• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.3017-3024
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• 2012

The geometrical parameters, vibrational frequencies, and binding energies for $(H_2O_3)_n$ (n = 1-5) have been investigated using various quantum mechanical techniques. The possible structures of the clusters (n = 2-5) are fully optimized and the binding energies are predicted using energy differences at each optimized geometry. The harmonic vibrational frequencies are also determined and zero-point vibrational energies (ZPVEs) are considered for the better prediction of the binding energy. The best estimation of the binding energy for the dimer is 8.65 kcal/mol. For n = 2 and 3, linear structures with all trans forms of the HOOOH monomers are predicted to be the lowest conformations in energy, while the cyclic structures with all cis-HOOOH monomers are preferable structures for n = 4 and 5.

• 대한화학회지
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• 제20권3호
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• pp.236-239
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• 1976

광독성 물질인 쿠마린과 푸로쿠마린의 광화학반응을 분광분석, 삼중상태 켄칭, 형광법을 써서 연구하였다. 크산토톡신과 티민 또는 DNA 수용액의 광화학반응에서 ${\beta}$-카로텐을 켄치로 썼으나 아무런 켄칭이 일어나지 않는 것으로 보아 이 반응은 수명이 긴 크산토톡신의 삼중상태보다 수명이 짧은 들뜬 단일상태에서 일어나는 것으로 생각된다.

• 분석과학
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• 제6권4호
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• pp.391-394
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• 1993

볶은 지유(Sanguisorbae radix)의 에테르 가용성 분획으로부터 aegiceradienol(28-noroleana-12, 17-dien-$3{\beta}$-ol)을 분리 동정하였다. 이 화합물은 원래의 생약에는 존재하지 않으며 열처리에 의해 생성된 변이물로서 열처리 시간이 증가할수록 그 함량이 증가하였다.

• Bulletin of the Korean Chemical Society
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• 제23권5호
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• pp.721-726
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• 2002

Two new C2-symmetric chiral $\alpha-$ and w-Diimines incorporating bulky ferrocenylethylamine and their copper(I)complexes have been synthesized and characterized by analytical and various spectroscopic techniques. The catalytic activities of these complexes have been tested in the asymmetric cyclopropanation of a series of olefins with some diazoacetates to achieve varying degree of dia- and enantio-selectivities depending on the nature of the ligand, the substrates, and the reagents. Some mechanistic implication has been made with regard to the interactions among all these chemical species.

• Natural Product Sciences
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• 제10권2호
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• pp.69-73
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• 2004

Continuation of a phytochemical study of Cichorium intybus L. (Astraceae) growing in Egypt, resulted in the isolation and identification of a new sesquiterpene lactone 3,4-dihydrolactucin, in addition to the eight known compounds; kaempferol, isoscutellarin, cichoriin, umbelliferone, lupeol, lupeol acetate, ${\beta}-sitosterol$, and ${\beta}-sitosterol-3-O-glucoside$. Chemical structures of the isolated compounds were assigned based on different physical, chemical, and spectroscopic techniques including IR, UV, MS, 1D- and 2D-NMR spectra. Furthermore, the antimicrobial, and spasmogenic activities of some fractions and isolates were also assessed.

• Natural Product Sciences
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• 제16권4호
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• pp.203-206
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• 2010

A pyridyl alkaloid, 3-pyridylcarbinol (1) and benzoic acid derivatives, 4-hydroxy benzoic acid (2), 4-hydroxyactophenone (3), vanilic acid (4), and benzoic acid (5) were isolated from the rhizomes of Anemarrhena asphodeloides on the basis of spectroscopic and physicochemical analyses including 1D- and 2D- NMR techniques as well as by comparison of their data with the published values. Compounds 1 - 5 were isolated for the first time from this plant source.

• Journal of Photoscience
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• 제10권1호
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• pp.165-173
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• 2003

m-Phenylene-linked biscarbenes, bisnitrenes and carbenonitrenes can be formed photochemically from appropriate nitrogenous precursors. Generation of such reactive intermediates under matrix-isolation conditions allows for their characterization by spectroscopic techniques such as ESR, UV /vis and IR. The latter method is also useful in characterizing secondary products derived from these reactive intermediates. Computational chemistry methods complement experimental IR data, aiding, thus, in identification of such compounds. In addition electronic structure calculations help in developing qualitative and semi-quantitative models, which can be useful in predicting ground-state multiplicities. The parent systems of m-phenylene-linked carbenes and nitrenes have high-spin ground states, but a switching to lower multiplicity can be achieved by chemical substitution. The ground state and various low-lying excited states of m-phenylenecarbenonitrenes can be reasonably approximated by simple valence-bond depictions. Finally, m-phenylenecarbenonitrenes are photoreactive in the inert matrix isomerizing to cyclopropene derivatives.

• Natural Product Sciences
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• 제11권4호
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• pp.240-247
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• 2005

Phytochemical investigation of the berries of Juniperus phoenicea led to the isolation of 4 compounds, namely; scutellarin, isoscutellarin, shikimic acid and the new palmitoyl lactone derivative 16-hydroxy palmitic-1,16-olide. This is the first report for the occurrence of these compounds in the species grown in Libya. The identification of the isolated compounds was based on the application of different spectroscopic techniques. In addition, the antihepatotoxic effect of the aqueous decoction of the berries was investigated.

• Natural Product Sciences
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• 제6권1호
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• pp.44-48
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• 2000

Tiliacora racemosa Colebr. belongs to the family Menispermaceae, the biggest storehouse of diphenylbisbenzylisoquinoline (DBBI) alkaloids. Exhaustive chemical processing of the root of T. racemosa by the application of modern separation techniques yielded a DBBI alkaloid which was identified as tiliacorine using sophisticated spectroscopic methods $(UV,\;IR,\;^1H-NMR,\;Mass)$. Tiliacorine possesses neuromuscular blocking activity. It produces a dose dependent hypotensive effect in rats and cats, and this effect is blocked by atropine.

• Natural Product Sciences
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• 제17권4호
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• pp.261-266
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• 2011

During the process of screening for antioxidative effects of natural plants in Korea, by measuring the superoxide quenching activity, methanol extract of the whole plant, Galium verum var. asiaticum (Rubiaceae), was found to show potent antioxidant activity. Subsequent activity-guided fractionation of methanol extract of Galium verum var. asiaticum led to the isolation of five phenolic compounds. Using spectroscopic techniques, the chemical structures were elucidated as: caffeic acid (1), narcissin (2), rutin (3), luteolin-7-O-${\alpha}$-L-rhamnopyranosyl (1 ${\rightarrow}$ 2)-${\beta}$-D-glucopyranoside (4), and luteolin-7-O-${\beta}$-D-glucopyranoside (5). These compounds were isolated for the first time from this plant. Among them, compound 1 showed the most significant riboflavin-originated superoxide and xanthine-originated superoxide quenching activities. Compounds 3 and 4 exhibited mild superoxide quenching effects compared with vitamine C.