• Current Optics and Photonics
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• 제3권4호
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• pp.275-284
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• 2019

Chirality is ubiquitous in physics and biology from microscopic to macroscopic phenomena, such as fermionic interactions and DNA duplication. In photonics, chirality has traditionally represented differentiated optical responses for right and left circular polarizations. This definition of optical chirality in the polarization domain includes handedness-dependent phase velocities or optical absorption inside chiral media, which enable polarimetry for measuring the material concentration and circular dichroism spectroscopy for sensing biological or chemical enantiomers. Recently, the emerging field of non-Hermitian photonics, which explores exotic phenomena in gain or loss media, has provided a new viewpoint on chirality in photonics that is not restricted to the traditional polarization domain but is extended to other physical quantities such as the orbital angular momentum, propagation direction, and system parameter space. Here, we introduce recent milestones in chiral light-matter interactions in non-Hermitian photonics and show an enhanced degree of design freedom in photonic devices for spin and orbital angular momenta, directionality, and asymmetric modal conversion.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1715-1718
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• 2012

2-Hydroxy-6-(1-(3-phenylurylphenyl)ethoxy)-benzaldehyde ($\mathbf{2}$) has been synthesized in racemic form from 1,3-Dihydroxybenzene via formylation and reaction with 3-phenyluryl-methylbenzylbromide. The optically pure form of $\mathbf{2}$ was separated by normal silica column chromatography from the imine diastreomer which was obtained by the reaction of racemic mixture of $\mathbf{2}$ with optically pure leucinol. The absolute configuration of the separated enantiomer of $\mathbf{2}$ was decided from the energy calculation of the corresponding imine diastereomers. The activity of $\mathbf{2}$ as a chirality conversion reagent (CCR) for amino acids was determined by $^1H$ NMR analysis. The efficiency of $\mathbf{2}$ is not better than the previous CCRs based on binaththol. Compound $\mathbf{2}$, however, has lower molecular weight compared to other CCRs. This work demonstrates that asymmetric carbon can control the selectivity of amino acids.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1263-1267
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• 2011

Novel binol-based uryl and guanidinium receptors having higher ring conjugation at the periphery of the hydrogen bonding donor sites have been synthesized and utilized to study the enantioselective recognition of 1,2-aminoalcohols and chirality conversion of natural amino acids via imine bond formation. There is a remarkable decrease in the stereoselectivites as the conjugation increases at the periphery of hydrogen bonding donor sites. The guanidinium-based receptors show more selectivity towards the amino alcohol than that of the uryl based ones due to its charge reinforced hydrogen bonds. The conversion efficiency of L-amino acids to Damino acids by the uryl-based receptors is higher than that of the guanidinium-based ones.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.409-414
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• 2009

Novel binol aldehydes derivatized at 2' hydroxy position with both uryl and acetamide groups (2), and diuryl groups (3) have been synthesized. Both were designed for streospecific binding and chirality conversion of general dipeptides with support of multiple hydrogen bonding donor sites in the receptors. The receptors, 2 and 3, converted the chirality of N-terminal amino acids of peptides such as Ala-Gly, Met-Gly, Leu-Gly and His-Gly with stereoselectivity on D-form over L-form. The stereoselectivity ratios were in the range of 5-11, somewhat higher than those of the binol receptor with mono uryl group (1). The DFT calculation at the B3LYP/6-31G$^*$//MPWB1K/6-31G$^*$ level revealed that 3-D-Ala-Gly was 2.2 kcal/mol more stable than 3-L-Ala-Gly. The considerable steric hindrance between the methyl group of the alanine and the imine CH moiety of the receptor seems to be the main contributing factor for the thermodynamic preference.

• Bulletin of the Korean Chemical Society
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• 제30권12호
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• pp.2938-2942
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• 2009

New receptors 1-3 that bind stereoselectively amino alcohols and convert chirality of amino acidsvia imine bond formation were synthesized. The receptors have uryl (1), thiouryl (2) and guanidinium (3) groups all with additional phenylcarbonyl motifs, which are effective hydrogen bonding donors and play a key role in the stereoselective recognitions. The stereoselectivities were measured from the integration of $^1HNMR$ peaks. Compound 1 and 2 showed the stereoselectivities for the imine formation with amino alcohols ($K_R/K_S$) in the range of 2${\sim}$4, and compound 3 in the range of 4${\sim}$8. Chirality conversion efficienciesof 1-3 for amino acids, i.e. D/L ratio at equilibrium, are in the range of 1.5${\sim}$5.6, showing a little higher efficiency with 3. The additional phenylcarbonyl motifs in 1-3 were revealed not to contribute to significant enhancement of the selectivities.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1289-1294
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• 2010

Novel $H_8$-binaphthol-based chiral receptors appended with an uryl moiety (2a) and a guanidinium moiety (2b) have been designed and synthesized for the enantioselective recognition of 1,2-amino alcohols via reversible imine formation. The selectivities ($K_R/K_S$ = 9.8 ~ 19.4) of 2b in imine formation with 1,2-amino alcohols are higher than those of 2a ($K_R/K_S$ = 1.8 ~ 4.5). Similar efficiency trend have been observed in the conversion of L-amino acids to D-amino acids, i.e., the efficiency of the receptor 2b (D/L ratio: 4.3 ~ 10.1) is superior to 2a (D/L ratio: 4.0 ~ 8.7).