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Volumn 70, Issue 20, 2005, Pages 8140-8147

Synthesis of β-substituted α-amino acids via Lewis acid promoted enantioselective radical conjugate additions

Author keywords

[No Author keywords available]

Indexed keywords

ADDITION REACTIONS; AMINO ACIDS; ESTERS; OLEFINS; REDUCTION; STEREOCHEMISTRY; SUBSTITUTION REACTIONS;

EID: 25444456943     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo051334f     Document Type: Article
Times cited : (44)

References (63)
  • 27
    • 25844443429 scopus 로고    scopus 로고
    • Articles in Press (doi:10.1016/j.tet.2005.07.077)
    • For a review, see: Srikanth, G. S. C.; Castle, S. L. Tetrahedron Articles in Press (doi:10.1016/j.tet.2005.07.077)
    • Tetrahedron
    • Srikanth, G.S.C.1    Castle, S.L.2
  • 42
    • 25444500904 scopus 로고    scopus 로고
    • note
    • 3B (5 equiv) also yielded recovered 1a. When this reaction was conducted in the presence of i-PrI (5 equiv), reduced product 3a was obtained in 60% yield (see the second entry of Table 1).
  • 44
    • 25444449416 scopus 로고    scopus 로고
    • note
    • 1H NMR spectra to those of 1a and 1b. The olefinic proton of the E-isomers resonates at 8.1-8.0 ppm, whereas in the Z-isomers it resonates at 7.6-7.5 ppm.
  • 46
    • 25444475686 scopus 로고    scopus 로고
    • note
    • 1H NMR spectra to that of 6a. The olefinic protons of these compounds resonate at 8.02-8.01 ppm, consistent with the chemical shifts of the corresponding protons in E-1a-c.
  • 47
    • 85010450312 scopus 로고
    • a of ethyl nitroacetate has been measured as 5.62. For a review of the chemistry of α-nitro esters, see: Shipchandler, M. T. Synthesis 1979, 666.
    • (1979) Synthesis , pp. 666
    • Shipchandler, M.T.1
  • 48
    • 25444474091 scopus 로고    scopus 로고
    • note
    • 1H NMR spectra recorded immediately after isolation of d-7a-c exhibited amide N-H signals attenuated by an amount consistent with the extent of proton incorporation at the α-position. Over time, the N-bound deuterium exchanged with protons derived from adventitious moisture and the amide signals returned to their normal levels of intensity. Attempts to block this exchange by performing radical conjugate additions on protected or tertiary amides were unsuccessful; the N-Boc derivative of 6a afforded reduction product exclusively, whereas N-PMB and N-Me versions were unreactive.
  • 61
    • 25444527659 scopus 로고    scopus 로고
    • note
    • For a discussion of the effect of molecular sieves on chiral Lewis acids, see ref 23b.
  • 62
    • 0030813703 scopus 로고    scopus 로고
    • 1H NMR spectra to those of 2b. Specifically, the α- and β-protons of the syn isomers each resonated 0.15-0.20 ppm upfield from the corresponding protons of the anti isomers, and the syn-isopropyl methine resonated ca. 0.20 ppm downfield from the anti-isopropyl methine.
    • (1997) Tetrahedron , vol.53 , pp. 16645
    • Liao, S.1    Shenderovich, M.D.2    Lin, J.3    Hruby, V.J.4


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.