chirality of sandwich type of organic molecules has been discovered. The key element of this chirality is characterized by three layers of structures that are arranged nearly in parallel fashion with ...one on top and one down from the center plane. Individual enantiomers of these molecules have been fully characterized by spectroscopies with their enantiomeric purity measured by chiral HPLC. The absolute configuration was unambiguously assigned by X-ray diffraction analysis. This is the first multilayer
chirality reported and is anticipated to lead to a new research area of asymmetric synthesis and catalysis and to have a broad impact on chemical, medicinal, and material sciences in future.
A novel class of polymers and oligomers of chiral folding chirality has been designed and synthesized, showing structurally compacted triple-column/multiple-layer frameworks. Both uniformed and ...differentiated aromatic chromophoric units were successfully constructed between naphthyl piers of this framework. Screening monomers, catalysts, and catalytic systems led to the success of asymmetric catalytic Suzuki-Miyaura polycouplings. Enantio- and diastereochemistry were unambiguously determined by X-ray structural analysis and concurrently by comparison with a similar asymmetric induction by the same catalyst in the asymmetric synthesis of a chiral three-layered product. The resulting chiral polymers exhibit intense fluorescence activity in a solid form and solution under specific wavelength irradiation.
So far, there have been 4 methods to control chirality including the use of chiral auxiliaries, reagents, solvents, and catalysts documented in literature and textbooks. Among them, asymmetric ...catalysts are normally divided into homogeneous and heterogeneous catalysis. In this report, we present a new type of asymmetric control-asymmetric catalysis via chiral aggregates that would not belong to the above categories. This new strategy is represented by catalytic asymmetric dihydroxylation reaction of olefins in which chiral ligands are aggregated by taking advantage of typical aggregation-induced emission systems containing tetrahydrofuran and H
O cosolvents. It was proven that the chiral induction can be enhanced from er of 78:22 to 97:3 simply by changing the ratios of these 2 cosolvents. The formation of chiral aggregates of asymmetric dihydroxylation ligands, (DHQD)
PHAL and (DHQ)
PHAL, has been proven by aggregation-induced emission and a new analytical tool-aggregation-induced polarization established by our laboratory. In the meanwhile, chiral aggregates were found to be formed either by adding NaCl into tetrahydrofuran/H
O systems or by increasing concentrations of chiral ligands. The present strategy also showed promising reverse control of enantioselectivity in the Diels-Alder reaction. This work is anticipated to be extended broadly to general catalysis, especially to asymmetric catalysis in the future.
Little is known about the optimal time to consume caffeine prior to exercise to maximize the ergogenic benefits of the substance.
To determine the optimal pre-exercise time interval to consume ...caffeine to improve lower-body muscular performance. A secondary aim was to identify the presence of any sex differences in responses to timed caffeine administration.
Healthy, resistance-trained males (
= 18; Mean±SD; Age: 25.1 ± 5.7 years; Height: 178.4 ± 7.1 cm; Body mass: 91.3 ± 13.5 kg; Percent body fat: 20.7 ± 5.2; Average caffeine consumption: 146.6 ± 100.3 mg/day) and females (
= 11; Mean ± SD; Age: 20.1 ± 1.6 years; Height: 165.0 ± 8.8 cm; Body mass: 65.8 ± 10.0 kg; Percent bodyfat: 25.8 ± 4.2; Average caffeine consumption: 111.8 ± 91.7 mg/day) participated in this investigation. In a randomized, double-blind, placebo-controlled, crossover fashion, participants consumed 6 mg·kg
caffeine or placebo solution at three time points: 2 h prior (2H), 1 h prior (1H), or 30 min prior (30M) to exercise testing. During three visits, caffeine was randomly administered at one time point, and placebo was administered at the other two time points. During one visit, placebo was administered at all three time points. Next, participants performed isometric mid-thigh pulls (IMTP), countermovement vertical jumps (CMVJ), and isometric/isokinetic knee extensor testing (ISO/ISOK).
Caffeine administered at 1H significantly improved absolute CMVJ and ISO performance relative to placebo. Mean CMVJ jump height was significantly higher during 1H compared to 30M. However, only caffeine administered at 30M significantly improved absolute measures of isokinetic performance. Analysis of the pooled caffeine conditions revealed that muscular performance was more consistently augmented by caffeine in males compared to females.
Pre-exercise caffeine timing significantly modulated participant responses to the substance, with 1H exerting the most consistent ergogenic benefits relative to other time points, particularly compared to 2H. Male participants were found to respond more consistently to caffeine compared to female participants. These results suggest that active individuals can maximize the ergogenic effects of caffeine by consuming the substance ~1 h prior to the point when peak muscular performance is desired.
Two series of di-ionizable calix4arene-1,2-crown-5 and -crown-6 ethers in cone conformations are synthesized. The ionizable groups are oxyacetic acid moieties and
N-(X)sulfonyl oxyacetamide units ...with X=methyl, phenyl, 4-nitrophenyl, and trifluoromethyl, which ‘tunes’ their acidity. For competitive solvent extraction of alkaline earth metal cations from aqueous solutions into chloroform, the new ligands with
N-(X)sulfonyl carbamoyl groups are efficient extractants with Ba
2+ selectivity. On the other hand, the dicarboxylic acid analogues exhibit little selectivity in extraction of alkaline earth metal cations. For single species extractions of Pb
2+, the ligands with both types of ionizable groups show very good extractions abilities. In single species extractions of Hg
2+, the
N-(X)sulfonyl carboxamide ligands are highly efficient, in contrast to the dicarboxylic acid compounds. Influences of the ionizable group identity, the crown ether ring size, and the presence of upper-rim
p-
tert-butyl groups on divalent metal ion extraction are explored.
Di-ionizable calix4arene-1,2-crown-5 and -crown-6 ethers in the cone conformation exhibit selectivity for Ba
2+ in competitive solvent extraction of alkaline earth metal cations and high extraction ability for Pb
2+ and for Hg
2+ in single species extraction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The influence of Li
+, Na
+, K
+, Rb
+, Cs
+, Mg
2+, Ca
2+, Sr
2+, Ba
2+, Ag
+, Cd
2+, Co
2+, Fe
2+, Hg
2+, Mn
2+, Pb
2+, Zn
2+ and Fe
3+ on the spectroscopic properties of two dansyl ...(1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims of a series of three, structurally related, di-ionized calix4arenes is investigated by means of absorption and emission spectrophotometry. Di(tetramethylammonium) salts of the di-ionized ligands,
L,
L1, and
L2, which differ in having no, two and four allyl groups, respectively, on the upper rim of the calix4arene scaffold, are utilized for the spectrofluorimetric titration experiments in MeCN. On complexation by alkaline earth metal cations, the emission spectra undergo marked red shifts and quenching of the dansyl fluorescence. These effects are weaker with alkali metal cations. Transition metal cations and Pb
2+ interact strongly with the ligands. In particular, Fe
3+, Hg
2+ and Pb
2+ cause greater than 99% quenching of the dansyl fluorescence.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Two 8,8′ disubstituted binaphthyl ligands have been designed and synthesized in 3.1% and 11.4% overall yield, respectively. X-ray structure analysis demonstrated that a unique chiral microenvironment ...was created. With the assistance of a new aggregation-induced polarization (AIP) technology, chiral aggregates were determined as the fraction of polar solvent increased in the nonpolar/polar solvent system, which indicated their potential in modern asymmetric synthesis and catalysis.
A new chiral phosphine ligand and its diol derivative have been designed and synthesized asymmetrically.
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IJS, KILJ, NUK, UL, UM, UPUK
In this work, we present a strategy for the preparation of functionalized 2,3-dihydrobenzofuran derivatives
via
the Cs
2
CO
3
-catalyzed domino annulation of enantiopure chiral salicyl
N
-phosphonyl ...imines with bromo malonates, which offers an avenue for the construction of 2,3-dihydrobenzofurans. Nineteen examples were synthesized in impressive chemical yields and diastereoselectivity. The products were purified simply by washing the crude mixtures with hexanes following group-assisted purification chemistry/technology to bypass traditional separation methods which often result in a loss of product. The absolute configuration was unambiguously assigned by X-ray structural analysis.
A new asymmetric method for the synthesis of highly functionalized 2,3-dihydrobenzofuranes in good to high yields and excellent diastereoselectivity
via
group-assisted purification (GAP) chemistry.
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.
The first asymmetric catalytic approach to multilayer 3D chirality by using Suzuki‐Miyaura cross‐couplings in the presence of new chiral amide‐phosphines is reported. The resulting multilayer products showed strong luminescence under UV irradiation, and displayed strong aggregation‐induced emission (AIE).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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