) is a class A GPCR that predominantly binds to the pleiotropic cyclic peptide urotensin-II (U-II). U-II is constrained by a disulfide bridge that induces a β-turn structure and binds pseudo-irreversibly to UTR and is believed to result in a structural rearrangement of the receptor. However, it is not well understood how U-II binds pseudo-irreversibly and the nature of the reorganization of the receptor that results in G-protein activation. Here we describe a series of U-II peptidomimetics incorporating a non-reducible disulfide bond structural surrogate to investigate the feasibility that native U-II binds to the G protein-coupled receptor through disulfide bond shuffling as a mechanism of covalent interaction...
May 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28524917/asymmetric-synthesis-of-cf3-containing-tetrahydroquinoline-via-a-thiourea-catalyzed-cascade-reaction
#11
Yuanyuan Zhu, Boyu Li, Cui Wang, Zhenghao Dong, Xiaoling Zhong, Kairong Wang, Wenjin Yan, Rui Wang
An organocatalytic asymmetric method for the synthesis of 2-CF3 tetrahydroquinoline has been achieved. The cascade reaction of 2-aminochalcones with β-CF3 nitroalkenes afforded the products bearing three contiguous stereogenic centers in good yields with excellent diastereoselectivities and enantioselectivities.
May 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28517015/genetic-incorporation-of-4-fluorohistidine-into-peptides-enables-selective-affinity-purification
#12
Christine M Ring, Emil S Iqbal, David E Hacker, Matthew C T Hartman, T Ashton Cropp
Due to the lowered pKa of 4-fluorohistidine relative to histidine, peptides and proteins containing this amino acid are potentially endowed with novel properties. We report here the optimized synthesis of 4-fluorohistidine and show that it can efficiently replace histidine in in vitro translation reactions. Moreover, peptides containing 6×-fluorohistidine tags are able to be selectively captured and eluted from nickel resin in the presence of his-tagged protein mixtures.
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28517012/re-characterization-of-hammerhead-ribozymes-as-molecular-tools-for-intermolecular-rna-cleavage
#13
Getong Liu, Xin Huang, Qinlin Pu, Yongyun Zhao, Feng Du, Juan Dong, Xin Cui, Zhuo Tang
A new guideline for the construction of hammerhead ribozymes to achieve trans-cleavage of a single-stranded RNA molecule was developed. The sequence rule of the HHRz cleavage site was highly recommended to be "DWH" with an optimal binding arm length of 8-9nt, which diverged from the former rule of "NUX".
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28517007/generation-of-a-cell-permeable-cycloheptapeptidyl-inhibitor-against-the-peptidyl-prolyl-isomerase-pin1
#14
Walaa Bedewy, Hui Liao, Nageh A Abou-Taleb, Sherif F Hammad, Tamer Nasr, Dehua Pei
Cyclic peptides are capable of binding and modulating challenging drug targets including protein-protein interactions. However, their lack of membrane permeability prevents their application against intracellular targets. In this study, we show that it is possible to design a cell-permeable and biologically active cycloheptapeptide inhibitor against the intracellular enzyme peptidyl-prolyl isomerase Pin1 by integrating cell-penetrating and target-binding sequences.
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28517004/exploitation-of-new-structurally-diverse-d-glucuronamide-containing-n-glycosyl-compounds-synthesis-and-anticancer-potential
#15
Nuno M Xavier, Alexandre Porcheron, Daniela Batista, Radek Jorda, Eva Řezníčková, Vladimír Kryštof, M Conceição Oliveira
The synthesis and anticancer evaluation of novel N-glycosyl derivatives containing N-substituted glucuronamide moieties, as nucleoside analogs or as prospective mimetics of glycosyl phosphates or of nucleotides, is reported. These compounds comprise N-anomerically-linked nucleobases or motifs that are surrogates of a phosphate group, such as sulfonamide or phosphoramidate moieties. 1-Sulfonamido glucuronamides containing N-benzyl, N-propargyl or N-dodecyl carboxamide units were synthesized through glycosylation of methanesulfonamide with tetra-O-acetyl glucuronamides...
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28516995/regioselective-6-endo-dig-iodocyclization-an-accessible-approach-for-iodo-benzo-a-phenazines
#16
Sonu Kumar, Mohammad Mujahid, Akhilesh K Verma
A facile approach for the synthesis of substituted iodo-benzo[a]phenazines from 2-aryl-3-(aryl/alkylethynyl)quinoxalines via 6-endo-dig ring closure has been described under mild reaction conditions. Iodocyclization proceeds through the iodonium ion intermediate followed by nucleophilic cyclization with the C-H bond of the arene. Furthermore, the resulting 6-iodo-5-aryl/alkyl benzo[a]phenazine derivatives allowed for structural diversification by employing various coupling reactions. The structure of iodo-benzo[a]phenazine was confirmed by X-ray crystallographic studies of the compound...
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28516991/synthesis-properties-and-crystal-structures-of-%C3%AF-extended-double-6-helicenes-contorted-multi-dimensional-stacking-lattice
#17
Takao Fujikawa, Nobuhiko Mitoma, Atsushi Wakamiya, Akinori Saeki, Yasutomo Segawa, Kenichiro Itami
The synthesis and properties of a new π-extended double [6]helicene 2 and a dithia[6]helicene 3 are described. Compared to the previously reported parent double-helicene molecule 1, the introduction of n-butyl groups successfully improved the solubility, which allowed an experimental investigation into the electronic structure of 2 and 3 by photophysical measurements and cyclic voltammetry. The characteristic two-blade propeller structures of 2 and 3 were unambiguously determined by single-crystal X-ray diffraction analysis...
May 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28513756/divergent-synthesis-of-biflavonoids-yields-novel-inhibitors-of-the-aggregation-of-amyloid-%C3%AE-1-42
#18
Tze Han Sum, Tze Jing Sum, Súil Collins, Warren R J D Galloway, David G Twigg, Florian Hollfelder, David R Spring
Biflavonoids are associated with a variety of biologically useful properties. However, synthetic biflavonoids are poorly explored within drug discovery. There is considerable structural diversity possible within this compound class and large regions of potentially biologically relevant biflavonoid chemical space remain untapped or underexplored. Herein, we report the development of a modular and divergent strategy towards biflavonoid derivatives which enabled the step-economical preparation of a structurally diverse collection of novel unnatural biflavonoids...
May 17, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28513753/two-step-conversion-of-carboxylic-esters-into-distally-fluorinated-ketones-via-ring-cleavage-of-cyclopropanol-intermediates-application-of-sulfinate-salts-as-fluoroalkylating-reagents
#19
Yulia A Konik, Marina Kudrjashova, Nele Konrad, Sandra Kaabel, Ivar Järving, Margus Lopp, Dzmitry G Kananovich
Tertiary cyclopropanols easily available from carboxylic esters have been used in the synthesis of distally fluorinated ketones. Cyclopropane ring cleavage reactions in methanol with aqueous tert-butyl hydroperoxide in the presence of a copper(ii) acetate catalyst and sodium triflinate (Langlois reagent) afford β-trifluoromethyl ketones in 16-74% isolated yields. Sodium triflinate serves as a precursor of reactive trifluoromethyl copper species, enabling ring-opening trifluoromethylation, as evidenced by mechanistic studies...
May 17, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28513751/iodine-mediated-synthesis-of-sulfur-bridged-enaminones-and-chromones-via-double-c-sp-2-h-thiolation
#20
Yong Gao, Li Wei, Yunyun Liu, Jie-Ping Wan
The reactions of various enaminones with elemental sulfur giving rise to both sulfur-bridged enaminones and chromones have been realized via iodine promotion. All products were furnished by means of double C(sp(2))-H bond thiolation without using any metal catalyst or sensitive oxidant, providing a simple and efficient protocol for the synthesis of diverse sulfur derivatives of enaminones.
May 17, 2017: Organic & Biomolecular Chemistry
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