- Beyond Amphiphilic Balance: Changing Subunit Stereochemistry Alters the Pore-Forming Activity of Nylon-3 Polymers
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Amphiphilic nylon-3 polymers have been reported to mimic the biological activities of natural antimicrobial peptides, with high potency against bacteria and minimal toxicity toward eukaryotic cells. Amphiphilic balance, determined by the proportions of hydrophilic and lipophilic subunits, is considered one of the most important features for achieving this activity profile for nylon-3 polymers and many other antimicrobial polymers. Insufficient hydrophobicity often correlates with weak activities against bacteria, whereas excessive hydrophobicity correlates with high toxicity toward eukaryotic cells. To ask whether factors beyond amphiphilic balance influence polymer activities, we synthesized and evaluated new nylon-3 polymers with two stereoisomeric subunits, each bearing an ethyl side chain and an aminomethyl side chain. Subunits that differ only in stereochemistry are predicted to contribute equally to amphiphilic balance, but we observed that the stereochemical difference correlates with significant changes in biological activity profile. Antibacterial activities were not strongly affected by subunit stereochemistry, but the ability to disrupt eukaryotic cell membranes varied considerably. Experiments with planar lipid bilayers and synthetic liposomes suggested that eukaryotic membrane disruption results from polymer-mediated formation of large pores. Collectively, our results suggest that factors other than amphiphilic balance influence the membrane activity profile of synthetic polymers. Subunits that differ in stereochemistry are likely to have distinct conformational propensities, which could potentially lead to differences in the average shapes of polymer chains, even when the subunits are heterochiral. These findings highlight a dimension of polymer design that should be considered more broadly in efforts to improve specificity and efficacy of antimicrobial polymers.
- Liu, Lei,Courtney, Kevin C.,Huth, Sean W.,Rank, Leslie A.,Weisblum, Bernard,Chapman, Edwin R.,Gellman, Samuel H.
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- A unifying stereochemical analysis for the formation of halogenated C 15-acetogenin medium-ring ethers from laurencia species via intramolecular bromonium ion assisted epoxide ring-opening and experimental corroboration with a model epoxide
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A unifying stereochemical analysis for the formation of the constitutional isomeric halogenated C15-acetogenin medium-ring ether natural products from Laurencia species is presented, where an intramolecular bromonium ion assisted epoxide ring-o
- Bonney, Karl J.,Braddock, D. Christopher
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Read Online
- OLIGONUCLEOTIDE COMPOSITIONS AND METHODS THEREOF
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The present disclosure provides modified oligonucleotides and compositions and methods thereof. In some embodiments, provided technologies comprise modified sugars and/or modified internucleotidic linkages. In some embodiments, the present disclosure provides technologies for preparing modified oligonucleotides. In some embodiments, the present disclosure provides chirally controlled oligonucleotide compositions and methods for their preparation and uses.
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- Regiospecific Synthesis of Calcium-Independent Daptomycin Antibiotics using a Chemoenzymatic Method
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Daptomycin (DAP) is a calcium (Ca2+)-dependent FDA-approved antibiotic drug for the treatment of Gram-positive infections. It possesses a complex pharmacophore hampering derivatization and/or synthesis of analogues. To mimic the Ca2+-binding effect, we used a chemoenzymatic approach to modify the tryptophan (Trp) residue of DAP and synthesize kinetically characterized and structurally elucidated regiospecific Trp-modified DAP analogues. We demonstrated that the modified DAPs are several times more active than the parent molecule against antibiotic-susceptible and antibiotic-resistant Gram-positive bacteria. Strikingly, and in contrast to the parent molecule, the DAP derivatives do not rely on calcium or any additional elements for activity.
- Mupparapu, Nagaraju,Lin, Yu-Hsin Cindy,Kim, Tae Ho,Elshahawi, Sherif I.
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p. 4176 - 4182
(2021/02/01)
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- Formal synthesis of brivaracetam: A key to construct the pyrrolidone scaffold using Pd-catalyzed oxidative cyclization and ring-closing metathesis reaction
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A short and efficient synthetic approach for brivaracetam has been accomplished via two different routes which utilize Pd-catalyzed oxidative cyclization and ring-closing metathesis (RCM) as the key reaction. These two routes are novel, simple, scalable and rely on (E)-pent-2-en-1-ol and valeraldehyde as a commercially available starting material to yield brivaracetam with good overall yield.
- Chavan, Subhash P.,Kawale, Sanket A.,Chavan, Prakash N.
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supporting information
(2019/11/11)
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- Proof-of-principle direct double cyclisation of a linear C15-precursor to a dibrominated bicyclic medium-ring ether relevant to Laurencia species
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Bicyclic dibrominated C15 medium-ring ether hexahydrolaureoxanyne was produced directly from an acyclic model C15-epoxide when treated with NBS with water as the solvent. This journal is
- Braddock, D. Christopher,Sbircea, Dan-Tiberiu
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supporting information
p. 12691 - 12693
(2015/05/20)
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- Protective group-free syntheses of (±)-frontalin, (±)-endo-brevicomin, (±)-exo-brevicomin, and (±)-3,4- dehydro-exo-brevicomin: Racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring
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Protective group-free syntheses of four racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring were achieved in five or six steps from commercially available (±)-3-butyn-2-ol (6) and 2-alkenyl halides or 2-alken-1-ol by employing Lewis acid-catalyzed acetalization of δ, ε-epoxy ketones as the key reaction. (±)- Frontalin (1) was prepared in a 25% overall yield in five steps from methallyl chloride (5a), (±)-endo-brevicomin (2) was prepared in a 23% overall yield in five steps from (E)-2-pentenyl bromide (5b), and (±)-exo-brevicomin (3) and (±)-3,4-dehydro-exo-brevicomin (4) were both prepared in a 4%overall yield in six steps based on (Z)-2-penten-1-ol (12).
- Mori, Kenji
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body text
p. 976 - 981
(2012/01/05)
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- Unexpected electrophilic rearrangements of amides: A stereoselective entry to challenging substituted lactones
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"Chemical Equation Presented" Surprise, surprise! An unexpected skeletal rearrangement was developed into a chemo- and stereoselective synthesis of aallyl and allenyl lactones with challenging substitution patterns (see scheme; EWC = electron-withdrawing group). The generality, unique features, and synthetic potential of this reaction were probed and a mechanism was proposed.
- Madelaine, Claire,Valerio, Viviana,Maulide, Nuno
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supporting information; experimental part
p. 1583 - 1586
(2010/06/15)
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- Pyrrolopyridazine derivatives
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Pyrrolopyridazine derivatives having the general formula. In the above formula, R1 represents a C2-C6alkenyl-group, a halogeno-C2-C6-alkenyl group, a C6-C10 aryl-C2-C6-alkenyl group, a C2-C6 alkynyl group, a C3-C7 cycloalkyl group, a C3-C7 cycloalkyl-C1-C6-alkyl group, a C5-C7 cycloalkenyl-C1-C6-alkyl group or a halogeno-C1-C6-alkyl group; R2 and R3 are the same or different and each represents a hydrogen atom, a C1-C6 alkyl group or a C6-C10 aryl group; R4 represents a hydrogen atom or a C1-C6 alkyl group; R5 represents a C6-C10 aryl group or a 5-10 membered heteroaryl group comtaining heteroatom(s) selected from nitrogen, oxygen and sulfur;
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- Large-scale preparation of (9Z,12E)-[1-13C]-octadeca-9,12-dienoic acid, (9Z,12Z,15E)-[1-13C]-octadeca-9,12,15-trienoic acid and their [1-13C] all-cis isomers
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Several grams of labelled trans linoleic and linolenic acids with high chemical and isomeric purities (>97%) have been prepared for human metabolism studies. A total of 12.5 g of (9Z,12E)-[1-13C]-octadeca-9,12-dienoic acid and 6.3 g of (9Z,12Z,15E)-[1-13C]-octadeca-9,12,15-trienoic acid were obtained in, respectively, seven steps (7.8% overall yield) and 11 steps (7% overall yield) from 7-bromo-heptan-1-ol. The trans bromo precursors used for the labelling were synthesised by using copper-catalysed couplings. The trans fatty acids were then obtained via the nitrile derivatives. A total of 23.5 g of (9Z,12Z)-[1-13C]-octadeca-9,12-dienoic acid and 10.4 g of (9Z,12Z,15Z)-[1-13C]-octadeca-9,12,15-trienoic acid were prepared in five steps in, respectively, 32 and 18% overall yield. Large quantities of bromo and chloro precursors were synthesised from the commercially available acid according to Barton's procedure. In all cases, the main impurities (>0.5%) of each labelled fatty acid have been characterised. Copyright (C) 2000 Elsevier Science Ireland Ltd.
- Loreau,Maret,Poullain,Chardigny,Sebedio,Beaufrere,Noel
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- Syntheses of 2-ethyl-8-methyl-1,7-dioxaspiroundecanols
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Synthetic approaches to ring- and side-chain hydroxy derivatives of the 2-ethyl-8-methyl-1,7-dioxaspiroundecane system 8 are described.Alkylation reactions of diethyl 3-oxopentanedioate, pentane-2,4-dione and acetone N,N-dimethylhydrazone have been employed.Appropriate choices of enantiomeric iodides in the alkylation sequences, sometimes followed by asymmetric dihydroxylation of derived hydroxyenones, have permitted access to key enantiomers of these alcohols, which have been fully characterised by 1H and 13C NMR spectroscopy, gas chromatographic-mass spectrometric methods, and chiral gas chromatography.
- Jacobs, Mark F.,Suthers, Bill D.,Huebener, Achim,Kitching, William
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p. 901 - 918
(2007/10/02)
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- ENANTIOMERIC SYNTHESIS OF 6(R), 7(R) AND 6(S), 7(S) TRANS-AND CIS-LAUREDIOL
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The title compounds have been synthesized by using acetylenic coupling procedures, asymmetric epoxidation and stereo- and regio-selective openings of the epoxides.
- Anorbe, B.,Martin, V. S.,Palazon, J. M.,Trujillo, J. M.
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p. 4991 - 4994
(2007/10/02)
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- Syntheses of the Sex Pheromone of the European Pine Shoot Moth (Rhyacionia buoliana). The Grignard Route
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Grignard-Kopplungen zwischen zwei entsprechenden Synthonen fuehren zum (E)-9-Dodecen-1-ylacetat (1), dem Sexuallockstoff des Kiefernknospentriebwicklers (Rhyacionioa buoliana).Als solche Synthon-Paare wurden 1-Brom-(E)-2-penten (2) und 7-Bromheptyltetrahydropyranylether (3) bzw. (E)-3-Hexen-1-yltosylat (4) und 6-Bromhexyltrimethylsilylether (5) eingesetzt.Das Endprodukt (1) und die wichtigsten Zwischenprodukte wurden durch ihre 1H- und 13C-NMR-Spektren charakterisiert.Durch die zweite Synthese wurden 100percent Regio- und 99percent Stereoselektivitaet erreicht.
- Popovici, N.,Botar, A. A.,Barabas, A.,Oprean, I.,Hodosan, F.
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