• Bulletin of the Korean Chemical Society
• /
• v.20 no.8
• /
• pp.917-920
• /
• 1999

The three stereoisomers of the 6,13-bis(thymidinyl)dioxocyclam 6 were synthesized through photoreaction of the chromium alkoxycarbene complex 2 and 1-(benzyloxycarbonyl)-4,4-dimethyl-D 2 -imidazoline. The molecular structure of (R,S)-6 was elucidated by X-ray crystallography.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.3
• /
• pp.325-328
• /
• 1999

In the reactions of the enolates of various 2-piperidineacetates with iodomethane or trisyl azide, the anti isomer was always predominant over the syn one, independent of the stereochemistry of the piperidineacetates. The piperidineacetates having OTBDMS moiety at C5 proceeded more diastereoselectively than the compounds without the substituent. The diastereoselectivity could be explained by perpendicular model for the electrophilic substitution reaction.

• Journal of the Korean Society of Industry Convergence
• /
• v.1 no.1
• /
• pp.43-49
• /
• 1998

The SS-phpm 4HCl(N,N'-bis-[2(S)-pyrrolidinylmethyl]phenylene-l,2-diamine-4-Hydrochloride) ligand having stereospecificity has been prepared and reacted with trans-[$Co(pyridine)_4Cl_2]$Cl. The resultants are purple crystals, which are identified to be ${\Delta}$-cis-${\beta}$-[$Co(SS-phpm)Cl_2$]Cl by elemental analysis and UV/Vis- and CD-absorption spectra, The conformation of SS-phpm in ${\Delta}$-cis-${\beta}$ complex is ${\delta}$ ${\varepsilon}$ ${\lambda}$ (SSSS) for each of the five-membered chelated ring. Futhermore, according to orientation of secondary amine, total strain energy on each isomers was calculated by molecular mechanics(MM) to verify structural characterization and spectral data. As the result, the most stabilized isomer was ${\Delta}$-cis-${\beta}$(SSSS). The value of total strain energy(U) of ${\Delta}$-cis-${\beta}$(SSSS) isomer was 63.21 kcal/mol, respectively.

• Journal of the Korean Chemical Society
• /
• v.29 no.4
• /
• pp.419-425
• /
• 1985

N-Methylamidinoglycine, an isomer of creatine which was postulated to be formed enzymatically in vitro, has been synthesized by coupling glycine with N, S-dimethylthiopseudouronium iodide in a yield of approxirnately 60%. On heating in acidic solution, it was converted to a cyclized form (isocreatinine) in analogy with the conversion of creatine to creatinine(anhydrous form). Structures were confirmed by an elemental analysis and proton NMR spectroscopy. Further studies on their characteristics were compared with those of creatine and creatinine in regard to isoelectric points(pI), retardation coefficients(Rf) on thin layer chromatography, and elution profiles on amino acid analyzer. In order to facilitate the comparison, $^{14}C$-labeled creatine, creatinine, isocreatine and isocreatinine were also synthesized.

• Journal of Environmental Health Sciences
• /
• v.40 no.1
• /
• pp.38-46
• /
• 2014

Objectives: This study was carried out in order to estimate atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations and sources using pine needles as a passive air sampler (PAS) in urban (Pyeongtaek), semirural (Anseong) and rural (Jincheon) sites. Methods: One-year-old pine needles were collected for analysis of their PAH concentrations ($C_{p,n}g/g$ dry) at the end of December. PAHs concentrations in the ambient air ($C_a$, $ng/m^3$) were calculated with a $Log(C_p/C_a)-LogK_{oa}$ correlational equation. Results: PAHs concentrations in ambient air ($C_a$) were high, in the order of urban ($114.03ng/m^3$), semirural ($105.17ng/m^3$) and rural ($61.91ng/m^3$) sites. However, distributions of PAH isomer concentrations were very similar. PAHs of which molecular weight is smaller than 228.30 (AcPy, Acp, Flu, Phen, Ant, Flt, Pyr, BaA, Chry) made up most of the PAHs in the ambient air (96.6-98.5%). Conclusion: At urban, semirural and rural sites, it was concluded that the main source of PAHs in the ambient air ratio of each PAH isomer concentration was cars, especially diesel vehicles.

• Journal of the Korean Institute of Gas
• /
• v.13 no.4
• /
• pp.40-45
• /
• 2009

In order to investigate the compatibility of data in MSDS(Material Safety Data Sheet), the flash point of xylene isomer was measured by using Pensky-Martens closed cup (ASTM D93), Setaflash closed cup(ASTM D3278), Tag open cup(ASTM D1310), and Cleveland open cup (ASTM D92) testers. Also, the AITs(autoignition temperatures) of xylene isomers were measured by using ASTM E659-78 tester. The measured the flash points and the AITs were compared with literatures and MSDS in KOSHA(Korea Occupational Safety and Health Agency). The measured the flash points and the AITs were different from those in literatures and MSDS. As a result, this paper is shown that it is needed to investigate combustion characteristics of xylene isomer for the fire safety objectives.

• Journal of Magnetics
• /
• v.17 no.2
• /
• pp.83-85
• /
• 2012

Magnetic particles in a novel, wound-healing ointment were studied using M$\ddot{o}$ssbauer spectroscopy and VSM to estimate the stability of the properties of the magnetic particles. The isomer shifts of $Fe_3O_4(A)$ were found to be 0.49-0.56 mm/s relative to iron metal, this indicates that the iron ions in $Fe_3O_4(A)$ are $Fe^{3+}$. On the other hand, the isomer shifts of $Fe_3O_4(B)$ were found to be 0.91-1.13 mm/s relative to iron metal, this shows that the ion state of $Fe_3O_4(B)$ is a mixed state of $Fe^{2+}$ and $Fe^{3+}$. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (${\sim}10\;{\AA}$), differs from the stoichiometric one. It was found that the area ratio of the M$\ddot{o}$ssbauer subspectra of $Fe_3O_4(A)$ / $Fe_3O_4(B)$ taken at 87 and 181 K linearly increased in comparison to the initial pure magnetic particles, but the rate of increase of the area ratio at 181 K was about two times that at 87 K. From the magnetic hyperfine field, despite their small size, the particles exhibit no superparamagnetism.

• BMB Reports
• /
• v.33 no.3
• /
• pp.268-275
• /
• 2000

In contrast to the pyrimidine (6-4)pyrimidone photoproduct [(6-4) adduct], its Dewar valence isomer (Dewar product) is low mutagenic and produces a broad range of mutations with a 42 % replicating error frequency. In order to determine the origin of the mutagenic property of the Dewar product, we used experimental NMR restraints and molecular dynamics to determine the solution structure of a Dewar·lesion DNA decamer duplex, which contains a mismatched base pair between the 3'-T residue and an opposed G residue. The 3'-T of the Dewar lesion forms stable hydrogen bonds with the opposite G residue. The helical bending and unwinding angles of the DW/GA duplex, however, are much higher than those of the DW/AA duplex. The stable hydrogen bonding of the G 15 residue does not increase the thermal stability of the overall helix. It also does not restore the distorted backbone conformation of the DNA helix that is caused by the forming of a Dewar lesion. These structural features implicate that no thermal stability, or conformational benefits of G over A opposite the 3'-T of the Dewar lesion, facilitate the preferential incorporation of an A. This is in accordance with the A rule during translesion replication and leads to the low frequent $3'-T{\rightarrow}C$ mutation at this site.

• Journal of the Korean Applied Science and Technology
• /
• v.16 no.3
• /
• pp.255-262
• /
• 1999

The new copolymers which contain flexible spacers in main chain were prepared and their properties were studied. the copolymers were synthesized in the melt polymerization melted from diacetoxynaphthalene isomers, ${\alpha},{\omega}bis(4-carboxyphenoxy)$ alkanes and p-acetoxy benzoic acid in the molar ratio of 1:1:2 and characterized for the effects of structure of naphthalenediol isomer moieties and the spacers on thermal crystalline and liquid crystalline properties of the resulting polymers. Diacetoxy naphthalene isomers were used 1. 5-,1. 6-,2. 6-and 2. 7-disubstituted ones and the spacers was either tetramethylene or decamethylene. The polymer was characterized by elemental and spectropic analysis, differential scanning calorimetry (DSC) on a polaring microscope, wide-angle X-ray diffractometry and thermogravimetry (TGA). There glass transition temperatures (Tg) and melting temperature (Tm) on the structure of the naphthalenediol isomer moieties and the length of the spacers. The presence of spacers was found to the helpful in crystallization of 1. 6-naphthalenediol copolyesters. The presence of amide group in the backbone chain of polymer was found to increase transition temperature, crystallization, thermal stability of polymers but to decreas solubility.

• Archives of Pharmacal Research
• /
• v.19 no.6
• /
• pp.535-542
• /
• 1996

Seven isoazamitosene derivatives, mitomycin analogues, were synthesized and tested for cytotoxicities against leukemia and gastric cancer cell lines. Preparation of a pyrrolo[1, 2-a]benzimidazole (3) (azamitosene ring system) was completed by utilizing the Lewis acid-catalized cyclization, with .omicron.-chloronitrotoluene as the starting material. Nitration of 3 produced a mixtue of two isomers (5-nitro isomer (4) and 7-nitro isomer (5)) in product ratio of 36 : 52. 4 was directly converted into quinone (7) by reduction and Fremy oxidaton. Finally, quinone derivatives (8, 9, 10, and 11) were synthesized by 1, 4-addition of 7 with cyclic secondary amines. From above-mentioned 5, 8-nitro compound (15) was prepared in 4 steps. At pH 3, Fremy oxidation of 15 produced quinone (16), whereas iminoquinone derivatives (17a and 17b) at pH 7. Isoazamitosene derivatives (8, 9, 10, and 11), containing cyclic amino groups at the 7-position, showed potent cytotoxicity on P388, SNU-1, and KHH tumor cell lines. Among them, 8 had stronger cytotoxicity against SNU-1 cell line than mitomycin and adriamycin. Considering these results, isoazamitosene derivatives may had unique cytotoxicity profiles. However, isoiminoazamitosene derivatives (17a and 17b) revealed very weak cytotoxicity.