- Asymmetric Catalytic Approach to Multilayer 3D Chirality
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The first asymmetric catalytic approach to multilayer 3D chirality has been achieved by using Suzuki-Miyaura cross-couplings. New chiral catalysts were designed and screened under various catalytic systems that proved chiral amide-phosphines to be more efficient ligands than other candidates. The multilayer 3D framework was unambiguously determined by X-ray structural analysis showing a parallel pattern of three layers consisting of top, middle and bottom aromatic rings. The X-ray structure of a catalyst complex, dichloride complex of Pd-phosphine amide, was obtained revealing an interesting asymmetric environment nearby the Pd metal center. Three rings of multilayer 3D products can be readily changed by varying aromatic ring-anchored starting materials. The resulting multilayer products displayed strong luminescence under UV irradiation and strong aggregation-induced emission (AIE). In the future, this work would benefit not only the field of asymmetric synthesis but also materials science, in particular polarized organic electronics, optoelectronics and photovoltaics.
- Wu, Guanzhao,Liu, Yangxue,Rouh, Hossein,Ma, Liulei,Tang, Yao,Zhang, Sai,Zhou, Peng,Wang, Jia-Ying,Jin, Shengzhou,Unruh, Daniel,Surowiec, Kazimierz,Ma, Yanzhang,Li, Guigen
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p. 8013 - 8020
(2021/05/10)
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- syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
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Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
- Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
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p. 3604 - 3612
(2021/07/26)
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- A new type of L-Tertiary leucine-derived ligand: Synthesis and application in Cu(II)-catalyzed asymmetric Henry reactions
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A new series of Schiff bases derived from amino acids were developed as chiral ligands for Cu(II)-catalyzed asymmetric Henry reactions. The optimum ligand 7d exhibited outstanding catalytic efficiency in the Cu(II)-catalyzed asymmetric Henry additions of four nitroalkanes to different kinds of aldehydes to produce 76 desired adducts in high yields (up to 96%) with excellent enantioselectivities, up to 99% enantiomeric excess (ee).
- Cai, Zedong,Lan, Ting,Ma, Pengfei,Zhang, Jingfang,Yang, Qingqing,He, Wei
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- Chiral primary amine catalyzed asymmetric direct cross-aldol reaction of acetaldehyde
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The first primary aminocatalytic direct cross-aldol reaction of acetaldehyde is presented. Among the various vicinal diamines screened, the L-tert-leucine derivative 1c in conjunction with (H4SiW 12O40)0.25 was identified as the optimal catalyst; good catalytic activity (up to 99% yield in 4 h), and high enantioselectivities (up to 92% ee) were achieved for a range of donors, including aromatic aldehydes and isatin derivatives. Aqueous acetaldehyde solution and paraldehyde can be conveniently applied in this system.
- Hu, Shenshen,Zhang, Long,Li, Jiuyuan,Luo, Sanzhong,Cheng, Jin-Pei
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p. 3347 - 3352
(2011/08/03)
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- Highly enantio- and diastereoselective synthesis of α- trifluoromethyldihydropyrans using a novel bifunctional piperazine-thiourea catalyst
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The first enantioselective Michael addition of α-cyanoketones to α,β-unsaturated trifluoromethyl ketones using a novel piperazine-thiourea catalyst was described. The resulting α- trifluoromethyldihydropyrans were obtained in high yields and with up to 95
- Li, Peng,Chai, Zhuo,Zhao, Sheng-Li,Yang, Ying-Quan,Wang, Hai-Feng,Zheng, Chang-Wu,Cai, Yue-Peng,Zhao, Gang,Zhu, Shi-Zheng
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supporting information; experimental part
p. 7369 - 7371
(2010/06/14)
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- Aminocarbonyloxymethyl ester prodrugs of flufenamic acid and diclofenac: Suppressing the rearrangement pathway in aqueous media
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Aminocarbonyloxymethyl ester prodrugs are known to undergo rearrangement in aqueous solutions to form the corresponding N-acylamine side product via an O → N intramolecular acyl transfer from the carbamate conjugate base. Novel aminocarbonyloxymethyl esters of diclofenac and flufenamic acid containing amino acid amide carriers were synthesized and evaluated as potential prodrugs displaying less ability to undergo rearrangement. These compounds were prepared in reasonable yield by a four-step synthetic method that uses the appropriate N-Boc-protected amino acid N-hydroxysuccinimide ester and secondary amine and chloromethyl chloroformate as key reactants. Their reactivity in pH 7.4 buffer and 80% human plasma at 37°C was assessed by RP-HPLC. The aminocarbonyloxymethyl esters containing a secondary carbamate group derived from amino acids such as glycine or phenylalanine were hydrolyzed quantitatively to the parent drug both in non-enzymatic and enzymatic conditions, with no rearrangement product being detected. The oral bioavailability in rats was determined for selected diclofenac derivatives. These derivatives displayed a bioavailability of 25 to 68% relative to that of diclofenac, probably due to their poor aqueous solubility and lipophilicity. These results suggest that further optimization of aminocarbonyloxymethyl esters as potential prodrugs for non-steroidal anti-inflammatory drugs require the use of amino acid carriers with ionizable groups to improve aqueous solubility.
- Ribeiro, Lina,Silva, Nuno,Iley, Jim,Rautio, Jarkko,Jaervinen, Tomi,Mota-Filipe, Helder,Moreira, Rui,Mendes, Eduarda
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