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Volumn 129, Issue 5, 2007, Pages 1132-1140

Ambient temperature synthesis of high enantiopurity N-protected peptidyl ketones by peptidyl thiol ester-boronic acid cross-coupling

Author keywords

[No Author keywords available]

Indexed keywords

AMINO ACIDS; ESTERS; HIGH TEMPERATURE EFFECTS; STOICHIOMETRY; SYNTHESIS (CHEMICAL);

EID: 33846850351     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja0658719     Document Type: Article
Times cited : (123)

References (57)
  • 13
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    • (1994) Angew. Chem , vol.106 , pp. 1780-1802
    • Gante, J.1
  • 22
    • 33845558188 scopus 로고    scopus 로고
    • Buckley, T. F., III: Rapoport, H. J. Am. Chem. Soc. 1981, 103, 6157-6163.
    • Buckley, T. F., III: Rapoport, H. J. Am. Chem. Soc. 1981, 103, 6157-6163.
  • 30
    • 33846792442 scopus 로고    scopus 로고
    • Structure, Properties, and Preparation of Boronic Acid Derivatives: Overview of Their Reactions and Applications
    • Hall, D. G, Ed, Wiley-VCH Verlag GmbH & Co KGaA: Weinheim, Germany
    • Hall, D. G. Structure, Properties, and Preparation of Boronic Acid Derivatives: Overview of Their Reactions and Applications. In Boronic Acids; Hall, D. G., Ed.; Wiley-VCH Verlag GmbH & Co KGaA: Weinheim, Germany, 2005.
    • (2005) Boronic Acids
    • Hall, D.G.1
  • 43
    • 33846812975 scopus 로고    scopus 로고
    • Reactions carried out at high pressures of CO might well be successful, but were not pursued in favor of perturbing the reaction outcome through other variables as described in the text
    • Reactions carried out at high pressures of CO might well be successful, but were not pursued in favor of perturbing the reaction outcome through other variables as described in the text.
  • 44
    • 33846791850 scopus 로고    scopus 로고
    • Four-coordinate, square-planar palladium(II) complexes are coordinatively unsaturated (16-electron), but often react by further ligand loss to a three-coordinate, 14-electron intermediate.
    • Four-coordinate, square-planar palladium(II) complexes are coordinatively unsaturated (16-electron), but often react by further ligand loss to a three-coordinate, 14-electron intermediate.
  • 45
    • 33846843457 scopus 로고    scopus 로고
    • Extending the reaction time from 16 to 36 h or raising the reaction temperature from 50 to 60°C did not increase the yield of the ketone. However, an effective reaction was resumed when additional CuTC and phenylboronic acid were added to the reaction mixture after 14 h, an indication that the Pd catalyst was still robust. For example, a mixture of thiol ester N,N-bis-Boc-phenylalanine p, chlorophenylthiol ester (56.4 mg, 0.11 mmol, 1.0 equiv, CuTC (32.7 mg, 0.17 mmol, 1.5 equiv, phenylboronic acid (21.4 mg, 0.18 mmol, 1.5 equiv, Pd2(dba)3 (5.6 mg, 0.061 mmol, 0.05 equiv, PPh3 (11.9 mg, 0.045 mmol, 0.4 equiv, and PMe2Ph (6.5 μL, 0.045 mmol, 0.4 equiv) in 3 mL of dry THF was stirred at 50°C for 14 h. Then, additional CuTC (21.9 mg, 0.11 mmol, 1.0 equiv, phenylboronic acid 14.1 mg, 0.11 mmol, 1.0 equiv, and 1.0 mL of dry THF were added. The reaction was stirred for another 8 h at 50°C. After the aqueous wor
    • 2Ph (6.5 μL, 0.045 mmol, 0.4 equiv) in 3 mL of dry THF was stirred at 50°C for 14 h. Then, additional CuTC (21.9 mg, 0.11 mmol, 1.0 equiv), phenylboronic acid (14.1 mg, 0.11 mmol, 1.0 equiv). and 1.0 mL of dry THF were added. The reaction was stirred for another 8 h at 50°C. After the aqueous workup, the yield of the ketone (81%) was determined by proton NMR using pentamethylbenzene as an internal standard.
  • 52
    • 33846789116 scopus 로고    scopus 로고
    • THF/hexanes solvent mixtures were used to maintain a low concentration of the active Cu(I) carboxylate in solution throughout the course of the cross-coupling reaction. Cu(I) carboxylate that is not complexed to the thiol ester or to the putative palladium(II) thiolate catalytic intermediate leads to competitive destruction of the boronic acid by a Cu-mediated protodeborylation.
    • THF/hexanes solvent mixtures were used to maintain a low concentration of the active Cu(I) carboxylate in solution throughout the course of the cross-coupling reaction. Cu(I) carboxylate that is not complexed to the thiol ester or to the putative palladium(II) thiolate catalytic intermediate leads to competitive destruction of the boronic acid by a Cu-mediated protodeborylation.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.