• Title/Summary/Keyword: Conjugate addition

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A study on the improvement of the local stress field using the theory of conjugate approximations and loubignac's iterative method (공액근사개념과 Loubignac의 반복계산법을 이용한 국부응력장 개선에 대한 연구)

  • Song, Kee-Nam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.10
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    • pp.1598-1608
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    • 1997

  • Based on the application of te theory of conjugate approximations and the Loubignac's iterative method in a local region, a method to improve the stress filed in a displacement-formulated finite element solution has been proposed. The validity of the proposed method has been tested through two examples : a thick cylinder under internal pressure loading and an infinite plate with a central circular hole subjected to uniaxial tension. As a result of analysis of the examples, it was found that the stress field obtained for the local region model by the proposed method approximates well for the whole domain model. In addition, it was found that because of a significant decrease in the computing time to obtain the improved stress field, the proposed method is efficient and useful for the detailed stress analysis in local regions.

  • https://doi.org/10.22634/KSME-A.1997.21.10.1598 인용 PDF

Facile Synthetic Route to Ascorbic Acid-Dipeptide Conjugate via N-Terminal Activation of Peptide on Resin Support

  • Yang, Jin-Kyoung;Kwak, Seon-Yeong;Jeon, Su-Ji;Kim, Hye-In;Kim, Jong-Ho;Lee, Yoon-Sik
    • Bulletin of the Korean Chemical Society
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    • v.35 no.8
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    • pp.2381-2384
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    • 2014

  • A solid-phase synthetic approach is reported for the synthesis of an ascorbic acid (ASA)-dipeptide conjugate that exhibited enhanced antioxidant activity. The N-terminal amino group of dipeptide (Ala-Ala) on a resin support was first activated by 1,1'-carbonyldiimidazole (CDI), and then reacted with an ASA derivative. The addition of a base, triethylamine (TEA), promoted nucleophilic acylation of ASA derivative and yielded a desired product (ASA-Ala-Ala) with enhanced purity, when cleaved from the resin. Compared to the approach where a C3 hydroxyl group of ASA was first activated with CDI and then reacted with the amino group of dipeptide on the resin, this new approach allowed a significant reduction of a total reaction time from 120 h to 8 h at $25^{\circ}C$. As-prepared ASA-dipeptide conjugate (ASA-Ala-Ala) showed improved antioxidant activity compared to ASA.

  • https://doi.org/10.5012/bkcs.2014.35.8.2381 인용 PDF KSCI KPUBS HTML

The Stereospecific Synthesis of Abscisic Acid

  • Park, Oee-Sook;Lee, W.Y.;Park, J.C.
    • Korean Journal of Pharmacognosy
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    • v.17 no.1
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    • pp.67-72
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    • 1986

  • A stereospecific synthesis of 3-methyl-5-(1-hydroxy-4-oxo-2,6,6-trimethyl-2-cyclohexen-1-yl)-cis, trans-2,4-pentadienoic acid (abscisic acid) from ${\alpha}-ionone$ has been investigated. Ethyl 5-(2,6,6-trimetyl-2-cyclohexen-1-yl)-trans-4-penten-2-ynoate $({\alpha},{\beta}-acetylenic\;ester)$, which was synthesized from alpha-ionone in two steps, was stereospecifically converted in good yield into ethyl 3-methyl-5-(2,6,6-trimethyl-2-cyclohexen-1-yl)-cis, trans-2, 4-pentadienoate $({\alpha}-ionylideneacetate)$ by the conjugate addition of lithium dimethylcuprate at $-78^{\circ}C$. Basic hydrolysis of the ethyl ${\alpha}-ionylideneacetate$ gave an abscisic acid precursor, 3-methyl-5-(2,6,6-trimethyl-2-cyclohexen-1-yl)-cis, trans-2,4-pentadienoic acid, which can be oxidized to yield abscisic acid.

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