• 제목/요약/키워드: intramolecular cyclization

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Approach to the Total Synthesis of Acanthoside-D

  • Ngoc, Thyen-Truong;Park, Hae-Il
    • 대한약학회:학술대회논문집
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    • 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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    • pp.186.4-187
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    • 2003
  • Acanthoside-D, one of major components of Acanthopanacis Cortex, is known as a ginseng-like substance. it has been known to possess diverse biological effects. Acanthoside-D has a furofuran lignan structure and the synthesis of which poses interesting and often unsolved proplems of stereocontrol. Although a few interesting syntheses providing this natural product have been reported, an intermolecular McMurry coupling - intramolecular Mitsunobu cyclization route has not yet been explored. We report here a short and efficient synthetic pathway to the total synthesis of Acanthoside-D from aryl aldehydes and methyl acrylates via Baylis-Hillman reaction, intermolecular McMurry coupling and intramolecular Mitsunobu cyclization as key reaction.

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카본전극을 이용한 9-Methyl-2,3,6,7-tetramethoxyfluorene의 합성 (Electrolytic Synthesis of 9-Methyl-2,3,6,7-tetramethoxyfluorene with Carbon Electrodes)

  • 김덕현
    • 공업화학
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    • 제8권1호
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    • pp.39-48
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    • 1997
  • 카본전극을 이용한 양극산화을 통해 1,1-Bis-(3,4-dimethoxyphenyl)ethane으로부터 $CH_3CN$이나 $CH_2Cl_2/TFA$-혼합용액계에서 Intramolecular cyclizatlon 반응이 일어났다. Intramolecular cyclization에 의한 생성물(9-methyl-2,3,6,7-tetramethoxyfluorene)은 출발물질보다 더 쉽게 산화되고, 그에 따른 산화생성물은 $CH_3CN$계에서 불안정하여 낮을 수율을 나타냈다. TFA가 존재하는 계에서는 Fluorene 유도체의 산화생성물인 radical cation이 안정하여 환원 후에 더 좋은 수율로 합성할 수 있었다.

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Synthetic Studies on Jasmonoids(I): Jasmone, Dihydrojasmone, and Tetrahydrojasmone

  • Lee, Woo-Young;Lee, Yang-Suk;Jang, Se-Young;Lee, Sang-Yong
    • Bulletin of the Korean Chemical Society
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    • 제12권1호
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    • pp.26-31
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    • 1991
  • Facile and efficient syntheses of terpenic perfumeries cis-jasmone, dihydrojasmone, and tetrahydrojasmone have been investigated. Cis-jasmone was synthesized by successive metallation followed by alkylation of acetone N,N-dimethylhydrazone with (Z)-2-penten-1-yl tosylate (or 2-pentyn-1-yl tosylate) and propylene oxide in one flask to give a ketonic alcohol, which was oxidized to the corresponding diketone, followed by base-catalyzed intramolecular aldol condensation to give a regioselective cyclization product. Dihydrojasmone and tetrahydrojasmone could be conveniently obtained from 2-octanone. The dimethylhydrazone of the ketone was lithiated with butyllithium and reacted with propylene oxide to give a ketonic alcohol, which was oxidized to a diketone, followed by base-catalyzed intramolecular cyclization to afford dihydrojasmone. Tetrahydrojasmone was prepared by converting the ketonic alcohol into corresponding iodoketone, followed by base-catalyzed intramolecular cycloalkylation to furnish an odoriferous product.

Stereocontrolled Preparation of 2,6-Disubstituted 4-Methylenetetrahydropyrans by Lewis Acid Promoted Allylsilane-Acetal Cyclization

  • 성태명;곽우영;강경태
    • Bulletin of the Korean Chemical Society
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    • 제19권8호
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    • pp.862-868
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    • 1998
  • The Lewis acid mediated intramolecular additions of allylsilanes to acetal substrates are described. Excellent regio- and diastereoselectivity are achieved by boron trifluoride promoted cyclization of allysilane-acetals 5 and 8 derived from hydroxy allysilances 3. Cyclizations occur in moderate to high yields, providing directr routes to cis-2, 6-disubstituted 4-methylenetetrahydropyrans 6 and 9.

Synthesis of 3,4,5-Trisubstituted Isoxazoles through Gold-Catalyzed Cascade Cyclization-Oxidative Alkynylation and Cyclization-Fluorination of 2-Alkynone O-Methyloximes

  • Song, Doo-Hee;Ryu, Jae-Sang
    • Bulletin of the Korean Chemical Society
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    • 제35권9호
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    • pp.2635-2644
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    • 2014
  • Gold-catalyzed tandem cyclization-oxidative alkynylation and cyclization-fluorination reactions of 2-alkynone O-methyloximes are described. The reactions proceed smoothly at room temperature in the presence of 10 mol % of $(PPh_3)AuNTf_2$, 2.5 equivalents of selectfluor, and 2 equivalents of $K_3PO_4$. 2-Alkynone O-methyloximes undergo intramolecular oxyauration/cyclization and ensuing oxidative cross-coupling and fluorination process to afford the corresponding 3,4,5-trisubstituted isoxazoles in a cascade manner.

An Efficient Synthesis of Substituted Furans by Cupric Halide-Mediated Intramolecular Halocyclization of 2-(1-Alkynyl)-2-alken-1-ones

  • Fu, Wei-Jun;Xu, Feng-Juan;Guo, Wen-Bo;Zhu, Mei;Xu, Chen
    • Bulletin of the Korean Chemical Society
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    • 제34권3호
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    • pp.887-891
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    • 2013
  • An efficient synthesis of 3-halofurans by the intramolecular cyclization of 2-(1-alkynyl)-2-alken-1-ones with cupric halide has been developed. A broad range of 3-chloro- and 3-bromofuran derivatives could be obtained in the present method in moderate to good yields. The 3-halofuran derivatives are potential synthetic intermediates for amplification of molecular complexity.