• Bulletin of the Korean Chemical Society
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• v.13 no.6
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• pp.588-592
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• 1992

A series of new ferrocene derivatives containing cyclohexylphosphines have been prepared from the reactions of lithioferrocenes with corresponding chlorodicyclohexylphosphines. 1-diphenylphosphino-1'-dicyclohexylphosphinoferro cene has been prepared from [1]-ferrocenophane via a ring cleavage reaction. Chiral ferrocenylaminophosphines incorporating cyclohexyl-and cyclopentadienylphosphines have also been prepared from the chiral template 2-N,N-dimethylaminoethylferrocene (FA) via stereoselective lithiation followed by phosphination with corresponding $R_2PCl$(R= $C_6H_{11}$, $C_5H_5$). The synthesis of cyclopentadienylphosphine derivative of (R)-FA (6b) led to the formation of a mixture of four diastereomers due to the presence of three chiral sources in the final product in addition to the fluxional behavior of the $η^1$-$C_5H_5$ group attached to the phosphorus. All these new compounds have been characterized by analytical and spectroscopic techniques.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.7-16
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• 1987

A study was undertaken to investigate the absorption, translocation and metabolism of carbofuran in rice paddies. Ring-3-$^{14}C-carbofuran$ applied onto the paddy soil surface was rapidly absorbed and translocated into rice plants. Within 2 days after treatment, it was observed that carbofuran reached shoot tips and accumulated. More than 15% of total radioactivity was recovered in rice plant from 3 to 20 days after treatment. In organic soluble fraction of rice plant extract, 3-hydroxycarbofuran was the major metabolite recording 43% and 4% of total organic soluble radioactivity in shoot and root at 20 days respectively. 3-Ketocarbofuran and phenolic metabolites including carbofuran phenol, 3-hydroxycarbofuran phenol and 3-ketocarbofuran phenol were also detected in the organic soluble fractions. Some glycosidic conjugates of carbofuran metabolites were found in water soluble fraction of rice plant extract and 3-hydroxycarbofuran was the most abundant aglycone. Radioactivity in paddy soil was rapidly decreased until 3 days after treatment and then maintained almost constant level. A significant portion (42∼56 %) of the total radioactivity remained in soil as nonextractable residue from 5 to 20 days after treatment. The nonextractable radioactivity was mainly located in soil organic matter distributing in humin, fulvic acid and humic acid fractions with the decreasing order. Evolution of $^{14}CO_2$ from ring cleavage of $3-^{14}C-carbofuran$ was negligible recording only 1.8% of total radioactivity during 20 days after treatment.

• Journal of the Korean Society of Food Science and Nutrition
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• v.3 no.1
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• pp.69-76
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• 1974

The method of amino acid sequence determination from the C-terminal amino acid is proposed and mass spectrometric identification of thiohydantoins described previously. In this paper was discussed the fragmentation of thiohydantoin-ring by deutero substitution and model tripeptide have been degraded through three stages each, with interpretable results. The conditions employed in this method are mild enough for biological materials. The main features of the method are the following. 1. Thiohydantoins were formed in a non-aqueous medium a mixture of acetic anhydride, acetic acid and ammonium thiocyanate. 2. Mass sepectra of thiohydantoins derived from 20 amino acids were obtained with a mass spectrometer, JEOL model JMS-06H. 3. Cleavage of peptidyl thiohydantoin was made with an acidic from of a cation-exchange resin. (Amberlite IR-120) 4. Separation of the cleaved thiohydantoin and the parent peptide less one amino acid moiety was made by chromatography on a Sephadex G-10 column. 5. The peptide fraction was concentrated by freezedrying. 6. Thiohydantoin derivative of carboxyl terminal amino acid residue was introduced with a direct inlet probe in methanol solution.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1253-1257
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• 2011

The surface structures, adsorption conditions, and thermal desorption behaviors of cyclopentanethiol (CPT) self-assembled monolayers (SAMs) on Au(111) were investigated by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). STM imaging revealed that although the adsorption of CPT on Au(111) at room temperature generates disordered SAMs, CPT molecules at $50^{\circ}C$ formed well-ordered SAMs with a $(2{\surd}3{\times}{\surd}5)R41^{\circ}$ packing structure. XPS measurements showed that CPT SAMs at room temperature were formed via chemical reactions between the sulfur atoms and gold surfaces. TDS measurements showed two dominant TD peaks for the decomposed fragments ($C_5H_9^+$, m/e = 69) generated via C-S bond cleavage and the parent molecular species ($C_5H_9SH^+$, m/e = 102) derived from a recombination of the chemisorbed thiolates and hydrogen atoms near 440 K. Interestingly, dimerization of sulfur atoms in n-alkanethiol SAMs usually occurs during thermal desorption and the same reaction did not happen for CPT SAMs, which may be due to the steric hindrance of cyclic rings of the CPT molecules. In this study, we demonstrated that the alicyclic ring of organic thiols strongly affected the surface structure and thermal desorption behavior of SAMs, thus providing a good method for controlling chemical and physical properties of organic thiol SAMs.

• Membrane Journal
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• v.13 no.2
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• pp.110-117
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• 2003

Sulfonated polyimides had been utilized and studied widely as available materials in chloro-alkali electrolysis, cationic exchange resins, and so on. However, a slow decrease in performance during experiments had been reported, which could be attributed to a loss of ionic conductivity related to either a continuous dehydration or polymer degradation. One of main reasons to account for the degradation of sulfonated polymers is the hydrolysis leading to polymer chain scission and decrement of molecular weight. Therefore, the objective of our study was to investigate possible imide cycle and additional ester bond cleavage connected with $SO_3$H presence under hydrated condition. In order to confirm and obtain as clear information as possible about breakages of bonds via $^1H\; and \;^{13}C$ NMR and IR spectroscopic analyses, our study was performed by model compound. Consequently, model compounds with both phthalic and naphthalenic imide ring and ester bonds were synthesized to evaluate the hydrolysis stability of sulfonated polyimide. The experiments were performed for prepared model compounds before and after aging in deionized water at $80^{\circ}C$ and were terminated by lyophilization technique. The aging products were finally analyzed by NMR and IR spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2213-2218
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• 2012

Efficient synthetic routes were developed to prepare a sizable amount (4-15 grams) of the chiral epoxides 4-6 as versatile intermediates for the synthesis of aspartyl protease inhibitors of therapeutic interest such as HIV protease and ${\beta}$-secretase. Oxidative cleavage of the C(2)-C(3) double bond of L-ascorbic acid followed by functional group manipulation led to the preparation of the epoxide 10, which was opened with an azide to yield a common aziridine intermediate 12. Through opening of the aziridine ring of 12 with either a carbon or a sulfur nucleophile, chiral epoxide precursors 4-6 could be prepared for various HIV protease inhibitors. Except for the final low melting epoxides 5 and 6, all intermediates were obtained as crystalline solids, thus the synthetic pathway can be easily applied to a large-scale synthesis of the chiral epoxides.

• Korean Journal of Environmental Agriculture
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• v.17 no.1
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• pp.5-10
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• 1998

The microbial degradation, photosensitizer-mediated photolysis, and bioceramic- accelerated degradation of the herbicide imazapyr were investigated using four types of soil. 1. Seven strains of microorganisms isolated from the soil A and the active sludge collected from the waste water disposal plant in CheongJu did not give any distinct degradation products in pure culture. When imazapyr (10ppm) was incubated for 14days with each of the 6strains of the known bacteria, they did not produce any noticeable products, either, suggesting that imazapyr was degraded very little by microorganisms in aqueous media. Meanwhile, when 50ppm of imazapyr was incubated in soil A and B for 6months, a degradation product of m/z 279 was detected. It turned out to be 2-[(1-carbamoyl-1,2-dimethylpropyl)carbamoyl]nicotinic acid, which was formed by the hydrolytic cleavage of the imidazolinone ring and by tautomerism. When imazapyr was exposed to sunlight, degradation rates were 14.6% under the control and 66.0, 76.5, 26.7, and 90.0% in the presence of PS-1 (100ppm), PS-1 (200ppm), PS-2(100ppm), and PS-3(100ppm), respectively, and a degradation product of m/z 149 was tentatively identified in the treatment of PS-1. 2. When soil C and D treated with bioceramic were incubated for 7weeks, the $^{14}C$-activities of $^{14}CO_2$ evolved were 2.03 and 1.12% of the originally applied ones, respectively, whereas those in control soils without bioceramic were 1.88 and 0.82% showing no significant defferences.After 5 weeks, however,the differences in the amounts of $^{14}CO_2$ between the two treatments increased gradually, suggesting the bioceramic effect.