• 제목/요약/키워드: Ring opening

검색결과 328건 처리시간 0.035초

생체분해성 고분자의 합성 및 물성에 관한 연구 -Poly (glycine-co-lactic acid) 와 Poly (glycine-co-glycolic acid)- (Synthesis and Physical Properties of Biodegradable Polymers -Poly (glycine-co-lactic acid) and Poly (glycine-co-glycolic acid)-)

  • 성용길;김정엽
    • 대한의용생체공학회:의공학회지
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    • 제9권1호
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    • pp.37-46
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    • 1988
  • Synthetic biodegradable polymers are of great interest for biomedical applications such as surgical sutures and drug delivery systems. The copolymers of ${alpha}-amino$ acids and ${alpha}-hydroxy$ matrices having the required permeability for drugs. Poly (glycine.co-lactic acid) and poly (glycine-co-glycolic acid) have been synthesized by ring-opening polymerization. Morpholine-2, 5-diane, lactide, and glycolid have been used as starting materials for polydepsipeptides. The synthesized monomers and copoylmers have been identified by NMR and FT-lR spectrophotometer. The thermal properties and glass transition temperatures ($T_g$) of the copolymers have been measured by differential scanning calorimetry. The $T_g$ values of poly (glycine-co-lactic acid) and poly (glycine co.glycolic acid) are increased with increasing mole fraction of morpholine-2, 5-dione in the copolymers.

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깊은 직선 홈 시일의 윤활 성능해석 (Lubrication Performance Analysis of Deep Straight Groove Seal)

  • 이안성;김준호
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2003년도 학술대회지
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    • pp.193-200
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    • 2003
  • In this study a general Galerkin FE formulation of the incompressible Reynolds equation is derived for lubrication analyses of noncontacting mechanical face seals. Then, the formulation is applied to analyze the flexibly mounted stator-type reactor coolant pump seals of local nuclear power plants, which have deep straight grooves or plane coning on their primary seal ring faces. Their various lubrication performances have been predicted. Results show that the analyzed deep straight groove seal should have a net coning of less than $0.6\;{\mu}m$ to satisfy the leakage limit. And for the same amount of equilibrium opening force the plane coning seal requires to have a 3 times higher dimensionless coning than the deep straight groove seal.

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$\varepsilon$-caprolactone-grafted dextran 공중합체의 합성과 전기 방사에 관한 연구 (Synthesis and electrospinning of $\varepsilon$-caprolactone-grafted dextran)

  • Lee, Byoung-min;Narayan Bhattarai;Lee, Douk-rae;Kim, Hak-yong;Park, Soo-Jin
    • 한국섬유공학회:학술대회논문집
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    • 한국섬유공학회 2003년도 가을 학술발표회 논문집
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    • pp.257-258
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    • 2003
  • Crafting process consists of the reversible protection of the hydroxyl groups of the polysaccharide backbone by silylation, followed by the ring-opening polymerization (ROP) of $\varepsilon$-caprolactone (CL) initiated by the free remaining hydroxyl groups of the partially silylated dextran in the presence of tin-based catalysts. The last step relies upon the removal of silylating groups under mild acidic conditions yielding the desired amphiphilic graft copolymers.

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재발성 서혜부 탈장으로 오인된 지방모세포종 (Inguinal Lipoblastoma Mimicking Recurrent Inguinal Hernia)

  • 남소현;임윤정;김연미
    • Advances in pediatric surgery
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    • 제20권2호
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    • pp.58-61
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    • 2014
  • Palpable inguinal mass in children should be differentiated from inguinal hernia, hydrocele, lymph node, and tumor. Though using ultrasonography, fatty tumor would be misdiagnosed as incarcerated inguinal hernia containing fatty component. We experienced the huge inguinal lipoblastoma in 5-year-old girl mimicking recurrent incarcerated hernia. Laparoscopic exploration revealed it was not incarcerated hernia but well demarcated bulging mass from abdominal wall. Mass was about $10{\times}4{\times}3cm$ and extended from internal inguinal ring to saphenous opening. It was near total excised because of right external iliac vein injury. Pathologically, it was proven as lipoblastoma containing mature adipocyte with lipoblast and fibrous septa. Postoperatively, we noticed a segmental thrombotic occlusion of external iliac vein. After 1 year, she has no symptom related to occluded vessel. The remained lipoblastoma showed no interval change. Even lipoblastoma has a good prognosis with low recurrence rate, we need careful follow-up.

1,5-Diphenylhydantoins의 가수분해에 의한 N-Aryl Phenylglycine Ο-Alkyl Esters의 합성 (Synthesis of N-Aryl Phenylglycine Ο-Alkyl Esters Using Hydrolysis of 1,5-Diphenylhydantoins)

  • 박해선;최희전;권순경;박명숙
    • 약학회지
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    • 제47권3호
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    • pp.130-134
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    • 2003
  • For the development of new synthetic method for unnatural amino acid esters, N-aryl phenylglycine Ο-alkyl esters 4a∼i were synthesized through base-catalyzed hydrolysis of 1,5-diphenylhydantoins 1a∼b and Ο-alkylation in 16∼87% yield. An efficient and practical route for final 4a∼i was that the starting materials 1a∼b were heated in dil-methanol for 30 minute using sodium hydroxide or potassium hydroxide and evaporated. In addition, reaction mixture were refluxed for 1 h in DMF. All synthetic process from hydantoin to N-aryl phenylglycine Ο-alkyl esters 4a∼i could be carried out in one-pot without isolation of intermediates.

Acyclonucleoside 류의 합성(3) -Ribavirin 유도체의 합성- (Synthesis of Acyclonucleosides (3) -Synthesis of Ribavirin Derivatives-)

  • 문형룡;양재욱;김문환;천문우;정원근
    • 약학회지
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    • 제33권6호
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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.

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Synthesis of 4-Phenyltetralone Derivatives and Reaction Mechanism

  • Kwon, Soon-Kyoung;Park, Young-Nam
    • Archives of Pharmacal Research
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    • 제23권4호
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    • pp.329-331
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    • 2000
  • 4-(p-Chlorophenyl)tetralone (6) and 7-chloro-5-(p-chlorophenyl)tetralone (9) are key intermediates for the development of benzazepinone derivative haftens. These compounds could be synthesized from 4-phenyltetralone derivatives by triflic acid catalyzed Friedel-Crafts reaction. The reaction mechanism of Friedel-Crafts alkylation/acylation with lactones in triflic acid is presented. According to our tentative research, ring opening of protonated lactone (2) occurs in alkyl cleavage and the rate of the reaction is not dependent on concentration of triflic acid. So, alkylation of lactone in Friedel-Crafts reaction is presumed to be $A_{AL}$ 1. In second step, intramolecular acylation of the intermediates 4 to 6, 4 can be transformed to a triflic acid-carboxylic anhydride and then the cyclization is undergone after leaving of the triflate anion.

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피롤리딘의 개환과 N-프로텍티드 아미노 케톤의 형성; 5-아미노-2-펜타논 유도체의 합성 (Ring Opening of Pyrolidine and Formation of N-Protected Amino Ketones; Synthesis of 5-Amino-2-pentanone Derivatives)

  • 박명숙
    • 약학회지
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    • 제40권3호
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    • pp.300-305
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    • 1996
  • The base-induced elimination of N-protected 2-(bromomethyl)pyrrolidines 12a-c with KHMDS in THF at -78$^{\circ}C$ for 1h gave exocyclic enamines 13a-c. The acidic catalyzed pr otonation on ${\beta}$-carbon atom of 2-(methylene)pyrrolidines 13a-c with $H_3PO_4$ formed endocyclic N-iminium intermediates 14(or 15). Nucleophilic attack of alpha-carbon atom and hydrolysis of N-iminium ion gave carbocationic adduct (aminoalcohol) 16 from which 5-amino-2-pentanones 17a-c were formed after deprotonation.

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유기 티오엔아민 포스포네이트와 산화스티렌과의 반응 (The Reaction between Organothioenamine Phosphonate and Styrene Oxide)

  • 김근재;한치선
    • 대한화학회지
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    • 제20권4호
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    • pp.295-298
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    • 1976
  • Organothioenamine phosphonate와 styrene oxide 와의 반응에서 얻어진 생성물의 구조를 규명한 결과 그것이 cyclopropane 유도체임을 알았다. 이것은 반응이 styrene oxide에 대한 thioenamine phosphonate의 친핵공격에 의해서 생긴 산소 음이온이 다시 인 원자를 공격함으로서 중간체로 betain이 형성 된다음 이어서 약한 P-C 결합이 끊어지면서 생성물로 이끌어져 감을 가리켜 주고있다. 또한 생성물의 광학활성을 조사한 결과는 우회전성 이어서 이 반응은 중간체에서 생긴 benzyl carbon의 입체적 효과를 받으며 어디까지나 안정한 경로를 거쳐서 이끌어져 감을 알 수 있었다.

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Preparation of Biodegradable Thermo-responsive Polyaspartamides with N-Isopropylamine Pendent Groups (I)

  • Moon, Jong-Rok;Kim, Ji-Heung
    • Bulletin of the Korean Chemical Society
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    • 제27권12호
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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.