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Organic & Biomolecular Chemistry

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https://www.readbyqxmd.com/read/28084490/on-the-nature-of-the-electronic-effect-of-multiple-hydroxyl-groups-in-the-6-membered-ring-the-effects-are-additive-but-steric-hindrance-plays-a-role-too
#1
Christian Marcus Pedersen, Mikael Bols
Research during the last two decades has shown a remarkable directional component of the substituent effects of hydroxy groups, which has a profound effect on the properties of hydroxylated compounds such as carbohydrates. While the epimerisation of a single hydroxyl function is well studied the consequence of multiple epimerisations is more speculative. In this work the effect of three epimerisations was investigated. To this end epimeric 2-phenyl iminoxylitols that have a phenyl group as a conformational anchor and thus hydroxyl groups in the axial or equatorial position, respectively, were synthesized and their pKa and conformation were studied...
January 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28084488/kinetic-enantioselectivity-of-a-protonated-bis-diamido-bridged-basket-resorcin-4-arene-towards-alanine-peptides
#2
C Fraschetti, M Montagna, M E Crestoni, A Calcaterra, F Aiello, L Santi, A Filippi
Efficient enantiodiscrimination of some alanine-containing di- and tri-peptides by using chiral protonated bis(diamido)-bridged basket resorcin[4]arenes depends on several factors, including the basicity of the amino acid residues at the C- and N-termini of the peptide.
January 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28084483/fluorescence-enhancement-of-oligodeoxynucleotides-modified-with-green-fluorescent-protein-chromophore-mimics-upon-triplex-formation
#3
Takashi Kanamori, Akihiro Takamura, Nobuhiro Tago, Yoshiaki Masaki, Akihiro Ohkubo, Mitsuo Sekine, Kohji Seio
Green fluorescent protein (GFP)-based molecular-rotor chromophores were attached to the 5-positions of deoxyuridines, and subsequently, incorporated into the middle positions of oligodeoxynucleotides. These oligonucleotides were designed to form triplex DNA in order to encapsulate the GFP chromophores, mimicking GFP structures. Upon triplex formation, the embedded GFP chromophores exhibited fluorescence enhancement, suggesting the potential application of these fluorescent probes for the detection of nucleic acids...
January 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28084479/chemical-modification-improves-the-stability-of-the-dna-aptamer-gbi-10-and-its-affinity-towards-tenascin-c
#4
Kunfeng Li, Jiali Deng, Hongwei Jin, Xiantao Yang, Xinmeng Fan, Liyu Li, Yi Zhao, Zhu Guan, Yun Wu, Lihe Zhang, Zhenjun Yang
Aptamers are useful tools in molecular imaging due to their numerous attractive properties, such as excellent affinity and selectivity to diverse types of target molecules and biocompatibility. We carried out structure-activity relationship studies with the tenascin-C (TN-C) binding aptamer GBI-10, which is a promising candidate in tumor imaging. To increase the tumor targeting ability and nuclease resistance under physiological conditions, systematic modifications of GBI-10 with single and multiple 2'-deoxyinosine (2'-dI) or d-/l-isonucleoside (d-/l-isoNA) were performed...
January 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074965/n-heterocyclic-carbene-palladium-ii-1-methylimidazole-complex-catalyzed-direct-c-h-bond-arylation-of-imidazo-1-2-a-pyridines-with-aryl-chlorides
#5
Qing-Xian Liu, Bang-Yue He, Peng-Cheng Qian, Li-Xiong Shao
We herein reported the N-heterocyclic carbene-palladium(ii)-1-methylimidazole complex catalyzed direct C-H bond arylation of imidazo[1,2-a]pyridines with aryl chlorides. Under suitable conditions, all reactions between various imidazo[1,2-a]pyridines and aryl chlorides worked well to give the desired C3-H arylated products in acceptable to high yields, giving a convenient and alternative method for the direct C-H bond arylation of imidazo[1,2-a]pyridines, using economic and easily available aryl chlorides as the arylating reagents...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074955/total-synthesis-and-biological-activity-of-dolastatin-16
#6
Loida O Casalme, Arisa Yamauchi, Akinori Sato, Julie G Petitbois, Yasuyuki Nogata, Erina Yoshimura, Tatsufumi Okino, Taiki Umezawa, Fuyuhiko Matsuda
The total synthesis of dolastatin 16, a macrocyclic depsipeptide first isolated from the sea hare Dolabella auricularia as a potential antineoplastic metabolite by Pettit et al., was achieved in a convergent manner. Dolastatin 16 was reported by Tan to exhibit strong antifouling activity, and thus shows promise for inhibiting the attachment of marine benthic organisms such as Amphibalanus amphitrite to ships and submerged artificial structures. Therefore, dolastatin 16 is a potential compound for a new, environmentally friendly antifouling material to replace banned tributyltin-based antifouling paints...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074954/a-highly-selective-fluorescent-probe-for-fe-3-in-living-cells-a-stress-induced-cell-based-model-study
#7
Neetu Sharma, Shahi Imam Reja, Neha Gupta, Vandana Bhalla, Davinder Kaur, Saroj Arora, Manoj Kumar
A rhodamine-phenanthroline dyad based fluorescent probe 4 has been designed and synthesized which selectively monitors Fe(3+) ions among the various metal ions tested. Furthermore, probe 4 has been explored for monitoring of dynamic changes in the Fe(3+) ion level under aggressive Fenton reaction conditions using a cell based model study. More significantly, probe 4 has also been utilized for real time imaging of endogenous Fe(3+) ions in living C6 cell lines, the results of which demonstrated that probe 4 acts as an efficient fluorescent tool for Fe(3+) ion detection in biological systems...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074951/access-to-n-cyanosulfoximines-by-transition-metal-free-iminations-of-sulfoxides
#8
C A Dannenberg, L Fritze, F Krauskopf, C Bolm
A transition metal-free synthesis of N-cyanosulfoximines from sulfoxides using N-chlorosuccinimide (NCS) as oxidising agent and cyanamide as nucleophilic amine source is reported. The products are obtained in moderate to excellent yields. The protocol enables an easy access to N-cyanosulfoximines from readily available starting materials under inversion of configuration at a preexisting stereogenic center.
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074950/self-neutralizing-oligonucleotides-with-enhanced-cellular-uptake
#9
Ivan Yanachkov, Boris Zavizion, Valeri Metelev, Laura J Stevens, Yekaterina Tabatadze, Milka Yanachkova, George Wright, Anna M Krichevsky, David R Tabatadze
There is tremendous potential for oligonucleotide (ON) therapeutics, but low cellular penetration due to their polyanionic nature is a major obstacle. We addressed this problem by developing a new approach for ON charge neutralization in which multiple branched charge-neutralizing sleeves (BCNSs) are attached to the internucleoside phosphates of ON by phosphotriester bonds. The BCNSs are terminated with positively charged amino groups, and are optimized to form ion pairs with the neighboring phosphate groups...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074949/new-compounds-from-a-hydrothermal-vent-crab-associated-fungus-aspergillus-versicolor-xz-4
#10
Chengqian Pan, Yutong Shi, Xuegang Chen, Chen-Tung Arthur Chen, Xinyi Tao, Bin Wu
Three new quinazoline derivatives (1-3), one new oxepin-containing natural product (4) and four new cyclopenin derivatives (5-7 and 9) have been isolated from an EtOAc extract of the Taiwan Kueishantao hydrothermal vent crab-associated fungus Aspergillus versicolor XZ-4. Their planar structures were established by HRMS, 1D and 2D NMR spectroscopic data analyses. The absolute configurations for compounds 1 and 4 were determined by chiral phase HPLC analysis of their hydrolysis products. The absolute configurations of 2, 3 and 7 were defined mainly by comparison of the quantum chemical TDDFT calculated and the experimental ECD spectra, and the absolute configuration of 5 was deduced from comparison of the optical rotation values reported in the literature...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28074946/modulating-the-oxidation-of-cucurbit-n-urils
#11
Jade A McCune, Edina Rosta, Oren A Scherman
The functionalisation of cucurbit[n]uril macrocycles carried out through an oxidative approach in water using ammonium persulfate was studied. Through complexation with a doubly-charged bisimidazolium guest we were able to detect, distinguish and quantify the presence of each CB[n]-(OH)x (where 1 ≤ x ≤ 2n) derivative for the first time. The impact of oxidation on each CB[n] (n = 6-8) was studied individually, as well as in the presence of other competing CB[n] species. We were able to understand the reactivity of the parent CB[n] alongside its hydroxylated derivatives, CB[n]-(OH)x, and show that the oxidation of CB[n] through a free-radical approach cannot result in stoichiometric hydroxylation despite previous literature reports by Bardelang, Ouari and co-workers, J...
January 11, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28071780/correction-%C3%AE-amyrin-synthase-from-euphorbia-tirucalli-l-functional-analyses-of-the-highly-conserved-aromatic-residues-phe413-tyr259-and-trp257-disclose-the-importance-of-the-appropriate-steric-bulk-and-cation-%C3%AF-and-ch-%C3%AF-interactions-for-the-efficient-catalytic
#12
Ryousuke Ito, Chika Nakada, Tsutomu Hoshino
Correction for 'β-Amyrin synthase from Euphorbia tirucalli L. functional analyses of the highly conserved aromatic residues Phe413, Tyr259 and Trp257 disclose the importance of the appropriate steric bulk, and cation-π and CH-π interactions for the efficient catalytic action of the polyolefin cyclization cascade' by Ryousuke Ito et al., Org. Biomol. Chem., 2017, 15, 177-188.
January 10, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28071775/copper-catalyzed-c-o-bond-cleavage-and-cyclization-synthesis-of-indazolo-3-2-b-quinazolinones
#13
Rui Qiao, Leping Ye, Kun Hu, Shuling Yu, Weiguang Yang, Miaochang Liu, Jiuxi Chen, Jinchang Ding, Huayue Wu
The first example of a copper-catalyzed halogen-free protocol to construct indazolo[3,2-b]quinazolinones was developed through sequential inert C-O bond cleavage followed by intramolecular C-N bond formation. This protocol represents an efficient synthetic tool for accessing a more diverse range of functionalized indazolo[3,2-b]quinazolinones. The structure of the newly synthesized indazolo[3,2-b]quinazolinones was unambiguously confirmed by X-ray crystal diffraction analysis.
January 10, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28067392/oxidative-coupling-of-1-2-methyl-4-phenylquinolin-3-yl-ethanone-with-ethanol-and-unexpected-deacetylative-synthesis-of-3-hydroxy-quinoline
#14
Parul Chauhan, Makthala Ravi, Ruchir Kant, Prem P Yadav
An efficient one pot method for the synthesis of anti-α,β-epoxy ketones from 1-(2-methyl-4-phenylquinolin-3-yl)ethanone and ethanol has been developed by a modified Darzen reaction. The reaction occurs under oxidative conditions via a cascade sequence of bromination, aldol condensation followed by substitution. The reaction in the presence of NBS and a base however, in the absence of an oxidant, led to the formation of the corresponding 3-hydroxylated product via an unusual rearrangement.
January 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28067389/nhc-catalyzed-4-2-annulation-of-2-bromo-2-enals-with-acylhydrazones-enantioselective-synthesis-of-%C3%AE-lactams
#15
Baomin Sun, Lijiu Gao, Shide Shen, Chenxia Yu, Tuanjie Li, Yuanwei Xie, Changsheng Yao
An asymmetric assembly of δ-lactams was realized via the NHC-catalyzed formal [4 + 2] annulation of acylhydrazones and 2-bromo-2-enals bearing γ-H. The advantages of this protocol include high enantioselectivity, good yields, mild reaction conditions and potential biological significance of the final products.
January 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28067385/a-dbu-catalyzed-michael-pinner-isomerization-cascade-reaction-of-3-hydroxyoxindoles-with-isatylidene-malononitriles-access-to-highly-functionalized-bispirooxindoles-containing-a-fully-substituted-dihydrofuran-motif
#16
Yan-Shuo Zhu, Wen-Bo Wang, Bei-Bei Yuan, Ya-Ning Li, Qi-Lin Wang, Zhan-Wei Bu
The first DBU-catalyzed Michael/Pinner/isomerization cascade reaction of 3-hydrooxindoles with isatylidene malononitriles was developed, and the corresponding highly functionalized bispirooxindoles containing a fully substituted dihydrofuran motif were obtained in up to 92% yields. This protocol also provides an efficient method for the synthesis of an α-cyano-γ-butyrolactone bispirooxindole. In addition, a one-pot three-component cascade reaction was conducted. Also, the asymmetric version of the cascade reaction was achieved...
January 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28066847/an-efficient-ugi-3cr-aza-diels-alder-pomeranz-fritsch-protocol-towards-novel-aza-analogues-of-%C3%A2-nuevamine-%C3%A2-lennoxamine-and-magallanesine-a-diversity-oriented-synthesis-approach
#17
Óscar Vázquez-Vera, Jorge S Sánchez-Badillo, Alejandro Islas-Jácome, Manuel A Rentería-Gómez, Shrikant G Pharande, Carlos J Cortes-García, Mónica A Rincón-Guevara, Ilich A Ibarra, Rocío Gámez-Montaño, Eduardo González-Zamora
A rapid and efficient synthesis of a series of (±)-nuevamine, (±)-lennoxamine and magallanesine aza analogues is described. The synthetic strategy involves Ugi-3CR and two further condensation processes, aza-Diels-Alder cycloaddition and the Pomeranz-Fritsch reaction. The variation of the chain-size in aldehyde moieties provided structural diversity in only two operational reaction steps.
January 9, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28059419/a-mitochondria-targeting-fluorescent-probe-for-the-selective-detection-of-glutathione-in-living-cells
#18
Xue-Liang Liu, Li-Ya Niu, Yu-Zhe Chen, Mei-Ling Zheng, Yunxu Yang, Qing-Zheng Yang
We report a fluorescent probe for the selective detection of mitochondrial glutathione (GSH). The probe, containing triphenylphosphine as a mitochondrial targeting group, exhibited ratiometric and selective detection of GSH over Cys/Hcy. The probe was used for imaging mitochondrial GSH in living HeLa cells.
January 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28059413/convenient-synthesis-of-6-alkyl-phenanthridines-and-1-alkyl-isoquinolines-via-silver-catalyzed-oxidative-radical-decarboxylation
#19
Qian Yao, Xin Zhou, Xiuli Zhang, Cong Wang, Peng Wang, Ming Li
A convenient and efficient protocol for the synthesis of 6-alkyl phenanthridines and 1-alkyl isoquinolines has been developed. The reaction relies on the coupling of 2-isocyanobiphenyls and vinyl isonitriles with alkyl radicals formed by the silver-catalyzed decarboxylation of stoichiometric aliphatic carboxylic acids, and affords diverse phenanthridine and isoquinoline derivatives under mild reaction conditions. The experiment of β-scission of cyclobutylcarbinyl radicals is used to shed light on the reaction mechanism...
January 6, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28059412/stepwise-cyclopropanation-on-the-polycyclopropanated-polyketide-formation-in-jawsamycin-biosynthesis
#20
Tomoshige Hiratsuka, Hideaki Suzuki, Atsushi Minami, Hideaki Oikawa
Jawsamycin is a polyketide-nucleoside hybrid with a unique polycyclopropane moiety on a single polyketide chain. The unexpected isolation of cyclopropane deficient jawsamycin analogs allowed us to propose a stepwise cyclopropanation mechanism for the enzymatic synthesis of this polyketide. The concise timing of the cyclopropanation could be regulated by a delicate balance between reaction rates of the condensation and cyclopropanation reactions.
January 6, 2017: Organic & Biomolecular Chemistry
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