• YAKHAK HOEJI
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• v.33 no.6
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• pp.361-364
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• 1989

The Synthesis of acyclic derivatives of ribavirin (2'-azido and halo seco derivatives) for the development of new antiviral agents is described. These acyclic nucleosides are synthesized from ribavirin by the method of ring opening reaction of sugar moietry.

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.1981-1984
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• 2006

Novel amphiphilic, thermo-responsive polyaspartamides which showed both LCST (lower critical solution temperature), and sol-gel transition were prepared and characterized. The polyaspartamide derivatives were synthesized from polysuccinimide, the polycondensate of aspartic acid monomer, via successive nucleophilic ring-opening reaction by using dodecylamine and N-isopropylethylenediamine (NIPEDA). At the intermediate composition ranges, the dilute aqueous solution exhibited a thermally responsive phase separation due to the presence of LCST. The phase transition temperature was controllable by changing the content of pendent groups. In addition, a physical gelation, i.e. the sol-gel transition was observed from the concentrated solutions, which was elucidated by dynamic viscoelastic measurements. These novel injectable and thermo-responsive hydrogels have potential for various biomedical applications such as tissue engineering and current drug delivery system.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.1 s.20
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• pp.69-80
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• 2005

A synthesis of azide-terminated glycidyl azide polymer, GAP-A, was carried out by tosylation and azidation of polyepichlorohydrin(PECH) prepared by cationic ring-opening polymerization. Polyepichlorohydrin was prepared by cationic activated monomer polymerization using ethylene glycol and $BF_3{\cdot}OEt_2$ as an initiator and a catalyst at $\~10^{\circ}C$. Tosylation of polyepichlorohydrin was performed using traditional TsCl/pyridine method and was also carried out using TsCl/amine catalysts to reduce the reaction time significantly. Azidation of tosyl-terminated PECH(OTs-PECH) was performed using $NaN_3$ as an azidation reagent in DMF solvent at high temperature and was unexpectedly completed within 2 hours.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.2 s.17
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• pp.109-117
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• 2004

We synthesized energetic prepolymer(2-nitrato ethyl oxirane, NEO) for plastic-bonded explosive and measured its thermodynamic parameters. 2-Nitrato ethyl oxirane(NEO) as a monomer was synthesized from 4-butene-ol, the first-step was preparation of 1-nitrate-3-butene and second-step was synthesized 2-nitrate-ethyl oxirane from 1nitrate-3-butene and then polymerized by cationic ring opening polymerization. The unreacted monomer concentration was measured by GC. The thermodynamic parameters were obtained from the ceiling temperature(Tc) values of 1 mole monomer at each reaction temperature. We varied feed rate of monomer, concentration of initiator and monomer to control molecular weight and polydispersity of perpolymer(NEO). Number average molecular weight(Mn), polydispersity(PD), and glass transition temperature(Tg), viscosity of prepolymer(NEO) were 2000, 1.07, $-55^{\circ}C$ and 300 poise respectively.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.840-844
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• 2010

The new MPV type reagent, Al-methanesulfonyldiisobutylalane ($DIBAO_3SCH_3$), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined in order to find out a new reducing system with high selectivity in organic synthesis. In general, the reagent is extremely mild, showing only reactivity toward aldehydes, ketones and epoxides. The reagent exhibits a unique reducing applicability in organic synthesis. Thus, the reagent can achieve a clean 1,2-reduction of $\alpha,\beta$-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in 100% purity. In addition, the reagent shows an excellent regioselectivity in the ring-opening reaction of epoxides. Finally, $DIBAO_3SCH_3$ shows a high stereoselectivity in the reduction of cyclic ketones to produce the thermodynamically more stable epimers exclusively.

• Bulletin of the Korean Chemical Society
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• v.19 no.6
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• pp.680-685
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• 1998

Two kinds of new aliphatic diols were synthesized by the ring-opening reaction of lactide and glycolide with 1,4-butanediol, a difunctional initiator, in the presence of stannous octoate. The resulting aliphatic diols were melt-polymerized with D-tartaric acid at 150 ℃ to produce new crosslinkable polyesters. They were reacted with hexamethylene diisocyanate in THF at 65 ℃ in a teflon mold for 24 h to prepare sequentially ordered crosslinked polyesters (BD/LT/GL/D-tartarate). Degradation of the prepared yellow crosslinked films was carried out in a buffer solution in order to examine the effect of time, pH, temperature and crosslinking degree on their degradation rate and mechanism. The rate of degradation increased with an increase in pH and temperature, but it decreased with increasing degree of crosslinkage incorporated into the crosslinked polyesters. We also found that the crosslinked polymers were converted into the acidic compounds such as lactic, glycolic, and D-tartaric acids during the degradation.

• Macromolecular Research
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• v.17 no.5
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• pp.346-351
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• 2009

$TiCl(O-i-Pr)_3/SiO_2$ and $Ti(O-i-Pr)_4/SiO_2$ were prepared by immobilizing chlorotitanium (IV) isopropoxide ($TiCl(O-i-Pr)_3$) and titanium (IV) isopropoxide ($Ti(O-i-Pr)_4$), to pretreated silica. The effect of the polymerization reaction conditions on the catalytic activity and characteristics of the resulting PLA were investigated. The catalytic conversion, molecular weight and polydispersity index (PDI) of the PLA produced on the titanium alkoxide supported catalysts increased proportionally with the reaction temperature. When the PLA was synthesized in bulk polymerization, the PLA produced with the supported catalysts had higher molecular weight than those with homogeneous catalysts. The melting temperature of the polymer produced with silica supported alkoxide catalysts was approximately $170-180^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.51-56
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• 2008

The regioselective ring opening of epoxides using elemental iodine and bromine in the presence of methimazole (MMI, a anti-thyroid drug) and its metabolite methimazole-disulfide as new catalysts are studied. MMI easily converted in vitro to MMI-disulfide without any double activation presented in vivo. FT-Raman and UV spectroscopies are used to study the interaction of iodine with these catalysts. The results indicate that both catalysts are efficient in polyiodide formation, but MMI-disulfide can catalyze this reaction in higher yield and regioselectivity. The complex [(MMI-disulfide)I]+.I3- is considered to be formed initially which could be bulkier by addition of excess of iodine in the course of the reaction. These bulky nucleophiles have a fundamental role in the high regioselectivity by attacking the less sterically hindered epoxide carbon. In this study we suggest that MMI is readily converted to MMI-disulfide by interaction with iodine or activated iodine in thyroid gland, and this process is responsible for high anti-thyroid activity of MMI.

• Journal of the Korean Chemical Society
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• v.53 no.3
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• pp.340-344
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• 2009

HEMA/vinyl-substituted polyphosphazene was prepared by the ring-opening polymerization of phosphonitrillic chroride trimer at $200{\sim}300\;{^{\circ}C}$, followed by Grignard reaction with vinyl magnesium bromide and then by the reaction with HEMA(2-hydroxyethyl methacrylate). HEMA/vinyl-substituted polyphosphazene was copolymerized with EGDMA(ethylene glycol dimethacrylate; used as a cross-linker for the free-radical copolymerization), NVP (N-vinyl-pyrrolidone) in the presence of AIBN (azobisisobutyronitrile) as a radical initiator. The oxygen transmissibility, water content and visible-ray transmissibility of the resulting copolymer were measured to be Dk/t 88, 30.89% and 87%, respectively, indicating that the copolymer can be used as a good contact lens material.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.132-137
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• 2015

BEA-zeolite was modified by alkaline solution to introduce mesoporosity in the crystals and the homogeneous chiral Co(III) salen was immobilized in the mesopores. The dinuclear chiral Co(salen)-$GaCl_3$ catalyst immobilized on mesoporous BEA-zeolite showed high activity for the regioselective ring opening of terminal epoxides by carboxylic acids. Various chiral monoester derivatives could be synthesized with moderate enantioselectivity (47~69 ee%) from racemic epoxides through above reaction. When the chiral (S)-ECH was used as a reactant, it was efficiently resolved by carboxylic acid with a high enantioselectivity in the presence of heterogenized chiral salen catalyst, and the ring opened product afforded optically pure monoester epoxide (R)-GB (up to 98 ee%) through the ring closing in the basic solution by elimination of HCl. The heterogeneous catalyst could be fabricated easily, and the catalytic activity was retained for several times reuse without any further regeneration step.