• 폴리머
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• 제30권4호
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• pp.357-361
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• 2006

생체 내에서 생성되는 알파 리포산은 산화방지, 혈당량 조절뿐만 아니라 식욕 억제, 비만 억제 효과 등을 가지고 있다. 약물로도 이용되고 있는 이 물질은 두 개의 황을 함유하고 있는 오각형 고리구조를 가지고 있어, 열과 자외선에 의해서 쉽게 개환되고 나아가 고분자로 중합될 수 있어서 약물로서 투여했을 경우 생체 이용률이 낮아지는 문제가 보고되어 있다. 본 연구는 개환에 따른 고분자화를 위한 다양한 조건을 조사하였다. 리포산은 녹는점이 지나야만 개환이 발생하였지만 그 이상의 온도에서는 온도의존성이 없었다. $70^{\circ}C$에서 개환율은 시간에 비례하였고 농도에 반비례하였다. 1시간 동안, $70^{\circ}C$ 아세트산에서 자외선과 함께 개환된 경우 개환율은 가장 높은 70% 였다. 이렇게 개환된 알파 리포산들은 대부분이 이황 고분자로 변했고, 개환율이 커질수록 고분자의 분자량 도 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제26권9호
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• pp.1339-1343
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• 2005

The N-inversion energies and nucleophilic ring-opening reactions of N-substituted aziridine compounds are investigated using B3LYP/6-31+$G^*$ methods, where substituents (R) on the nitrogen atom has been H (1), Me (2), Ph (3), Bn (4), CHMePh (5), $CO_2Me$ (6), COPh (7) and $SO_2Ph$ (8). The N-inversion energy with X group are decreased as the following order: R = CHMePh (17.06 kcal/mol) $\gt$ Me (16.97) $\gt$ Bn (16.70) $\gt$ H (16.64) $\gt$ $SO_2Ph$ (12.18) $\gt$ Ph (8.91) $\gt$ COPh (5.75) $\gt$ $CO_2Me$ (5.48). For reactivity of the ring opening toward cyanide ion, the aziridine 6 (R=$CO_2Me$) is shown to be the most reactive one. During the ring opening of aziridine 6 by CN$^{\ominus}$, the torsional OCNC angle becomes near to $180^{\circ}$, where the geometry allows for the effective incorporation of electrons of the nitrogen atom to the C=O bond. It would be a possible driving force for nucleophilic ring opening reaction as well as decreasing the N-inversion energy barrier. Regarding to the regioselectivity, the orientation of nucleophile in ring opening reaction appears to be different in the case of 9 and 10. The results are discussed in terms of steric/electronic effect of the $C_2$-substituents.

• Bulletin of the Korean Chemical Society
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• 제29권2호
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• pp.313-318
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• 2008

An enantioselective ring opening of racemic terminal epoxides has been achieved by using heterobimetallic cobalt salen complexes with variety of nucleophiles. They were proven to be highly enantioselective and reactive for the synthesis of valuable chiral building blocks in enantio-riched forms up to 98% ee.

• 통합자연과학논문집
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• 제5권2호
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• pp.91-99
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• 2012

A newly-devised Meerwein-Ponndorf-Verley (MPV) reagents, such as diisobutylacetoxyalanes and diisobutylmethanesulfonylalanes, achieved a clean conversion of unsymmetrical epoxides to the corresponding less substituted alcohols. This review covers the recent developments for such a regiospecific ring-opening reaction of epoxides.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2286-2290
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• 2013

Ring opening reactions of epoxides with oxygen nucleophiles catalyzed by a variety of quaternary onium salt, such as ammonium or phosphonium salt were explored. The results showed that tetrabutylphosphonium bromide (TBPB) among salts serves as the most efficient catalyst for this process and that expoxide ring opening reactions with a variety of oxygen nucleophiles including carboxyic acid and phenol, promoted using this salt, lead to generate readily purifiable products in excellent yields.

• Archives of Pharmacal Research
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• 제8권4호
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• pp.221-227
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• 1985

Acetyl-11-ketopomolic acid methyl ester (VI), mp 276-$278^{\circ}$ was synthesized from pomolic acid (III). The mild alkaline treatment of VI induced the opening of ring E on carbone skeleton to yield VII, and then VII was deacetylated to give VIII, mp 82-$84^{\circ}$ Compound VIII was established as 11, 19-diketo-18, 19-secoursolic acid methylester. The E-ring opening was believed to be due to regrograde aidol condensation.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.43-46
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• 2005

Reaction energies were determined for reductive ring-opening reactions of Li$^+$-coordinated ethylene carbonate (EC) and vinylene carbonate (VC) by a density functional method. We have also explored the ring-opening of Li$^+$-EC and Li$^+$-VC by reaction with a nucleophile (CH$_3$O$^-$.) thermodynamically. Our thermodynamic calculations led us to conclude that the possible reaction products are CH$_3$OCH$_2$CH$_2$OCO$_2$Li (O$_2$-C$_3$ cleavage) for Li$^+$-EC +CH$_3$O$^-$., and CH$_3$OCHCHOCO$_2$Li (O$_2$-C$_3$ cleavage) and CH$_3$OCO$_2$CHCHOLi (C$_1$-O$_2$ cleavage) for Li$^+$-VC +CH$_3$O$^-$.. The opening of VC would occur at the C$_1$-O$_2$ side by a kinetic reason, although the opening at the O$_2$-C$_3$ side is more favorable thermodynamically.

• Bulletin of the Korean Chemical Society
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• 제27권9호
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• pp.1283-1284
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• 2006

• Bulletin of the Korean Chemical Society
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• 제35권3호
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• pp.695-696
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• 2014

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3431-3433
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• 2010