• Journal of the Korean Chemical Society
• /
• v.53 no.3
• /
• pp.377-381
• /
• 2009

• Korean Journal of Environmental Agriculture
• /
• v.10 no.2
• /
• pp.167-177
• /
• 1991

O-ethyl S-methyl ethylphosphonothioate [$LD_{50}$ (rat, oral) 4.6mg/kg ; $K_i$(bovine erythrocyte acetylcholinesterase) 303 $M^{-1\;min-1}$] was selected as a model compound to study the mode of action of O, S-dialkyl alkylphosphonothioates which have been hypothesized to be toxic via a bioactivation process. Two chemical oxidants, meta-chloroperoxybenzoic acid and monoperoxyphthalic acid, and rat liver microsomal oxidases were used to mimic the action of mixed function oxidases on the model compound. The formation of S-oxide, a very unstable active intermediate, was proposed based on the identification of metabolic products.Furthermore, a trapping experiment with ethanol showed that the unstable intermediate S-oxide had the ability to phosphorylate acetylcholinesterase which is an important enzyme in nerve systems. The S-oxide intermediates are presumed to be responsible for the toxicity of O,S-dialkyl alkylphosphonothioates.

• Elastomers and Composites
• /
• v.54 no.2
• /
• pp.105-109
• /
• 2019

Gold nanoparticles were synthesized by reacting potassium tetrachloroaurate ($KAuCl_4$), potassium carbonate ($K_2CO_3$), and isopropyl alcohol in the presence of fullerene oxide [$C_{60}(O)_n$, $n{\geq}1$], which was, in turn, prepared from [$C_{60}$] fullerene and m-chloroperoxybenzoic acid under refluxing conditions. The crystallinity and morphology of the prepared gold nanoparticles were confirmed by UV-vis spectroscopy, X-ray diffraction, and scanning electron microscopy. The activity of the gold nanoparticles in the reduction of 4-nitroaniline was measured in order to determine its capability as a catalyst.

• YAKHAK HOEJI
• /
• v.49 no.6
• /
• pp.443-448
• /
• 2005

Diosgenin (25 (R) - spirost-5-en-3$\beta$ -ol) was oxidized with 2,3-dichloro -5,6-dicyano-1,4-benzoquinone to form 25(R)-1,4,6-spirostatrien-3-one (1) as rigid cyclic $\alpha$,$\beta$-unsaturated carbonyl compound. This compound was reacted with $H_{2}O_{2}$, m-chloroperoxybenzoic acid (mCPBA), NaOCl in the presence with (R,R)- or (S,S)-Jacobsen catalyst, tert-butyl-hydroperoxide (TBHP) in Mo$(CO)_{6}$, and in VO $(acac)_{2}$ catalyst, respectively, 25(R) -1,4,6-spirostatrien -3-one (1) was reduced with $NaBH_{4}$ L-Selectride, $LiAIH_{4}$,$BH_{3}$ $\cdot$$(CH_{3})_{2}S$, Superhydride, Red-Al, and lithium tri-tert-butoxyaluminium hydride. And 25(R)-4,6-spirostadien-3$\beta$-ol (4) was treated with $H_{2}O_{2}$, mCPBA, TBHP in D - (-) - and L-(+)-diisopropyltar-trate and $Ti(OiPr)_{4}$ condition (Sharpless asymmetric epoxidation), TBHP in $Mo(CO)_{6}$, and in $VO(acac)_{2}$ catalyst, respectively.

• Elastomers and Composites
• /
• v.55 no.3
• /
• pp.199-204
• /
• 2020

Considering the immense applicability of isoprene rubbers, such as natural rubber (NR) and synthetic polyisoprene rubber (IR), attempts are being made to introduce more functionality within the rubber structure, e.g. epoxidation, to widen their technological viability. Epoxidation introduces polar epoxy bonds into the rubber molecular chain, resulting in enhanced intermolecular interactions among the rubber chains, increasing the oil resistance and air impermeability. Although there have been many reports on the epoxidation of NR in its latex form, there has been no such report using its solid form (or gum), which limits the epoxidation in terms of portability. Furthermore, the gum form has longer lifetime, while the latex form has limited lifetime for its efficient use. In this study, the epoxidation of natural rubber and polyisoprene rubber (using meta-chloroperoxybenzoic acid (mCPBA) as the epoxidizing agent) by dissolving their gum in hexane (i.e., the solution method) have been studied and compared. The effects of the amount of mCPBA, reaction time, and reaction temperature were investigated. The present process is easy and facilitates the epoxidation of rubbers in their solid form; therefore, it can be used for industrial upscaling of epoxidized rubber production.

• YAKHAK HOEJI
• /
• v.51 no.1
• /
• pp.56-62
• /
• 2007

Twelve epoxy and hydroxydiosgenin derivatives (DI-1${\sim}$DI-12) were synthesized from diosgenin (25(R)-5-spirosten-3${\beta}$-ol). Diosgenin was epoxidized with m-chloroperoxybenzoic acid (mCPBA) to oxidize 25(R)-4${\alpha}$,5${\alpha}$-epoxyspirostane (DI-1). Diosgenin was reacted with DDQ to form 25(R)-1,4,6-spirostatrien-3-one (DI-2), which was treated with 30% H$_2$O$_2$ to give 25(R)-1${\alpha}$,2${\alpha}$-epoxy-4,6-spirostadien-3-one (DI-3) and treated with mCPBA to form 25(R)-6${\alpha}$,7${\alpha}$-epoxy-1,4-spirostadien-3-one (DI-7), respectively. DI-3 was reduced with NaBH$_4$ to afford 25(R) -1${\alpha}$,2 ${\alpha}$-epoxy-4,6-spirostadien-3${\beta}$-ol(DI-4) and reacted with Li metal in absolute ethanol to form 25(R)-2-ethoxy-1,4,6-spirostatrien-3-one (DI-5). DI-7 was reduced with NaBH$_4$ to produce 25(R)-3${\beta}$,7${\alpha}$-dihydroxy-4-spirostene (DI-8) and treated with Li metal in liquid ammonia to produce 25(R)-7${\alpha}$-hydroxy-4-spirosten-3-one (DI-9). DI-2 was reduced with NaBH$_4$ to form 25(R) -4,6-spirestadien-3${\beta}$-ol(DI-10), which was stirred with 30% H$_2$O$_2$ to synthesize 25(R)-4,6-spirostadien-3-one (DI-11) and reacted with mCPBA to give 25(R)-4${\beta}$,5${\beta}$ -epoxy-6-spirosten-3${\beta}$-ol (DI-12), respectively. The antinociceptive effects of synthesiz ed compounds were measured by hot plate method and compound DI-7 signifcantly exhibited antinociceptive effect. DI-2 decreased the serum triglyceride and total cholesterol levels in poloxamer P-407 injected rat.

• The Korean Journal of Pesticide Science
• /
• v.2 no.2
• /
• pp.10-15
• /
• 1998

The bimolecular inhibition rate constants of carbofuran and N-dimethylphosphinothioyl carbofuran(PSC) to acetylcholinesterase(AChE) were $7.7{\times}10^{5}\;M^{-1}{\cdot}min^{-1}$ and $1.2{\times}10^{3}\;M^{-1}{\cdot}min^{-1}$, respectively. These results showed that PSC required a bioactivation process for its toxic action because it didn't inhibit the target enzyme effectively. The potency of PSC as an inhibitor of AChE increased when PSC and AChE were incubated with microsomes fortified with NADPH compared with microsome alone. Piperonyl butoxide(PBO) addition to these coupled systems greatly reduced the inhibition of the target enzyme by blocking the bioactivation process. In vivo inhibition study of mouse brain AChE, $I_{50}$ value for AChE was 28 mg/kg for PSC and the value increased to 57 mg/kg when PBO was pretreated. This result showed that cytochrome $P_{450}$ would also play a role in the bioactivation process of PSC in vivo. And conversioin of carbofuran from PSC was 55 % in a chemical oxidation system using meta-chloroperoxybenzoic acid. The oxidative activation of PSC to carbofuran was shown to be essential for showing its toxicological action and cytochrome $P_{450}$ was identified as an important enzyme which participated in this process.