• Journal of the Korean Chemical Society
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• v.34 no.4
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• pp.345-351
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• 1990

Optical isomers of DABS-amino acids have been separated in a reversed phae high performance liquid chromatography by adding Cu (Ⅱ)-L-Proline chelate to the mobile phase. The retention behaviors for the DABS-amino acids are discussed in terms of pH of the mobile phase and the concentrations of acetonitrile, Cu (Ⅱ) complex, and buffer. The selectivity of the optical isomers of DABS-amino acids increases with the pH of the mobile, and the concentration of the chelate, but decreases with concentration of the oganic modifier. The concentration of buffer does not affect the optical separation selectivity. A separation mechanism is illustrated by cis and trans formation based on the steric effect of the ligand exchange reaction between DABS-amino acids and the copper chelate.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.207-212
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• 2001

DFT calculations have been performed on several substituted 1,4-diaza-1,3-butadienes (1,4-DABs) with electron donating and withdrawing groups at the terminal two nitrogens to investigate the reactivity of Diels-Alder reaction with acrolein. The calculated FMO (Frontier Molecular Orbital) energies for the optimized 1,4-disubstituted-1,4-DABs have been used to explain both normal and inverse electron demand Diels-Alder reactions. It is shown that the electron donating and withdrawing substituents lead to the normal(HOMO diene controlled) and inverse electron demand (LUMO diene controlled) Diels-Alder reactions, respectively.

• Journal of Information Technology Services
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• v.22 no.4
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• pp.81-95
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• 2023

The emergence of Security Token has revolutionized the way assets are traded, bringing efficiency, transparency, and accessibility to the market. However, the Real Estate Security Token market faces challenges, particularly in terms of liquidity. The CMTO(Collateralized Mortgage Token Obligation) model addresses this issue by introducing a novel approach that combines the benefits of NFT(Non-Fungible Token), STO(Security Token Offering), and CMO(Collateralized Mortgage Obligation) techniques to enhance liquidity and promote investment in Real Estate Security Token. The CMTO framework functions by allowing DABS token investors to leverage their tokens as collateral for loans. These token-collateralized loans are pooled together and form the basis for issuing Sequential CMO named CMTO. The CMTO represent a diversified portfolio of token-collateralized loans, providing investors with options based on their financial goals and risk preferences. By implementing CMTO, the Real Estate Security Token market can overcome liquidity challenges, attract a broader range of investors, and unlock the full potential of digital assets in the real estate industry.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.879-888
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• 1992

Separation of the optical isomers of free amino acids by a reversed phase high performance liquid chromatography has been studied by adding a copper(II) complex of L-proline or L-proline derivatives (hydroxy-L-proline, N-benzyl-L-proline, p-xylenyl-L-proline, p-xylenyl-hydroxy-L-proline) in the mobile phase. An OPA postcolumn detection system was used for the detection of amino acids. The chromatographic properties for the free amino acids were discussed in terms of the pH, the kinds and concentration of chelate or organic modifier. The retention behaviors of the free amino acids were considerably different from, those of DNS-amino acids or DABS-amino acids. The enantioselectivity of the free amino acids was better than that of derivatized amino acids. The enantioselectivity between the optical isomers observed by use of the Cu(II)-p-xylenyl-L-proline chiral cheleate was the best among the several copper(II) chelate. A separation mechanism could be illustrated not only by the hydrophobic interaction of the diastereomer with stationary phase but also by the steric effect of the ligand exchange reaction between the free-amino acids and copper chelate.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.131-135
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• 2015

Two new bitter-tasting cyclic peptides comprising six amino acids, namely gamakamide C and D, were isolated from cultured oysters Crassostrea gigas. Dimethylaminoazobenzene sulfonyl-amino acid analysis detected Val and Leu in gamakamide C and Ile and Leu in gamakamide D. The molecular formula of gamakamide C was determined as $C_{43}H_{60}N_{7}O_8S$ by high-resolution fast atom bombardment mass spectroscopy (HR FAB-MS) ($[M+H]^+m/z822.4200{\Delta}-2.4mmu$), and that of gamakamide D was determined as $C_{43}H_{62}N_7O_8S$ by HR FAB-MS ($[M+H]^+m/z836.4379{\Delta}-2.0mmu$). Comparison of amino acid analyses and fragment ions by MS/MS among gamakamide C, D, and E (known), the structures of gamakamide C and D were confirmed $as-{\small{L}}-Val-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$ and $-{\small{L}}-Ile-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$, respectively.