- Selective hydrogenation of benzoic acid to cyclohexane carboxylic acid over microwave-activated Ni/carbon catalysts
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High yields of cyclohexane carboxylic acids were obtained by direct hydrogenation of aromatic carboxylic acids over different Ni/carbon catalysts having distinctive surface properties. The catalysts were characterized by SEM, TEM, H2-TPR and N2 adsorption isotherms for the determination of BET surface area and porosity. The hydrogenation reaction was carried out in batch pressure reactor in gas-liquid phase at 200 °C. High selectivity (100%) of cyclohexane carboxylic acids at 86.2 mol% conversion of benzoic acid was achieved over microwave-activated biochar supported non-precious metal Ni catalyst. The 10%Ni/CSC-b catalyst has been investigated for hydrogenation of benzoic acid to cyclohexane carboxylic acids and shown little deactivation in stability test. The effects of Ni loading, high dispersion of Ni species, appropriate power of microwave heating and strong interaction of Ni species with carbon are of benefit to the reaction.
- Lu,Shen,He,Jing,Tao,Hu,Nie,Zhou,Xia
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- Synthesis, characterization, and nucleophilic ring opening reactions of cyclohexyl-substituted β-haloamines and aziridinium ions
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Cyclohexyl-substituted β-haloamines and aziridinium ions were prepared and characterized. Stereospecific ring opening of aziridinium ions was applied for efficient synthesis of vicinal amine, β-amino acid, and tetrahydroisoquinoline (THIQ) analogues. Nucleophilic ring opening reactions of aziridinium ions and N-protected aziridine analogues were for the first time comparatively studied. The result of nucleophilic reactions clearly indicates that aziridinium ions were significantly more reactive toward nucleophilic ring opening than the aziridine analogues.
- Chong, Hyun-Soon,Sun, Xiang,Chen, Yunwei,Wang, Meng
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p. 946 - 948
(2015/01/30)
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- Isothiourea-mediated asymmetric O- to C-carboxyl transfer of oxazolyl carbonates: Structure-selectivity profiles and mechanistic studies
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The structural motif within a series of tetrahydropyrimidine-based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic 19F NMR experiments used to develop a mechanistic understanding of this transformation. Copyright
- Joannesse, Caroline,Johnston, Craig P.,Morrill, Louis C.,Woods, Philip A.,Kieffer, Madeleine,Nigst, Tobias A.,Mayr, Herbert,Lebl, Tomas,Philp, Douglas,Bragg, Ryan A.,Smith, Andrew D.
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p. 2398 - 2408
(2012/03/27)
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- PEPTIDES AND PEPTIDOMIMETIC COMPOUNDS, THE MANUFACTURING THEREOF AS WELL AS THEIR USE FOR PREPARING A THERAPEUTICALLY AND/OR PREVENTIVELY ACTIVE PHARMACEUTICAL COMPOSITION
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Peptides, peptidomimetics and derivatives thereof of the general formula I: H2N-GHRPX1-β-X4X5X6X7X8X9X10-X11 (I), in which X1-X10 denote one of the 20 genetically coded amino acids, wherein X8, X9 and X10 may also denote a single chemical bond;X11 denotes OR1 in which R1 equals hydrogen or (C1-C10) alkyl NR2R3 with R2 and R3 are equal or different and denote hydrogen, (C1-C10) alkyl, or a residue —W-PEG5-60K, in which the PEG residue is attached via a suitable spacer W to the N-atom, ora residue NH—Y-Z-PEG5-60K, in whichY denotes a chemical bond or a genetically coded amino acids from the group S, C, K or R andZ denotes a spacer, via which a polyethylene glycol (PEG)-residue can be attached, and their physiologically acceptable salts, andβ denotes an amino acid, or a peptidomimetic element, which induces a bend or turn in the peptide backbone.
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- Synthesis and characterisation of helical β-peptide architectures that contain (S)-β3-HDOPA(crown ether) derivatives
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A new set of β-amino acids that carry various crown ether receptors on their side chains of the general formula (S)-β3-HDOPA(crown ether) (HDOPA: homo-3,4-dihydroxyphenylalanine; (crown ether): [15]crown-5 ([15-C-5]), [18]crown-6 ([18-C-6]), [21]crown-7 ([21-C-7]), 1,2-Benzo-[24]crown- 8 ([Benzo-24-C-8]) and (R)-Binol-[20]crown-6 ([(R)-Binol-20-C-6])) was prepared. Peptides that are based on these new crowned β-amino acids combined with (1S,2S)-ACHC (2-aminocyclohexanecarboxylic acid), which is known to be a potent 314-helix inducer, to the hexamer level, with two crowned residues at the i and i+3 posi_tions of the main-chain, were synthesized in solution by stepwise coupling using Boc-Na-protection (Boc: tert-butoxycarbonyl) and the EDC/HOAt Cactivation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 314-helix conformation.
- Dutot, Laurence,Gaucher, Anne,Elkassimi, Khadidja,Drapeau, Jeremy,Wakselman, Michel,Mazaleyrat, Jean-Paul,Peggion, Cristina,Formaggio, Fernando,Toniolo, Claudio
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supporting information; scheme or table
p. 3154 - 3163
(2009/04/11)
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- Toward a rational design of the assembly structure of polymetallic asymmetric catalysts: design, synthesis, and evaluation of new chiral ligands for catalytic asymmetric cyanation reactions
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New chiral ligands (4 and 5) for polymetallic asymmetric catalysts were designed based on the hypothesis that the assembled structure should be stable when made from a stable module 8. A metal-ligand=5:6+μ-oxo+OH complex was generated from Gd(OiPr)3 and 4 or 5, and this complex was an improved asymmetric catalyst for the desymmetrization of meso-aziridines with TMSCN and conjugate addition of TMSCN to α,β-unsaturated N-acylpyrroles, compared to the previously reported catalysts derived from 1-3. These two groups of catalysts produced opposing enantioselectivity even though the ligands had the same chirality. The functional difference in the asymmetric catalysts is derived from differences in the higher-order structure of the polymetallic catalysts.
- Fujimori, Ikuo,Mita, Tsuyoshi,Maki, Keisuke,Shiro, Motoo,Sato, Akihiro,Furusho, Sanae,Kanai, Motomu,Shibasaki, Masakatsu
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p. 5820 - 5831
(2008/02/03)
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- Catalytic enantioselective desymmetrization of meso-N-acylaziridines with TMSCN
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A catalytic enantioselective desymmetrization of meso-N-p-nitrobenzoylaziridines with TMSCN was developed using a chiral gadolinium catalyst generated from Gd(OiPr)3 and d-glucose-derived ligand 1. In this reaction, the addition of a
- Mita, Tsuyoshi,Fujimori, Ikuo,Wada, Reiko,Wen, Jianfeng,Kanai, Motomu,Shibasaki, Masakatsu
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p. 11252 - 11253
(2007/10/03)
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- Synthesis of enantiopure cis- and trans-2-aminocyclohexane-1-carboxylic acids from octahydroquinazolin-4-ones
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The chemoselective and diastereoselective hydrogenation of 2,3-dihydro-3-[(S)-α-methylbenzyl]-4-quinazolinone 2 affords octahydroquinazolinones cis-3 and cis-4. Epimerization of cis-3 and cis-4 using t-BuO-K+ produces trans-5 and tra
- Priego, Jaime,Flores, Patricia,Ortiz-Nava, Claudia,Escalante, Jaime
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p. 3545 - 3549
(2007/10/03)
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- Heterogeneous foldamers containing alpha, beta, and/or gamma-amino acids
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Disclosed are isolated, unnatural polypeptides containing cyclically-constrained β-amino acid residues and cyclically-constrained γ-amino acid residues. The compounds are unnatural and because they contain rotationally constrained residues that are not amenable to enzymatic degradation, the compounds are useful to probe protein-protein and other large molecule interactions.
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- Asymmetric synthesis of a new helix-forming β-amino acid: trans-4-aminopiperidine-3-carboxylic acid
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We report a synthesis of a protected derivative of trans-4aminopiperidine-3-carboxylic acid (APiC). The route provides either enantiomer. All intermediates are purified by crystallization, and large-scale preparation is therefore possible. An analogous ro
- Schinnerl, Marina,Murray, Justin K.,Langenhan, Joseph M.,Gellman, Samuel H.
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p. 721 - 726
(2007/10/03)
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- Experimental determination of the absolute enantioselectivity of an antibody-catalyzed Diels-Alder reaction and theoretical explorations of the origins of stereoselectivity
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The exo and endo Diels-Alder adducts of p-methoxycarbonylbenzyl trans-1,3-butadiene-1-carbamate and N,N-dimethylacrylamide have been synthesized, and the absolute configurations of resolved enantiomers have been determined. On the basis of this information, the absolute enantioselectivities of the Diels-Alder reaction catalyzed by antibodies 13G5 and 4D5 as well as other catalytic antibodies elicited in the same immunizations have been established. The effects of different arrangements of catalytic residues on the structure and energetics of the possible Diels-Alder transition states were modeled quantum mechanically at the B3LYP/6-311++G**//B3LYP/6-31+G** level of theory. Flexible docking of these enantiomeric transition states in the antibody active site followed by molecular dynamics on the resulting complexes provided a prediction of the transition -state binding modes and an explanation of the origin of the observed enantioselectivity of antibody 13G5.
- Cannizzaro, Carina E.,Ashley, Jon A.,Janda,Houk
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p. 2489 - 2506
(2007/10/03)
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- Structure - Activity studies of 14-helical antimicrobial β-peptides: Probing the relationship between conformational stability and antimicrobial potency
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Antimicrobial α-helical α-peptides are part of the host-defense mechanism of multicellular organisms and could find therapeutic use against bacteria that are resistant to conventional antibiotics. Recent work from Hamuro et al. has shown that oligomers of
- Raguse, Tami L.,Porter, Emilie A.,Weisblum, Bernard,Gellman, Samuel H.
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p. 12774 - 12785
(2007/10/03)
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- 1, 2-Disubstituted cyclohexane derived tripeptide aldehydes as novel selective thrombin inhibitors
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A series of tripeptide arginine aldehydes was synthesized by replacement of proline with 1,2-disubstituted cyclohexane derivatives in the sequence of D-MePhe-Pro-Arg-H. Based on molecular modeling, further modification of the D-MePhe residue resulted in a potent and selective thrombin inhibitor.
- Harmat, Nicholas J.S.,Di Bugno, Cristina,Criscuoli,Giorgi, Raffaello,Lippi, Annalisa,Martinelli, Adriano,Monti, Susanna,Subissi
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p. 1249 - 1254
(2007/10/03)
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- A Method for Determinig Absolute Configuration of Cycloalkanamines and Related Compounds by CD Spectra of Their 2,4-Dinitrophenyl Derivatives
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N-(2,4-Dinitrophenyl) derivatives of cycloalkanamines and related compounds having an amino and an aromatic groups in vicinal positions were prepared.Their CD spectra exhibited marked Cotton effect around 400nm, the sign of which was shown to coincide wit
- Kawai, Masao,Iwase, Teruhiko,Butsugan, Yasuo,Nagai, Ukon
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p. 304 - 308
(2007/10/02)
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- Platinum complex
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New platinum complex represented by the general formula [I]: STR1 wherein R1 and R2 are same and represent halogen atom or NO3, or R1 is SO4 and R2 is H2 O, or R1 and R2 are bonded with each other to form either STR2 and the configuration of 1-aminomethyl-2-aminocyclohexane is selected from trans-1, trans-d, cis-1 and cis-d. The compounds of the formula [I] are active against tumor and are expected to be useful as medicaments.
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