- Scorpio-Ligand: Synthesis of Biphenyl-Dihydroazepine Phosphoramidite Ligands for Asymmetric Hydrogenation
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A novel dihydroazepine-bridged BIPHEP phosphoramidite ligand with an amino acid moiety in the backbone was synthesized and evaluated in the Rh-catalyzed asymmetric hydrogenation. The scorpion tail-like amino acid backbone is capable of hydrogen bond forma
- Auras, Stefanie,Trapp, Oliver
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- Nickel-Catalyzed Asymmetric Hydrogenation of 2-Amidoacrylates
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Earth-abundant nickel, coordinated with a suitable chiral bisphosphine ligand, was found to be an efficient catalyst for the asymmetric hydrogenation of 2-amidoacrylates, affording the chiral α-amino acid esters in quantitative yields and excellent enantioselectivity (up to 96 % ee). The active catalyst component was studied by NMR and HRMS, which helped us to realize high catalytic efficiency on a gram scale with a low catalyst loading (S/C=2000). The hydrogenated products could be simply converted into chiral α-amino acids, β-amino alcohols, and their bioactive derivatives. Furthermore, the catalytic mechanism was investigated using deuterium-labeling experiments and computational calculations.
- Chen, Jianzhong,Gridnev, Ilya D.,Hu, Yawen,Li, Bowen,Zhang, Wanbin,Zhang, Zhenfeng
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supporting information
p. 5371 - 5375
(2020/02/15)
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- Pd(II)-Catalyzed [4 + 2] Heterocyclization Sequence for Polyheterocycle Generation
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A new Pd(II)-catalyzed cascade sequence for the formation of polyheterocycles, from simple starting materials, is reported. The sequence is applicable to both indole and pyrrole substrates, and a range of substituents are tolerated. The reaction is thought to proceed by a Pd(II)-catalyzed C-H activated Heck reaction followed by a second Pd(II)-catalyzed aza-Wacker reaction with two Cu(II)-mediated Pd(0) turnovers per sequence. The sequence can be considered a formal [4 + 2] heterocyclization.
- Glaisyer, Elizabeth L.,Watt, Michael S.,Booker-Milburn, Kevin I.
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supporting information
p. 5877 - 5880
(2018/09/25)
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- Chromatographic enantiomer separation using 9-amino-9-(deoxy)-epiquinine- derived chiral selectors: Control of chiral recognition via introduction of additional stereogenic centers
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Three new cinchona-type chiral selectors have been prepared by attaching N-pivaloyl-glycine, N-pivaloyl-(S)-valine and N-pivaloyl-(R)-valine segments to the C9-amino function of 9-amino-9-(deoxy)-epiquinine (eAQN), and immobilized to silica to provide the corresponding chiral stationary phases (CSPs). Evaluation of the chromatographic enantioseparation characteristics of these CSPs with a broad assortment of N-carbamoyl protected amino acids under polar organic mobile phase conditions revealed modest chiral recognition capabilities for N-Fmoc-, N-Cbz- and N-Boc-derivatives. It was found that the enantioselective analyte binding to these CSPs is strictly controlled by the absolute stereochemistry of the amino acid functionalities attached to the C9-amino group of the eAQN framework. Specifically, the CSP derived from (S)-valine-based selector exhibits preferential binding of N-carbamoyl-(S)-amino acids, while the CSPs featuring (R)-valine- and the glycine-derived selectors show opposite enantioselective binding preference. The observed impact of analyte structure on enantioselectivity and the specific preferences in enantioselective binding point to chiral recognition mechanisms capitalizing on intermolecular ion pairing, hydrogen bonding and subtle steric interactions, with the latter making the crucial contributions to stereodiscrimination. The finding that the chiral recognition characteristics of epiquinine can be readily controlled via incorporation of additional stereogenic centers remote from the cinchona scaffold might be useful information for the design of new enantioselective receptors and organocatalysts.
- Maier, Norbert M.,Greco, Elisa,Petrovaj, Jan,Lindner, Wolf Gang
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p. 454 - 463
(2012/11/13)
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- PYRONE COMPOUND AND ITS USE FOR PEST CONTROL
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A pyrone compound represented by formula (1) has an excellent controlling effect on pests. Since the compound of formula (1) has a controlling activity on pests, the compound is useful as an active ingredient of a pest control agent.
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Page/Page column 285
(2011/05/06)
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- Functionalizing glycine derivatives by direct C-C bond formation
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(Chemical Equation Presented) Come on glycine: Two different types of glycine derivatives are α-functionalized using cross-dehydrogenative- coupling (CDC) reactions. The method allows the efficient attachment of a malonate or aromatic alkyne group on the α-position of the glycine derivatives under very mild conditions.
- Zhao, Liang,Li, Chao-Jun
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supporting information; experimental part
p. 7075 - 7078
(2009/04/07)
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- Resonance Raman examination of the electronic excited states of glycylglycine and other dipeptides: Observation of a carboxylate→amide charge transfer transition
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We have examined the UV resonance Raman and the VUV absorption spectra of aqueous glycylglycine and other dipeptides. We observe strong resonance Raman enhancement of the amide I, II, and III bands and the amide CαH bending mode in a manner sim
- Chen,Li, Pusheng,Holtz, Janet S.W.,Chi, Zhenhuan,Pajcini, Vasil,Asher, Sanford A.,Kelly, Lisa A.
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p. 9705 - 9715
(2007/10/03)
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- The Alkylation of Menthyl Hippurate and Some Related Materials: A Reinvestigation.
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Benzylation of chiral esters of N-acyglycines using various bases and additives was examined.No C-alkylation was observed with one equivalent of base.Diastereoselectivities were dependent on the amount of additive, the nature of the N-acyl group, and the chiral ester.A model to account for the degree and sense of the stereoselectivity is proposed.
- McIntosh, John M.,Thangarasa, Rasiah,Foley, Nancy K.,Ager, David J.,Froen, Diane E.,Klix, Russell C.
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p. 1967 - 1974
(2007/10/02)
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