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https://www.readbyqxmd.com/read/28092703/enantioselective-three-component-amination-of-enecarbamates-enables-the-synthesis-of-structurally-complex-small-molecules
#1
Audrey Dumoulin, Guillaume Bernadat, Géraldine Masson
The control of asymmetric synthesis tools represents a major challenge, especially when it comes to the synthesis of bioactive molecules. In this context, the asymmetric synthesis of 1,2-diamines through amination of enecarbamates has appeared to us as a highly efficient and tunable approach. Indeed, reactivity of the latter species could be exploited to realize a double functionalization via an electrophilic amination followed by nucleophilic trapping. Herein, we describe a chiral phosphoric acid-catalyzed electrophilic amination of enecarbamates with dibenzylazodicarboxylate and oxygenated or thiol-containing nucleophiles affording stable precursors of α-hydrazinoimines in high yields and with almost complete enantioselectivities (up to >99%)...
January 16, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28089449/transferase-versus-hydrolase-the-role-of-conformational-flexibility-in-reaction-specificity
#2
Samuel H Light, Laty A Cahoon, Kiran V Mahasenan, Mijoon Lee, Bill Boggess, Andrei S Halavaty, Shahriar Mobashery, Nancy E Freitag, Wayne F Anderson
Active in the aqueous cellular environment where a massive excess of water is perpetually present, enzymes that catalyze the transfer of an electrophile to a non-water nucleophile (transferases) require specific strategies to inhibit mechanistically related hydrolysis reactions. To identify principles that confer transferase versus hydrolase reaction specificity, we exploited two enzymes that use highly similar catalytic apparatuses to catalyze the transglycosylation (a transferase reaction) or hydrolysis of α-1,3-glucan linkages in the cyclic tetrasaccharide cycloalternan (CA)...
January 5, 2017: Structure
https://www.readbyqxmd.com/read/28088623/a-novel-role-of-topical-iodine-in-skin-activation-of-the-nrf2-pathway
#3
Maya Ben-Yehuda Greenwald, Marina Frušić-Zlotkin, Yoram Soroka, Shmuel Ben-Sasson, Havazelet Bianco-Peled, Ron Kohen
For a long time iodine has been used as an active dermal agent in the treatment of inflammatory, immune-mediated and infectious diseases. Moreover, topical iodine application has been reported to provide protection against sulfur-mustard-induced skin lesions, heat-induced and acid-induced skin burns in both haired guinea-pigs and mouse ear swelling models. However, the exact mechanism of action underlying these benefits of iodine has not yet been elucidated. In the current study, a novel mechanism of action by which iodine provides skin protection and relief, based on its electrophilic nature, is suggested...
January 11, 2017: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/28087294/bioactive-metabolites-of-docosahexaenoic-acid
#4
REVIEW
Ondrej Kuda
Docosahexaenoic acid (DHA) is an essential fatty acid that is recognized as a beneficial dietary constituent and as a source of the anti-inflammatory specialized proresolving mediators (SPM): resolvins, protectins and maresins. Apart from SPMs, other metabolites of DHA also exert potent biological effects. This article summarizes current knowledge on the metabolic pathways involved in generation of DHA metabolites. Over 70 biologically active metabolites have been described, but are often discussed separately within specific research areas...
January 10, 2017: Biochimie
https://www.readbyqxmd.com/read/28075598/organocatalytic-regioselective-concomitant-thiocyanation-and-acylation-of-oxiranes-using-aroyl-isothiocyanates
#5
Anju Modi, Wajid Ali, Bhisma K Patel
A regioselective and concomitant transfer of thiocyanate (-SCN) and aroyl/acyl (-COR) groups from aroyl/acyl isothiocyanates onto oxiranes was achieved, giving thiocyanato benzoates in 100% atom economy. In this biomimetic organocatalytic process, one part (-SCN) of aroyl/acyl isothiocyanates acts as the nucleophile whereas the other half (-COR) serves as an electrophilic partner.
January 11, 2017: Organic Letters
https://www.readbyqxmd.com/read/28074930/mechanism-reactivity-and-regioselectivity-in-rhodium-catalyzed-asymmetric-ring-opening-reactions-of-oxabicyclic-alkenes-a-dft-investigation
#6
Zheng-Hang Qi, Yi Zhang, Yun Gao, Ye Zhang, Xing-Wang Wang, Yong Wang
The origin of the enantio- and regioselectivity of ring-opening reaction of oxabicyclic alkenes catalyzed by rhodium/Josiphos has been examined using M06-2X density functional theory(DFT). DFT calculations predict a 98% ee for the enantioselectivity and only the 1,2-trans product as one regio- and diastereomer, in excellent agreement with experimental results. The solvent tetrahydrofuran(THF) plays a key role in assisting nucleophilic attack. Orbital composition analysis of the LUMO and the NPA atomic charge calculations were conducted to probe the origins of the regioselectivity...
January 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28071829/gold-catalyzed-intermolecular-formal-insertion-of-aryldiazo-esters-into-cp-h-bonds-of-cp%C3%A2-m-m-fe-ru
#7
Enol López, Javier Borge, Luis A López
The reaction of ferrocene (and ruthenocene) with aryldiazo acetates in the presence of gold catalysts provided new functionalized metallocenes resulting from a C-H bond functionalization process. This process is believed to proceed through initial decomposition of the diazo component with formation of an electrophilic gold carbene intermediate, which would be subsequently involved in an electrophilic aromatic substitution. The gold-catalyzed functionalization of ruthenocene exhibited a broad scope and a notable functional-group tolerance...
January 10, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28070082/evaluation-of-structural-isomers-molecular-interactions-reactivity-descriptors-and-vibrational-analysis-of-tretinoin
#8
T Karthick, Poonam Tandon, Swapnil Singh
Tretinoin is known to be a pharmaceutical drug for treating acne vulgaris, keratosis pilaris, and acute promyelocytic leukemia. In order to reveal the possible conformers of tretinoin, the energies of all the conformers through rotational bonds have been evaluated by systematic rotor search analysis. The intramolecular interactions ranging from strong hydrogen bonds to weak van der Waals forces present in tretinoin have been distinguished with the help of electron density mapping and wavefunction analysis. The global reactivity descriptors and Fukui functions of tretinoin have been calculated and discussed...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
https://www.readbyqxmd.com/read/28067451/iridium-catalyzed-intermolecular-asymmetric-dearomatization-of-%C3%AE-naphthols-with-allyl-alcohols-or-allyl-ethers
#9
Hang-Fei Tu, Chao Zheng, Ren-Qi Xu, Xi-Jia Liu, Shu-Li You
An Ir-catalyzed intermolecular asymmetric dearomatization reaction of β-naphthols with allyl alcohols or allyl ethers was developed. When an iridium catalyst generated from [Ir(COD)Cl]2 (COD=cyclooctadiene) and a chiral P/olefin ligand is employed, highly functionalized β-naphthalenone compounds bearing an all-carbon-substituted quaternary chiral center were obtained in up to 92 % yield and 98 % ee. The direct utilization of allyl alcohols as electrophiles represents an improvement from the viewpoint of atom economy...
January 9, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28067446/synergistic-diastereo-and-enantioselective-functionalization-of-unactivated-alkyl-quinolines-with-%C3%AE-%C3%AE-unsaturated-aldehydes
#10
Marta Meazza, Fernando Tur, Niels Hammer, Karl Anker Jørgensen
A novel alkyl functionalization of unactivated alkyl quinolines has been developed combining InCl3 activation with organocatalytic activation of α,β-unsaturated aldehydes in a synergistic fashion. The reaction proceeds in a highly stereoselective manner as a sequence involving two consecutive synergistic catalytic cycles (Lewis acid- and iminium ion-catalyzed) and requires neither pre-activated alkyl quinoline substrates with electron-withdrawing substituents nor highly activated electrophiles. The reaction provides selectively double- or mono-addition products in good yields and high to excellent stereoselectivities...
January 9, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28066540/non-directed-aromatic-c-h-amination-catalytic-and-mechanistic-studies-enabled-by-pd-catalyst-and-reagent-design
#11
H M D Bandara, D Jin, M A Mantell, K D Field, A Wang, R P Narayanan, N A Deskins, M H Emmert
This manuscript describes the systematic development of pyridine-type ligands, which promote the Pd catalyzed, non-directed amination of benzene in combination with novel, hydroxylamine-based electrophilic amination reagents. DFT calculations and mechanistic experiments provide insights into the factors influencing the arene C-H amination protocol.
July 21, 2016: Catalysis Science & Technology
https://www.readbyqxmd.com/read/28062194/hetero-diels-alder-approach-to-bis-indolyl-methanes
#12
Carla Grosso, Ana L Cardoso, Maria João Rodrigues, Cátia Marques, Luísa Barreira, Américo Lemos, Teresa M D V Pinho E Melo
A novel synthetic approach to bis(indolyl)methanes has been established. Our one-pot synthetic strategy based on two consecutive hetero-Diels-Alder cycloaddition reactions of electrophilic conjugated nitrosoalkenes with indoles was extended to a range of new 1-hydroxyiminomethyl-bis(indolyl)methanes. Furthermore, a similar and broad range approach was applied to the synthesis of previously unknown 1-hydrazonomethyl-bis(indolyl)methanes. The biological evaluation of the new bis(indolyl)methanes as anti-cancer agents was investigated...
December 26, 2016: Bioorganic & Medicinal Chemistry
https://www.readbyqxmd.com/read/28060514/targeted-covalent-inhibition-of-grb2-sos1-interaction-through-proximity-induced-conjugation-in-breast-cancer-cells
#13
Yongsheng Yu, Yunyu Nie, Qian Feng, Jiale Qu, Rui Wang, Liming Bian, Jiang Xia
Targeted covalent inhibitors of protein-protein interactions differ from reversible inhibitors in that the former bind and covalently bond the target protein at a specific site of the target. The site specificity is the result of the proximity of two reactive groups at the bound state, for example one mild electrophile in the inhibitor and a natural cysteine in the target close to the ligand binding site. Only a few pharmaceutically relevant proteins have this structural feature. Grb2, a key adaptor protein in maintaining the ERK activity via binding Sos1 to activated RTKs, is one: the N-terminal SH3 domain of Grb2 (Grb2N-SH3) carries a unique solvent-accessible cysteine Cys32 close to its Sos1-binding site...
January 6, 2017: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/28059507/catalytic-asymmetric-bromocyclization-of-polyenes
#14
Ramesh C Samanta, Hisashi Yamamoto
The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28059403/coupling-of-c-sp-3-h-bonds-with-c-sp-2-o-electrophiles-mild-general-and-selective
#15
Yong-Yuan Gui, Li-Li Liao, Liang Sun, Zhen Zhang, Jian-Heng Ye, Guo Shen, Zhi-Peng Lu, Wen-Jun Zhou, Da-Gang Yu
Herein is reported the mild and general coupling of amine/ether C(sp(3))-H bonds with various kinds of C(sp(2))-O electrophiles with high selectivity and efficiency. Valuable allylic/benzylic amines are generated in moderate to excellent yields. The utility of this transformation is demonstrated by a broad substrate scope (>50 examples), good functional group tolerance and facile product modification.
January 6, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28058783/characterization-of-phase-i-and-phase-ii-hepatic-metabolism-and-reactive-intermediates-of-larrea-nitida-cav-and-its-lignan-compounds
#16
Hyesoo Jeong, Soolin Kim, Jimin Lee, Jin Young Park, Wenmei Zhou, Xiyuan Liu, So Dam Kim, Yun Seon Song, Chang-Young Jang, Sei-Ryang Oh, Sangho Choi, Minsun Chang
Larrea nitida Cav. (LNC), which belongs to the family Zygophyllaceae, is widely indigenous and used in South America to treat various pathological conditions. It contains the antioxidant and antiinflammatory but toxic nordihydroguaiaretic acid (NDGA) as well as O-methylated metabolite of NDGA (MNDGA) as bioactive compounds. The hepatic metabolism-based toxicological potential of extracts of LNC (LNE), NDGA, and MNDGA has not previously been reported. The present study aimed to characterize the phase I and phase II hepatic metabolism and reactive intermediates of LNE, NDGA, and MNDGA and their effects on the major drug-metabolizing enzymes in vitro and ex vivo...
January 2017: Phytotherapy Research: PTR
https://www.readbyqxmd.com/read/28058283/insight-into-transmetalation-enables-cobalt-catalyzed-suzuki-miyaura-cross-coupling
#17
Jamie M Neely, Máté J Bezdek, Paul J Chirik
Among the fundamental transformations that comprise a catalytic cycle for cross coupling, transmetalation from the nucleophile to the metal catalyst is perhaps the least understood. Optimizing this elementary step has enabled the first example of a cobalt-catalyzed Suzuki-Miyaura cross coupling between aryl triflate electrophiles and heteroaryl boron nucleophiles. Key to this discovery was the preparation and characterization of a new class of tetrahedral, high-spin bis(phosphino)pyridine cobalt(I) alkoxide and aryloxide complexes, ((iPr)PNP)CoOR, and optimizing their reactivity with 2-benzofuranylBPin (Pin = pinacolate)...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28055213/mechanism-of-an-organoboron-catalyzed-domino-reaction-kinetic-and-computational-studies-of-borinic-acid-catalyzed-regioselective-chloroacylation-of-2-3-epoxy-alcohols
#18
Graham E Garrett, Kashif Tanveer, Mark S Taylor
A mechanistic study of the borinic acid-catalyzed chloroacylation of 2,3-epoxy alcohols is presented. In this unusual mode of catalysis, the borinic acid activates the substrate toward sequential reactions with a nucleophile (epoxide ring-opening by chloride) and an electrophile (O-acylation of the resulting alkoxide). Reaction progress kinetic analysis of data obtained through in situ FTIR spectroscopy is consistent with a mechanism involving turnover-limiting acylation of a chlorohydrin-derived borinic ester...
January 5, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28055208/thiol-based-probe-for-electrophilic-natural-products-reveals-that-most-of-the-ammosamides-are-artifacts
#19
Daniela Reimer, Chambers C Hughes
To date, 16 members of the ammosamide family of natural products have been discovered, and except for ammosamide D each of these metabolites is characterized by an unusual chlorinated pyrrolo[4,3,2-de]quinoline skeleton. Several ammosamides have been shown to inhibit quinone reductase 2, a flavoenzyme responsible for quelling toxic oxidative species in cells or for killing cancer cells outright. Treatment of the extract from an ammosamide-producing culture (Streptomyces strain CNR-698) with a thiol-based reagent designed to label electrophilic natural products produced an ammosamide C-thiol adduct...
January 5, 2017: Journal of Natural Products
https://www.readbyqxmd.com/read/28054785/nickel-catalyzed-reductive-conjugate-addition-of-primary-alkyl-bromides-to-enones-to-form-silyl-enol-ethers
#20
Kierra M M Huihui, Ruja Shrestha, Daniel J Weix
Conjugate addition of organometallic reagents to enones to form silyl enol ether products is a versatile method to difunctionalize activated olefins, but the organometallic reagents required can be limiting. The reductive cross-electrophile coupling of unhindered primary alkyl bromides with enones and chlorosilanes to form silyl enol ether products is catalyzed by a nickel-complexed ortho-brominated terpyridine ligand. The conditions are compatible with a variety of cyclic/acyclic enones and functional groups...
January 5, 2017: Organic Letters
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