• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.153-157
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• 2005

4-(Dimethylamino)pyridinium dichromate was synthesized by the reaction of 4-(dimethylamino)pyridine with chromium(VI)trioxide in $H_2O$, and characterized by IR, EA and ICP. The oxidation of benzyl alcohol using 4-(dimethylamino)pyridinium dichromate in various solvents showed that the reactivity increased with the increase of the dielectric constant, in the order: cyclohexen < chloroform < acetone < N,N-dimethylformamide. In the presence of hydrochloric acid(HCl), 4-(dimethylamino)pyridinium dichromate oxidized benzyl alcohol and its derivatives ($p-CH_3$, H, m-Br, $m-NO_2$) smoothly in N,N-dimethylformamide. Electron-donating substituents accelerated the reaction, whereas electron-withdrawing groups retarded the reaction. The Hammett reaction constant($\rho$) was -0.70 at 303K. The observed experimental data have been rationalized as follows: the proton transfer occurs after the prior formation of a chromate ester in the rate-determining step.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.375-376
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• 2000

• Bulletin of the Korean Chemical Society
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• v.20 no.11
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• pp.1373-1374
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• 1999

• Bulletin of the Korean Chemical Society
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• v.20 no.4
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• pp.400-402
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• 1999

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1301-1303
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• 1998

• Bulletin of the Korean Chemical Society
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• v.19 no.7
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• pp.730-732
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• 1998

• Archives of Pharmacal Research
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• v.9 no.4
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• pp.229-232
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• 1986

Three inexpensive oxidation reagents, namely pyridinium chlorochromate, chromium trioxide-dipyridine and nicotinium dichromate were utilized for oxidation of carbohydrates in 78-92% yield. Hydration could be eliminated in the oxidation of pentopyranosides and hexopyranosides, while pentofuranosides had a tendency to be easily hydrated during the oxidation. In the carbon-13 n. m. r. study, the carbonyl function resulted from the oxidation affected on the chemical shifts of $\alpha$- and $\beta$-carbons of methyl 3. 4-O-isopropylidene-$\beta$-D-arabinopyranosid-2-ulose (8) and 1,2 : 4, 5-di-O-isopropylidene-$\beta$-D-erythro-2, 3-hexodiulo-2, 6-pyranose (10) to slightly down fields (0.7-2.6 p. p. m.) compared with the chemical shifts before oxidation. While the carbonyl groups of 1. 2-O-isopropylidene-5-O-ethyloxycarbonyl-$\alpha$-D-erythro-pentofuran-3-ulose (4) and methyl 3, 5-0-isopropylidene-$\alpha$-D-threo-pentofuranosid-2-ulose (6) pushed the $\alpha$-carbons to up fields (3, 2-18.3 p. p. m. However, the order of signals on the spectra before and after oxidation remained unaltered.

• YAKHAK HOEJI
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• v.40 no.6
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• pp.621-624
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• 1996

Betaine was treated with hydrochloric acid and then with sodium borohydride to give a hydroxy compound 2. The reaction of 2 with thionyl chloride followed by thiourea led a comp ound 5. Oxidation of compound 2 with pyridinium dichromate(PDC) and succesive treatment with Lawesson's reagent also afforded the same compound 5. Cleavage of N-C14 bond compound of 7 was carried out via two reaction sequence from the compound 4. Finally, compound 10 was sythesized by a series of transformations from the compound 4.

• YAKHAK HOEJI
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• v.40 no.5
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• pp.487-490
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• 1996

The 13-hydroxyberbine(1), derived from berberinephenolbetaine, has been derivatized to furnish a variety of compounds such as 13-oxoberbine(2), 13-thioberbine(3), 13-chloroberbi ne(4), 13-(2-methylaziridine)berbine(5) and 13-carbolactoneberbine(6). Antitumor activity of these compounds was tested.