• Fibers and Polymers
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• 제5권2호
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• pp.83-88
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• 2004

In order to assess the potential of the hydroxy-containing polyamic acid (PHAA) synthesized from 3,3'-dihydroxy benzidine and pyromellitic dianhydride for a fire-safe polymer, the cyclization pathway of PHAA has been investigated using a model compound prepared from 2-aminophenol and phthalic anhydride. The reaction was monitored. by $^1{H-nuclear}$ magnetic resonance. N-(2-hydroxyphenyl) phthalamic acid is converted to N-(2-hydroxyphenyl) phthalimide at ca. 175$^{\circ}C$, showing endothermic reaction. The imide structure is rearranged to the benzoxazole structure over ca. $400^{\circ}C$. These results are similar with that of PHAA. According to pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) data, water and carbon dioxide are released during the cyclization and rearrangement reaction. One DMAc molecule is complexed with one carboxyl acid group in PHAA, which accelerates the imidization process to release more easily the flame retardant, water.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.186.4-187
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• 2003

Acanthoside-D, one of major components of Acanthopanacis Cortex, is known as a ginseng-like substance. it has been known to possess diverse biological effects. Acanthoside-D has a furofuran lignan structure and the synthesis of which poses interesting and often unsolved proplems of stereocontrol. Although a few interesting syntheses providing this natural product have been reported, an intermolecular McMurry coupling - intramolecular Mitsunobu cyclization route has not yet been explored. We report here a short and efficient synthetic pathway to the total synthesis of Acanthoside-D from aryl aldehydes and methyl acrylates via Baylis-Hillman reaction, intermolecular McMurry coupling and intramolecular Mitsunobu cyclization as key reaction.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2012년도 정기총회 및 춘계학술발표회
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• pp.20-20
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• 2012

Isoprenoids represent the most diverse group of metabolites, which are functionally and structurally identified in plant organism to date. Ginsenosides, glycosylated triterpenes, are considered to be the major pharmaceutically active ingredient of ginseng. Its backbones, categorized as protopanaxadiol (PPD), protopanaxatriol (PPT), and oleanane saponin, are synthesized via the isoprenoid pathway by cyclization of 2,3-oxidosqualene mediated with dammarenediol synthase or beta-amyrin synthase. The rate-limiting 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), which is the first committed step enzyme catalyzes the cytoplasmic mevalonate (MVA) pathway for isoprenoid biosynthesis. DXP reductoisomerese (DXR), yields 2-C-methyl-D-erythritol 4-phosphate (MEP), is partly involved in isoprenoid biosynthesis via plastid. Squalene synthase and squalene epoxidase are involved right before the cyclization step. The triterpene backbone then undergoes various modifications, such as oxidation, substitution, and glycosylation. Here we will discuss general biosynthesis pathway for the production of ginsenoside and its modification based on their subcellular biological functions.

• Bulletin of the Korean Chemical Society
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• 제15권2호
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• pp.154-161
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• 1994

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethylthioalkyl)phthalimides (alkyl=ethyl, n-propyl, n-butyl, n-pentyl, and n-hexyl). Photocyclizations occur in methanol in modest to high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from sulfur in the ${\alpha}$-silylmethylthioalkyl groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate ${\alpha}$ -silylmethylthio cation radicals and cyclization by radical coupling is proposed. In contrast, photoreactions of N-(trimethylsilylmethylthioalkyl)phthalimides in acetone follow different reaction routes to produce another cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon ${\alpha}$ to silicon and sulfur atoms via triplet carbonyl hydrogen abstraction pathway. The normal singlet SET pathway dominates this triplet process for photoreactions of these substances in methanol while the triplet process dominates the singlet SET pathway for those in acetone. The efficient and regioselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Bulletin of the Korean Chemical Society
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• 제24권3호
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• pp.357-362
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• 2003

The pathway producing imide ring closure during the thermal imidization of poly(amic acid) (PAA) was investigated in detail using a new analytical method, two-dimensional (2D) Raman correlation spectroscopy. The signs of the cross peaks in synchronous spectra provided evidence of the thermal imidization of PAA into PI as the heating temperature increased. The signs of the cross peaks in asynchronous spectra suggested that the imide-related modes changed prior to the amide or carboxylic mode, which indicates that cyclization occurred before the amide proton was abstracted.

• Bulletin of the Korean Chemical Society
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• 제13권2호
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• pp.166-172
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• 1992

Studies have been conducted to explore single electron transfer (SET) induced photocyclization reactions of N-(trimethylsilylmethoxyalkyl)phthalimides(alkyl=E thyl, n-propyl, n-butyl, n-pentyl, and n-octyl). Photocyclizations occur in methanol in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the trimethylsilyl group. Mechanism for these photocyclizations involving intramolecular SET from oxygen in the $\alpha-silylmethoxy$ groups to the singlet excited state phthalimide moieties followed by desilylation of the intermediate $\alpha-silylmethoxy$ cation radicals and cyclization by radical coupling are proposed. In contrast, photoreaction of N-(trimethylsilylmethoxyethyl) phthalimide in acetone follows different reaction routes to produce two cyclized products in which carbon-carbon bond formation takes place between the phthalimide carbonyl carbon and the carbon $\alpha$ to silicon and oxygen atoms via triplet carbonyl hydrogen abstraction triplet carbonyl silyl group abstraction pathways. The normal singlet SET pathway dominates these triplet processes for photoreaction of this substance in methanol. The efficient and regioselective cyclization reactions observed for photolysis in methanol represent synthetically useful processes for construction of medium and large ring heterocyclic compounds.

• Plant Resources
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• 제1권1호
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• pp.33-37
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• 1998

Carotenoid compounds in embryos of wild-type(WT) and viviparous mutants of maize(Zea mays L.) were analyzed using high performance liquid ehromatography (HPLC) with a photodiode array detector. Zeaxanthin accumulates in WT embryos as the major carotenoid. Phytoene accumulates in vp2 and vp5. Phytofluene in w3 and ${\xi}$-carotene in the vp9 mutant embryos. This indicates that the vp2 and vp5 mutants impair phytoene desaturase from 15-cis-phytoene to 15-cis-phytofluene. The w3 mutant has neither an isomerase from 15-cis-phytofluene to all-trans-phytofuene nor phytofluene desaturase from phytofluene to ${\xi}$-carotene. The vp9 mutant does not have the ${\xi}$-carotene desaturase from ${\xi}$-carotene to lycopene. Our analysis shows that the terminal carotenoid. ${\gamma}$-carotene(${\beta},{\Psi}$-carotene), accumulates in the vp7 mutant embryos. The ${\varepsilon}$-carotene(${\varepsilon},{\varepsilon}$-carotene), a product of ${\delta}$-carotene(${\varepsilon},{\Psi}$-carotene) in some plants, however, has not been found in maize embryos. The vp7 mutant impairs a cyclization step from ${\gamma}$-carotene to both ${\beta}$-carotene and ${\alpha}$-carotene. We suggest that monocyclic ${\gamma}$-carotene is the sole precursor of both bicyclic ${\beta}$-carotene(${\beta},{\beta}$-carotene) and ${\alpha}$-carotene(${\beta},{\varepsilon}$-carotene) in maize.

• 생약학회지
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• 제37권1호통권144호
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• pp.60-66
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• 2006

Norditerpene alkaloids are the main toxic principles of traditional oriental herb 'chuawu(bu-shi),' which have been used in Chinese materia medica mainly for the treatment of musculoskeletal disorders. They are biosynthesized via cyclization of geranylgeranyl pyrophosphate, incoration of 2-aminoethanol and decarboxylation not via amino acid pathway, and the structural characteristics have tempted several oxidative reactions. In this study various norditerpene alkaloids were subjected to react active manganese dioxide and oxoammonium salt as oxidants. The oxidation was proceeded as dealkylation with aconitine type and dehydrogenations with lycoctonin and heteratisine type.

• Journal of Ginseng Research
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• 제33권3호
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• pp.212-218
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• 2009

인삼으로부터 뽑은 PgCYP 유전자와 표지유전자인 NPTII 유전자를 함유하고 있는 Agrobacterium tumefaciens GV3101균주를 이용하여 담배 잎절편과 공동배양한 후 MS 기본배지에 kanamycin 100 $\mu$g/ml, cefotaxime 500 $\mu$g/l, BA 2 mg/l와 NAA 0.2 mg/l가 첨가된 선발배지에 치상하여 4주 후 항생제가 첨가된 기본배지에서 발근시켰다. 생존한 선발체의 잎을 이용하여 PCR 반응으로 도입유전자의 삽입여부를 확인하였다. 또한 선발된 형질전환체를 이용하여 RT-PCR을 실시하여 PgCYP 유전자가 담배식물에 안정적으로 도입되어 전사되고 있음을 확인하였다.

• Journal of Photoscience
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• 제7권4호
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• pp.143-148
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• 2000

Studies have been conducted to explore single electron transfer(SET) promoted photocyclization of ($\omega$-phthalimidoalkoxy)acetic acids(alkoxy=ethoxy, n-propoxy and n-butyloxy). Photocyclizations occur in methanol or acetone in high yields to produce cyclized products in which phthalimide carbonyl carbon is bonded to the carbon of side chain in place of the carboxylic group. These photocyclizations are thought to proceed through pathways involving intramolecular SET from oxygen in the $\alpha$-carboxymethoxy groups to the singlet excited state phthalimide moieties followed by decarboxylation of the intermediate $\alpha$-carboxymethoxy cation fadicals and cyclizations by radical coupling. The photocyclizations occur ca. three times faster in both methanol or acetone with one equivalent of sodium hydroxide added to the reactions and occur slower in acetone than in methanol. The efficient and regiselective cyclization reactions observed for photolyses in methanol represent synthetically useful processes for construction of heterocyclic compounds.