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Organic & Biomolecular Chemistry

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https://www.readbyqxmd.com/read/28436530/solvent-free-uncatalyzed-asymmetric-ene-reactions-of-n-tert-butylsulfinyl-3-3-3-trifluoroacetaldimines-a-general-approach-to-enantiomerically-pure-%C3%AE-trifluoromethyl-tryptamines
#1
Giuseppe Mazzeo, Giovanna Longhi, Sergio Abbate, Martina Palomba, Luana Bagnoli, Francesca Marini, Claudio Santi, Jianlin Han, Vadim A Soloshonok, Emilio Di Crescenzo, Renzo Ruzziconi
A novel approach to regioselectively substituted and stereoselectively α-trifluoromethylated tryptamines is reported based on the ene reaction of Boc-protected 3-methyleneindolines with optically pure (R)- or (S)-tert-butanesulfinyltrifluoroacetaldimine. Boc- and sulfinylamido-protected α-trifluoromethyltryptamines are obtained in 60-70% yield and 85/15 dr by just heating equimolar amounts of the two reaction partners at 80-90 °C for 2-3 h without a solvent. The absolute configuration of the amino α-carbon has been assigned based on the vibrational circular dichroism (VCD) spectral analysis...
April 24, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28436528/a-highly-selective-and-sensitive-fluorescent-probe-for-cu-2-based-on-a-novel-naphthalimide-rhodamine-platform-and-its-application-in-live-cell-imaging
#2
Chang Liu, Xiaojie Jiao, Song He, Liancheng Zhao, Xianshun Zeng
Copper plays important roles in a variety of fundamental physiological processes. At the cell organelle level, aberrant copper homeostasis in lysosomes can lead to various serious diseases. Herein, a bifluorophore-based, lysosome-targetable Cu(2+)-selective ratiometric fluorescent probe (V) has been synthesized by reasonable design. The probe V shows high selectivity toward Cu(2+) ions over other cations and exhibits high sensitivity (1.45 nM) for the detection of Cu(2+) ions. Meanwhile, the probe is cell permeable and suitable for ratiometric visualization of lysosomal Cu(2+) in the living cell...
April 24, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28436523/mechanistic-insights-into-the-selective-cyclization-of-indolines-with-alkynes-and-alkenes-to-produce-six-and-seven-membered-1-7-fused-indolines-via-rh-iii-catalysis-a-theoretical-study
#3
Lingli Han, Xinyu Zhang, Xingdong Wang, Fengyue Zhao, Shaojing Liu, Tao Liu
The coupling reaction mechanisms of the Rh(iii)-catalyzed redox-neutral C7-selective aryl C-H functionalization of indolines with alkynes and alkenes have been theoretically investigated with the aid of the density functional theory (DFT) calculations. Our calculation results indicate that the active catalyst in this system is the cationic species [Cp*Rh(OAc)](+) (2cat) instead of the neutral species Cp*Rh(OAc)2 (1cat). The origin of forming different products associated with using different coupling partners was also rationalized in detail...
April 24, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28436515/exploring-the-reversal-of-enantioselectivity-on-a-zinc-dependent-alcohol-dehydrogenase
#4
Miguel A Maria-Solano, Adrian Romero-Rivera, Sílvia Osuna
Alcohol Dehydrogenase (ADH) enzymes catalyse the reversible reduction of prochiral ketones to the corresponding alcohols. These enzymes present two differently shaped active site pockets, which dictate their substrate scope and selectivity. In this study, we computationally evaluate the effect of two commonly reported active site mutations (I86A, and W110T) on a secondary alcohol dehydrogenase from Thermoanaerobacter brockii (TbSADH) through Molecular Dynamics simulations. Our results indicate that the introduced mutations induce dramatic changes in the shape of the active site, but most importantly they impact the substrate-enzyme interactions...
April 24, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28430269/an-active-catalytic-system-for-suzuki-miyaura-cross-coupling-reactions-using-low-levels-of-palladium-loading
#5
Meng-Qi Yan, Jia Yuan, Fang Lan, Si-Hao Zeng, Meng-Yue Gao, Sheng-Hua Liu, Jian Chen, Guang-Ao Yu
An easily available Pd(OAc)2/(2-(anthracen-9-yl)-1H-inden-3-yl) dicyclohexylphosphine/toluene/(i)PrOH/water catalytic system was developed, which shows high catalytic activity in the Suzuki-Miyaura cross-coupling reactions of a diverse array of aryl and heteroaryl chlorides with Pd loadings down to 0.01 mol%.
April 21, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426086/circularly-polarised-luminescence-of-pyrenyl-di-and-tri-peptides-with-mixed-d-and-l-amino-acid-residues
#6
Yuki Mimura, Tomoki Nishikawa, Ryo Fuchino, Shiho Nakai, Nobuo Tajima, Mizuki Kitamatsu, Michiya Fujiki, Yoshitane Imai
Multiple pyrenes as pendants of enantioimpure di-/tripeptides (abbreviated as N-LD-C, N-DL-C, N-LLD-C and N-DDL-C) showed pyrene-origin CPL and CD signals, which were associated with conflicting CPL-/CD-signs, compared to the corresponding enantiopure di-/tri-peptides.
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426085/n-heterocyclic-carbene-catalyzed-stereoselective-construction-of-olefinic-carbon-sulfur-bonds-via-cross-coupling-reaction-of-gem-difluoroalkenes-and-thiols
#7
Zi-Song Cong, Yang-Guo Li, Lei Chen, Fen Xing, Guang-Fen Du, Cheng-Zhi Gu, Lin He
A novel organocatalytic olefinic carbon-sulfur bond forming reaction was developed. Under the catalysis of 10 mol% stable N-heterocyclic carbene, thiols undergo direct nucleophilic substitution reaction with gem-difluoroalkenes to produce α-fluorovinyl thioethers in high yields with excellent Z-selectivity. In this process, bases are not necessary.
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426084/synthesis-of-2-amino-and-2-arylazoazulenes-via-nucleophilic-aromatic-substitution-of-2-chloroazulenes-with-amines-and-arylhydrazines
#8
Taku Shoji, Shuhei Sugiyama, Takanori Araki, Akira Ohta, Ryuta Sekiguchi, Shunji Ito, Shigeki Mori, Tetsuo Okujima, Masafumi Yasunami
The SNAr reaction of 2-chloroazulene derivative 1 with ethoxycarbonyl groups at the 1,3-positions of the azulene ring with several amines afforded the corresponding 2-aminoazulenes 3-9 in excellent yields. 2-Chloroazulene (2) without the electron-withdrawing groups reacted with highly nucleophilic cyclic amines (i.e., morpholine, piperidine and pyrrolidine) under the high-temperature conditions in a sealed tube to produce the corresponding 2-aminoazulenes 10-12 in good yields. 2-Aminoazulenes 10-14 without the electron-withdrawing groups were also obtained in good yields by the treatment of compounds 3-7 with 100% H3PO4, but in the cases of the reaction of 8 and 9 with a secondary amine function, the decomposition of the products resulted...
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426066/correction-metal-and-additive-free-oxygen-atom-transfer-reaction-an-efficient-and-chemoselective-oxidation-of-sulfides-to-sulfoxides-with-cyclic-diacyl-peroxides
#9
Shaoyan Gan, Junjie Yin, Yuan Yao, Yang Liu, Denghu Chang, Dan Zhu, Lei Shi
Correction for 'Metal- and additive-free oxygen-atom transfer reaction: an efficient and chemoselective oxidation of sulfides to sulfoxides with cyclic diacyl peroxides' by Shaoyan Gan et al., Org. Biomol. Chem., 2017, 15, 2647-2654.
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426047/selective-construction-of-quaternary-stereocentres-in-radical-cyclisation-cascades-triggered-by-electron-transfer-reduction-of-amide-type-carbonyls
#10
Huan-Ming Huang, Pablo Bonilla, David J Procter
Radical-radical cyclisation cascades, triggered by single-electron-transfer to amide-type carbonyls using SmI2-H2O-LiBr, result in the selective construction of quaternary carbon stereocentres. The cascades deliver tricyclic barbiturates with four stereocentres in good yield and with excellent diastereocontrol.
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28426046/multicomponent-reaction-through-cooperative-trio-catalysis-incorporating-enamine-br%C3%A3-nsted-acid-and-metal-lewis-acid-catalysis-a-concise-route-to-access-chromans
#11
Chamini V Karunaratne, Ryan G Sarkisian, Jennifer Reeves, Yongming Deng, Kraig A Wheeler, Hong Wang
An atom-economical multicomponent cascade reaction of salicylaldehydes, cyclohexanones and arylamines has been developed for the synthesis of three-ring fused chromans. This reaction was achieved through cooperative enamine-metal Lewis acid assisted Brønsted acid catalysis, furnishing the products in excellent yields with good diastereoselectivity.
April 20, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422263/synthesis-of-oxazolidinones-rhodium-catalyzed-c-h-amination-of-n-mesyloxycarbamates
#12
Hélène Lebel, Laura Mamani Laparra, Maroua Khalifa, Carl Trudel, Clément Audubert, Mathieu Szponarski, Cédric Dicaire Leduc, Emna Azek, Matthias Ernzerhof
N-Mesyloxycarbamates undergo intramolecular C-H amination reactions to afford oxazolidinones in good to excellent yields in the presence of rhodium(ii) carboxylate catalysts. The reaction is performed under green conditions and potassium carbonate is used, forming biodegradable potassium mesylate as a reaction by-product. This method enables the production of electron-rich, electron-deficient, aromatic and heteroaromatic oxazolidinones in good to excellent yields. Conformationally restricted cyclic secondary N-mesyloxycarbamates furnish cis-oxazolidinones in high yields and selectivity; DFT calculations are provided to account for the observed selectivity...
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422262/rifamorpholines-a-e-potential-antibiotics-from-locust-associated-actinobacteria-amycolatopsis-sp-hca4
#13
Yong Sheng Xiao, Bo Zhang, Mei Zhang, Zhi Kai Guo, Xin Zhao Deng, Jing Shi, Wei Li, Rui Hua Jiao, Ren Xiang Tan, Hui Ming Ge
Cultivation of locust associated rare actinobacteria, Amycolatopsis sp. HCa4, has provided five unusual macrolactams rifamorpholines A-E. Their structures were determined by interpretation of spectroscopic and crystallographic data. Rifamorpholines A-E possess an unprecedented 5/6/6/6 ring chromophore, representing a new subclass of rifamycin antibiotics. The biosynthetic pathway for compounds 1-5 involves a key 1,6-cyclization for the formation of the morpholine ring. Compounds 2 and 4 showed potent activities against methicillin-resistant Staphylococcus aureus (MRSA) with MICs of 4...
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422258/catalyst-free-synthesis-of-novel-dimeric-%C3%AE-carboline-derivatives-via-an-unexpected-2-2-2-annulation
#14
Hai-Lei Cui, Jing-Fang Wang, Hai-Lin Zhou, Xiao-Lin You, Xiao-Jie Jiang
We report here an unexpected catalyst-free [2 + 2 + 2] annulation reaction which allows access to novel complex dimeric β-carboline derivatives in a single step. Various substituted ynones could react with dihydro-β-carboline imines to deliver interesting [2 + 2 + 2] annulation products in moderate to good yields. Alkynoates can also be tolerated in this system.
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422251/-anti-michael-addition-of-grignard-reagents-to-sulfonylacetylenes-synthesis-of-alkynes
#15
Francisco Esteban, Lazhar Boughani, José L García Ruano, Alberto Fraile, José Alemán
In this work, the addition of Grignard reagents to arylsulfonylacetylenes, which undergoes an "anti-Michael addition", resulting in their alkynylation under very mild conditions is described. The simplicity of the experimental procedure and the functional group tolerance are the main features of this methodology. This is an important advantage over the use of organolithium at -78 °C that we previously reported. Moreover, the synthesis of diynes and other examples showing functional group tolerance in this anti-Michael reaction is also presented...
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422248/umpolung-of-protons-from-h2o-a-metal-free-chemoselective-reduction-of-carbonyl-compounds-via-b2pin2-h2o-systems
#16
Qingqing Xuan, Cong Zhao, Qiuling Song
H2O is routinely described as a proton donor, however, in the presence of diboron compounds, the umpolung reaction of H2O under metal-free conditions was successfully developed, which could afford hydride species, leading to a highly efficient and chemoselective reduction of C[double bond, length as m-dash]O bonds. This strategy exhibits excellent chemoselectivities toward carbonyl groups in the presence of ester, olefin, halogen, thioether, sulfonyl, cyano as well as heteroaromatic groups.
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28422240/zwitterionic-pyrrolidene-phosphonates-inhibitors-of-the-glycoside-hydrolase-like-phosphorylase-streptomyces-coelicolor-glgei-v279s
#17
Sri Kumar Veleti, Cecile Petit, Donald R Ronning, Steven J Sucheck
We synthesized and evaluated new zwitterionic inhibitors against glycoside hydrolase-like phosphorylase Streptomyces coelicolor (Sco) GlgEI-V279S which plays a role in α-glucan biosynthesis. Sco GlgEI-V279S serves as a model enzyme for validated anti-tuberculosis (TB) target Mycobacterium tuberculosis (Mtb) GlgE. Pyrrolidine inhibitors 5 and 6 were designed based on transition state considerations and incorporate a phosphonate on the pyrrolidine moiety to expand the interaction network between the inhibitor and the enzyme active site...
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28421212/cp-co-iii-catalyzed-ortho-amidation-of-azobenzenes-with-dioxazolones
#18
Gongutri Borah, Preetismita Borah, Pitambar Patel
Cp*Co(iii)-catalyzed C-H amidation of azobenzene with dioxazolones has been developed. The amidation reaction does not require external oxidants and gives carbon dioxide as the only by-product. Both symmetrical and unsymmetrical azobenzenes were found to undergo amidation smoothly with broad functional group tolerance.
April 19, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28406521/dissection-of-the-neocarazostatin-a-c4-alkyl-side-chain-biosynthesis-by-in-vitro-reconstitution
#19
Li Su, Rui Zhang, Kwaku Kyeremeh, Zixin Deng, Hai Deng, Yi Yu
Neocarazostatin A (1) is a potent free radical scavenger possessing an intriguing tricyclic carbazole nucleus with a C4 alkyl side chain attached to ring "A". Although the biosynthetic gene cluster of 1 (nzs) has been identified, and several key steps of the pathway have been well characterized, the enzyme(s) involved in the biosynthesis of the C4 unit still remains obscure. In this work, we demonstrate that three enzymes, including one (MA37-FabG) from primary fatty acid metabolism and two pathway-specific ones (NzsE and NzsF), are responsible for the formation of the side chain precursor...
April 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28406519/syn-selective-crotylation-of-aldehydes-using-bismuth-crotyl-bromide-1-butyl-3-methylimidazolium-bromide-combination-some-synthetic-applications
#20
Dibakar Goswami, Mrunesh R Koli, Sucheta Chatterjee, Subrata Chattopadhyay, Anubha Sharma
The Bi-[bmim][Br] combination has been found to offer high syn-selectivity in the crotylation of aldehydes with crotyl bromide using practically stoichiometric amounts of the reagents. The room temperature ionic liquid (RTIL), [bmim][Br], activated Bi metal in the presence of oxygen to produce crotylbismuthdibromide, which reacted with the aldehydes at room temperature. The major anti-syn diastereomeric product obtained from the crotylation of (R)-cyclohexylideneglyceraldehyde was utilized for the synthesis of dictyostatin and cryptophycin segments, and (+)-cis-aerangis lactone, using standard synthetic protocols...
April 13, 2017: Organic & Biomolecular Chemistry
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