• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.165-171
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• 2017

Diels-Alder 반응은 고리형 탄소화합물을 만드는 유기 합성 과정에서 매우 중요한 반응이다. 이 반응은 중간생성물 없이 오직 1 step으로 진행되는데, diene이나 dienophile에 결합한 치환기의 electron donating 및 electron withdrawing 성질에 따라 반응성이 달라진다고 알려져 있다. 이 때 반응물인 diene과 dienophile의 분자 오비탈 및 전이 상태의 에너지 변화를 계산화학을 통해 분석한다면 Diels-Alder 반응을 보다 심도 있게 이해할 수 있다. 이에 따라 본 연구에서는 DFT 계산을 통하여 치환기에 따른 활성화 에너지의 크기와 diene의 nucleophilicity 및 dienophile의 electrophilicity를 비교하였다. 이를 통해 electron withdrawing group의 경우 분자의 electrophilicity를 증가시키고, electron donating group의 경우 nucleophilicity를 증가시킨다는 것을 확인할 수 있었다. 그 결과, Diels-Alder 반응이 일어날 때 dienophile의 경우 치환된 electron withdrawing group에 의해 electrophilicity가 증가함에 따라 활성화 에너지가 낮아져 반응이 잘 일어나고, 반대로 diene의 경우 electron donating group이 치환되어 있을 때 nucleophilicity의 증가에 따라 반응이 잘 일어난다는 것을 알 수 있었다.

• Archives of Pharmacal Research
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• v.23 no.2
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• pp.151-154
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• 2000

Two sesquiterpene endoperoxides, 1S, 4R, 6R-1, 4-endoperoxy-bisabola-2, 10-diene (1), 1R, 4S, 6R-1, 4-endoperoxy-bisabola-2, 10-diene (II), and a sesquiterpene hydroperoxide, 1$\beta$-hydroperoxygermacra-4 (15), 5, 10 (14)-triene (III) were isolated from the aerial parts of Artemisia stolonifera (Compositae). Their chemical structures were assigned by spectral evidences. Compounds I and II exhibited cytotoxicity against five human tumor cell lines with their $\ED_50 values ranging from 0.20 to 5.43 ${\mu}g/m\ell$ and from <0.1 to 0.87 ${\mu}g/m\ell$, respectively.

• Journal of the Korean Chemical Society
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• v.30 no.6
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• pp.521-525
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• 1986

From the reaction of phenyltrimethylsilylacetylene with lithium, 1,4-bis(trimethylsilyl)-2,3-diphenyl-1,4-butadene dianion was formed. The reaction of dianion with dichlorodimethylsilane affords 1,1-dimethyl-2,5-bis(trimethylsilyl)-3,4-diphenyl-1-silacyclopenta-2,4-diene. In addition 1,4-bis(trimethylsilyl)-2,3-diphenyl-1,3-butadiene was isolated. It seems to be hydrolized product in alkali medium.

• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.849-853
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• 1996

Hetero Dieis-Alder reactions containing phosphorus atom at various positions of diene and dienophile as well as standard Dieis-Alder reaction between ethylene and cis-l,3-butadiene have been studied using ab initio method. Activation energy showed a good linear relationship with the FMO energy gap between diene and dienophile, which can be normally used to explain Dieis-Alder reactivity. Since π-bond cleavage and σ-bonds formation occur concertedly at the TS, geometrical distortion of diene and dienophile from the reactant to the transition state is the source of barrier. Based on the linear correlations between activation barrier and deformation energy, and between deformation energy and π-bond order change, it was concluded that the activation barrier arises mainly from the breakage of π-bonds in diene and dienophile. Stabilization due to favorable orbital interaction is relatively small. The geometrical distortions raise MO levels of the TS, which is the origin of the activation energy. The lower barrier for the reactions of phosphorus containing dienophile (reactions C, D, and E) can be explained by the electronegativity effect of the phosphorus atom.

• Bulletin of the Korean Chemical Society
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• v.8 no.4
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• pp.270-272
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• 1987

1,1-Dichloro-2,3,4,5-tetraphenyl-1-silacyclopenta- 2,4-diene was synthesized through the reaction of $SiCl_4$ with 1,4-dilithiotetraphenylbutadiene in 50% yield. From the reaction of this silole with metal, an air sensitive red-brownish solid was obtained. Treatment of this reaction product with $CH_3I\; and\; Me_3SiCl$ gave 1,1-dimethyl-2,3,4,5-tetraphenyl-1-silacyclopenta- 2,4-diene and 1,1-bis(trimethylsilyl)-2,3,4,5-tetraphenyl-1-silacyclopenta-2,4-diene, respectively. From these results, the formation of reactive 2,3,4,5-tetraphenyl-1-silacyclopenta-2,4-dienyl dianion was confirmed.

• Korean Journal of Plant Resources
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• v.4 no.2
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• pp.35-38
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• 1991

Two new diterpene compounds have been isolate from the roots of Eragrostis ferruginea (Thunb.) Beauv. and their structures were elucidated as isopimara-9(11), 15-0ien-l9-ol-3-one and cassa-13(14), 15-diene-3, 12-dione by various spectroscopic me-thods. We have also isolated a known diterpene diol isopimara-9(11). 15-diene-3$\beta$, 19-dio1.

• Journal of the Korean Chemical Society
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• v.37 no.7
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• pp.648-654
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• 1993

$[M(cyclam)X_2]Y(M=Co^{3+},\;Fe^{3+},\;Mn^{3+}\;:\;X=Cl-^,\;Br^-,\;NCS^-\;:\;Y=Cl^-,\;Br^-,\;NCS^-),\;[Co(trans-14-diene)X_2]Y(X=Cl^-,\;Br^-\;:\;Y=ClO_4^-)\;and\;[Co(trans-14-diene)](ClO_4)_2$ were able to activate an molecular oxygen under sodium borohydride. 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol reacted with activated molecular oxygen to give 2,4-tert-butyl-1,6-benzoquinone(BQ) and 3,5,3',5'-tetra-tert-butyldiphenoquinone(DPQ). The saturated tetraazamacrocyclic complexes, $[Co(cyclam)X_2]Y$, were more an effective catalyst than $[Co(trans-14-diene)X_2]Y$ the unsaturated complexes in the formation of BQ and DPQ. The mole ratio of $O_2$ vs. catalyst $(O_2/M)$ for $[Co(cyclam)X_2]Y$ and [Co(trans-14-diene)X_2]Y$ was 1/1, while it was 1/2 for $[M(cyclam)Cl_2]Cl(M=Fe(III),\;Mn(III))$. The results suggested that Co(III)-macrocyclic complexes activated molecular oxygen as superoxolike ${O_2}^-$ and $[M(cyclam)Cl_2]Cl(M=Fe(III),\;Mn(III))$ activated that as peroxolike $O_2^{2-}$.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.851-855
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• 2002

Seven ergosterol derivatives (1-7) were isolated from silkworm larvae infected with Paecilomyces sp. J300. On the basis of spectroscopic means, their structures have been elucidated as 3$\beta$,5$\alpha$-dihydroxy-ergosta-7,22-diene (1), 5$\alpha$,6$\alpha$-epoxy-(22E,24R)-ergosta-8(14), 22-diene-3$\beta$,7$\alpha$-diol (2), 5$\alpha$,6$\alpha$-epoxy-(22E,24R)-ergosta-8, 22-diene-3$\beta$,7$\alpha$-diol (3), ergosta-4, 6, 8(14), 22-tetraene-3-one (4), ergosterol (5), ergosterol endoperoxide (6), 3$\beta$,5$\alpha$-dihydroxy-6$\beta$-methoxyergosta-7,22-diene (7). Compounds 3~7 showed moderate cytotoxicity against five tumor cells.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.837-841
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• 2002

Four new acetylated ginsenosides were isolated from the processed ginseng (SG, sun ginseng). Their structures were determined to be $3{\beta},{\;}12{\beta}-dihydroxydammar-20(22),24-diene-3-O-{\beta}-D-glucopyranosyl(1{\rightarrow}2)-{\beta}-D-6"-O-acetylglucopyranoside;{\;}3{\beta},12{\beta}-dihydroxydammar-20(21),{\;}24-diene-3-O-{\beta}-D-glucopyranosyl(1{\rightarrow}2)-{\beta}-D-6"-O-acetylglucopyranoside;{\;}3{\beta},{\;}6{\alpha},12{\beta}-trihydroxydammar-20(22),24-diene-6-O-{\beta}-D-6'-O-acetylglucopyranoside{\;}and{\;}3{\beta},6{\alpha},12{\beta}-trihydroxydammar-20(21),24-diene-6-O-{\beta}-D-6'-O-acetylglucopyranoside$ based on spectroscopic evidences. The compounds were named ginsenoside $Rs_4,{\;}Rs_5,{\;}RS_6{\;}and{\;}Rs_7$, respectively.pectively.

• Journal of the Korean Chemical Society
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• v.23 no.5
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• pp.286-295
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• 1979

In order to predict the effect of Lewis acid catalysis on the regioselectivity of the Diels-Alder reactions between unsymmetrically substituted dienes and dienophiles, the frontier orbital theory applied to the theoretical model of the Lewis acid complexed dienophile was studied by means of CNDO/2 MO. In the majority of reactions, CNDO/2 calculations gave good results in accordance with experimental orientation. Also, it was shown that the secondary orbital interaction played an important role in the regioselectivity of the Diels-Alder reaction between unsymmetrically substituted dienes and dienophiles. Although ANH's treatment is mathematically simpler than other methods, ANH's method which laid emphasis on dissymmetrical transition state gave good results on decision of regioselectivity.