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1.
Artigo em Inglês | MEDLINE | ID: mdl-33089632

RESUMO

Buried salt bridges widely exist in protein structures but are rarely used in synthetic systems for molecular recognition in water. By mimicking the binding pocket of bioreceptors, we designed and synthesized a pair of endo-functionalized macrocyclic hosts with secondary ammonium groups in a hydrophobic cavity. We found that these macrocycles are able to selectively recognize carboxylic acids in water through salt bridges and the hydrophobic effect. Moreover, it was demonstrated that these macrocyclic receptors can be used in circular-dichroism-based optical chirality sensing of chiral carboxylic acids and fluorescent sensing of phenylpyruvic acid-a biomarker for phenylketonuria. This research showcases that buried salt bridges can be effectively used by endo-functionalized macrocyclic hosts for molecular recognition in water, where solvent screening on polar noncovalent interactions is high.

2.
Chemphyschem ; 21(20): 2249-2253, 2020 10 16.
Artigo em Inglês | MEDLINE | ID: mdl-32869462

RESUMO

The thermodynamically unstable, colourless closed-ring isomer of spiropyran can be stabilized in water by the anti-configurational isomer of amide naphthotube. The influence of the binding on the thermodynamics and kinetics of spiropyran have been studied. The complex was further used to prepare a test paper that allows naked-eye detection of toxic paraoxon.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32902085

RESUMO

Optical chirality sensing has attracted a lot of interest due to its potential in high-throughput screening in chirality analysis. A molecular sensor is required to convert the chirality of analytes into optical signals. Although many molecular sensors have been reported, sensors with wide substrate scope remain to be developed. Herein, we report that the amide naphthotube-based chirality sensors have an unprecedented wide scope for chiroptical sensing of organic molecules. The substrates include, but are not limited to common organic products in asymmetric catalysis, chiral molecules with inert groups or remote functional groups from their chiral centers, natural products and their derivatives, and chiral drugs. The effective chirality sensing is based on biomimetic recognition in water and on effective chirality transfer through guest-induced formation of a chiral conformation of the sensors. Furthermore, the sensors can be used in real-time monitoring on reaction kinetics in water and in determining absolute configurations and ee values of the products in asymmetric catalysis.

4.
Angew Chem Int Ed Engl ; 59(45): 19945-19950, 2020 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-32696557

RESUMO

Benzene hydrogenation is an important industrial process. The reaction is incomplete, resulting in a mixture of benzene, cyclohexane, and/or cyclohexene that have to be separated before any further reactions. The currently used extractive and azeotropic distillations are operationally complex and energy intensive. Adsorptive separation provides an alternative energy-efficient method. However, the separation of the ternary mixture by adsorptive separation has not yet been reported. In the present research, we report two macrocyclic hosts with hydrogen-bonding sites in their cavities that are able to separate the ternary mixture of benzene, cyclohexene, and cyclohexane. N-H⋅⋅⋅π interactions were found to play a key role in the selective separation. In addition, fast adsorption, high loading ratios, and easy recycling are achieved with the present system, which is promising for practical applications.

5.
Nat Commun ; 11(1): 2740, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32488094

RESUMO

Induced fit and conformational selection are two dominant binding mechanisms in biology. Although induced fit has been widely accepted by supramolecular chemists, conformational selection is rarely studied with synthetic systems. In the present research, we report a macrocyclic host whose binding mechanism is unambiguously assigned to conformational selection. The kinetic and thermodynamic aspects of this system are studied in great detail. It reveals that the kinetic equation commonly used for conformational selection is strictly followed here. In addition, two mathematical models are developed to determine the association constants of the same guest to the two host conformations. A "conformational selectivity factor" is defined to quantify the fidelity of conformational selection. Many details about the kinetic and thermodynamic aspects of conformational selection are revealed by this synthetic system. The conclusion and the mathematical models reported here should be helpful in understanding complex molecular recognition in both biological and synthetic systems.


Assuntos
Fenômenos Biofísicos , Domínios Proteicos , Proteínas/metabolismo , Compostos Heterocíclicos/química , Compostos Heterocíclicos/metabolismo , Cinética , Ligantes , Modelos Moleculares , Modelos Teóricos , Ligação Proteica , Conformação Proteica , Proteínas/química , Termodinâmica
6.
Org Biomol Chem ; 18(10): 1900-1909, 2020 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-32108203

RESUMO

Amide naphthotubes with four carboxylate sidechains have been reported by us for selectively recognizing hydrophilic molecules in water and they have found applications in sensing and self-assembly. Modification of these macrocycles on the sidechains would further expand their applicability. Herein, we report the synthesis of mono-functionalized amide naphthotubes with one alkyne and three carboxylate groups. These naphthotubes show rather different binding affinities from that of the amide naphthotubes with four carboxylate sidechains. The partial self-inclusion of the alkyne group in the cavity was invoked to explain these differences. In addition, the syn- and anti-configurational isomers of the naphthotubes with four carboxylate groups were found to be assigned incorrectly in our earlier publication. Further evidence is provided here for the new assignment. The implications of this new structural assignment for the conclusions drawn in the earlier works are discussed as well.

7.
Chem Commun (Camb) ; 56(6): 888-891, 2020 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-31858093

RESUMO

A 2,3-dialkoxynaphthalene-based naphthocage has been synthesized. This naphthocage prefers to bind small organic cations with its low-symmetry conformation, which is in contrast to 2,6-dialkoxynaphthalene-based naphthocages. Self-sorting of these two naphthocages with two structurally similar guests tetramethylammonium and tetraethylammonium was achieved as well.

8.
Chem Commun (Camb) ; 55(73): 10924-10927, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31441488

RESUMO

Two positively-charged naphthotubes with imidazolium as the bridges were synthesized and their structures have been characterized by 1H NMR, MS, and X-ray crystallography. These naphthotubes are capable of binding aromatic hydrocarbons. Surprisingly, the binding affinities are much higher in CD3CN than in CD2Cl2. The solvent effect on the ion pairing interactions and competitive binding of CD2Cl2 was invoked to explain this unusual phenomenon.

9.
Chem Commun (Camb) ; 54(74): 10394-10404, 2018 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-30066702

RESUMO

The last two decades have witnessed the development of metal-catalyzed asymmetric additions of arylboronic acids to electron-deficient double bonds. Much research has been directed towards Rh(i)-catalysis because of the high activity of this transition metal for these types of reactions. Recently, significant advances have emerged in Pd(ii), Ni(ii), and Co(ii)-catalyzed asymmetric additions of organoboron reagents. This feature article highlights the development of additions to ketimines catalyzed by these three metals, that is, (i) Pd(ii)-catalyzed enantioselective additions of arylboronic acids to ketimines, (ii) Ni(ii)-catalyzed enantioselective additions of arylboronic and alkenylboronic acids to ketimines, and (iii) Co(ii)-catalyzed enantioselective additions of potassium allyltrifluoroborate to ketimines.

10.
Nat Commun ; 9(1): 2258, 2018 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-29884893

RESUMO

Chiral allylic amines are not only present in many bioactive compounds, but can also be readily transformed to other chiral amines. Therefore, the asymmetric synthesis of chiral allylic amines is highly desired. Herein, we report two types of Ni(II)-catalyzed asymmetric alkenylation of cyclic ketimines for the preparation of chiral allylic amines. When ketimines bear alkyl or alkoxycarbonyl groups, the alkenylation gives five- and six-membered cyclic α-tertiary allylic amine products with excellent yields and enantioselectivities under mild reaction conditions. A variety of ketimines can be used and the method tolerates some variation in alkenylboronic acid scope. Furthermore, with alkenyl five-membered ketimine substrates, an alkenylation/rearrangement reaction occurs, providing seven-membered chiral sulfamide products bearing a conjugated diene skeleton with excellent yields and enantioselectivities. Mechanistic studies reveal that the ring expansion step is a stereospecific site-selective process, which can be catalyzed by acid (Lewis acid or Brønsted acid).

11.
Chem Commun (Camb) ; 53(3): 609-612, 2017 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-27981326

RESUMO

A Ni(ii)-catalyzed asymmetric addition of arylboronic acids to cyclic aldimines and ketimines is reported. Our tropos phosphine-oxazoline biphenyl ligand is crucial for the high catalytic activity, which coordinates to Ni(ii) to form a complex with a single axial configuration. The desired chiral amine products could be prepared with excellent yields (up to 99%) and enantioselectivities (up to 99.8%) under mild reaction conditions.

12.
Org Lett ; 17(9): 2250-3, 2015 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-25879921

RESUMO

A palladium-catalyzed asymmetric addition of arylboronic acids to nitrostyrene is reported. The catalytic system employing iPr-IsoQuinox as a chiral ligand in MeOH solvent under an air atmosphere provides the chiral diarylsubstituted products in high yields with good enantioselectivities. A variety of functionalized nitrostyrenes can be used, and the method tolerates some variation in arylboronic acid scope. The stereochemical outcome can be explained using a stereochemical model.

13.
Org Lett ; 16(6): 1570-3, 2014 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-24621181

RESUMO

C-O bond cleavage of allylic alkyl ether was realized in a Pd-catalyzed hydrogen-bond-activated allylic alkylation using only alcohol solvents. This procedure does not require any additives and proceeds with high regioselectivity. The applicability of this transformation to a variety of functionalized allylic ether substrates was also investigated. Furthermore, this methodology can be easily extended to the asymmetric synthesis of enantiopure products (99% ee).


Assuntos
Compostos Alílicos/síntese química , Éteres/química , Paládio/química , Álcoois/química , Alquilação , Compostos Alílicos/química , Catálise , Técnicas de Química Combinatória , Ligação de Hidrogênio , Estrutura Molecular , Estereoisomerismo
14.
Org Biomol Chem ; 11(42): 7412-9, 2013 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-24077558

RESUMO

Chiral ß-aryl-α,ß-unsaturated amino alcohols were synthesized via a Pd-catalyzed asymmetric allylic amination of 4-aryl-1,3-dioxolan-2-one using planar chiral 1,2-disubstituted ferrocene-based phosphinooxazolines as ligands. Under the optimized reaction conditions, a series of substrates were examined and the products were obtained in good to excellent yields (up to 92%) and enantioselectivities (up to 98% ee) under mild reaction conditions. The desired products were determined to be of (R)-configuration and could subsequently be transformed into compounds with interesting biological activity using simple transformations.


Assuntos
Alcenos/química , Amino Álcoois/química , Amino Álcoois/síntese química , Paládio/química , Aminação , Catálise , Técnicas de Química Sintética , Compostos Ferrosos/química , Ligantes , Metalocenos , Oxazóis/química , Estereoisomerismo , Especificidade por Substrato
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