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Volumn 71, Issue 5, 2006, Pages 1879-1891

Divergence en route to nonclassical annonaceous acetogenins. Synthesis of pyranicin and pyragonicin

Author keywords

[No Author keywords available]

Indexed keywords

ALKYNYLATIONS; DESYMMETRIZATION; RACEMIC ALDEHYDE;

EID: 33644652277     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo052233k     Document Type: Article
Times cited : (40)

References (101)
  • 7
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    • note
    • The ACGs are among the most potent inhibitors of NADH-ubiquinone oxidoreductase known; see ref 2a.
  • 23
    • 33644659430 scopus 로고    scopus 로고
    • note
    • The nonclassical subgroup is defined as acetogenins bearing a THP and/or a ring-hydroxylated THF moiety.
  • 25
    • 33644660125 scopus 로고    scopus 로고
    • note
    • For further details on SAR. see refs 2a,b and references therein.
  • 30
    • 0036216970 scopus 로고    scopus 로고
    • For recent review concerning asymmetric HWE reactions see: Rein, T.; Pedersen, T. M. Synthesis 2002, 579-594.
    • (2002) Synthesis , pp. 579-594
    • Rein, T.1    Pedersen, T.M.2
  • 39
    • 0002759095 scopus 로고
    • (+)-(1S,2R,5S)-8-phenylmenthol is now commercially available. For preparation, see: Buschmann, H.; Scharf, H. D. Synthesis 1988, 827-830.
    • (1988) Synthesis , pp. 827-830
    • Buschmann, H.1    Scharf, H.D.2
  • 42
    • 33644637773 scopus 로고    scopus 로고
    • note
    • For clarity, the chiral auxiliaries used are abbreviated: R ′ (1S,2R)-nor-8-phenylmenthyl: R″ = (1R,2S,5R)-8-phenylmenthyl.
  • 43
    • 33644636450 scopus 로고    scopus 로고
    • note
    • For clarity, the chiral auxiliaries used are abbreviated: R ′ (1S,2R)-nor-8-phenylmenthyl: R″ = (1R,2S,5R)-8-phenylmenthyl.
  • 45
    • 33644651417 scopus 로고    scopus 로고
    • note
    • This trend was efficiently exploited in the hetero-Michael cyclizations of 18 and 21 as described in ref 18.
  • 46
    • 33644661687 scopus 로고    scopus 로고
    • note
    • Upon cleavage of the chiral auxiliary in the subsequent step, the relationship between the products becomes enantiomeric, thus preventing removal of the minor isomer until a further reagent controlled asymmetric transformation is carried out.
  • 51
    • 33644661245 scopus 로고    scopus 로고
    • note
    • Procedure: To a stirred solution of chloroacetate 36 (31 mg, 0.032 mmol) in 1.5 mL of toluene was added a freshly prepared solution of water (1.17 μL, 0.065 mmol) and t-BuOK (9.7 μL, 1.0 M in THF) in 0.7 mL of toluene at 0 °C. The temperature was brought to room temperature over 1 h. The reaction was then quenched by addition of phosphate buffer pH 7 and subjected to the usual workup giving the cyclisized product 29 (18.3 mg, 65%).
  • 64
    • 33644657288 scopus 로고    scopus 로고
    • note
    • To simplify the determination of the diastereoselecitivty of the addition, the saturated aldehyde 85 was used as a model.
  • 69
    • 33644656202 scopus 로고    scopus 로고
    • note
    • 47
  • 70
  • 71
    • 33644651103 scopus 로고    scopus 로고
    • note
    • This should be compared to a 54:46 (Z):(E) mixture using a 50:50 mixure of phosphonates 55 and 56; see footnote 20.
  • 72
    • 33644655090 scopus 로고    scopus 로고
    • note
    • 2OH could be recovered in 80% by bulb-to-bulb distillation of the reaction crude.
  • 75
    • 33644638193 scopus 로고    scopus 로고
    • note
    • 47
  • 80
    • 33644638046 scopus 로고    scopus 로고
    • note
    • 63
  • 85
    • 33644638623 scopus 로고    scopus 로고
    • note
    • One might speculate that the very low concentration used in this analysis would render the outcome sensitive to experimental error and impurities.
  • 88
    • 33644638926 scopus 로고    scopus 로고
    • note
    • 3N, 10.0 equiv; butenolide 77, 1.3 equiv; and aldehyde 50b, 1.0 equiv.
  • 89
    • 33644660906 scopus 로고    scopus 로고
    • note
    • 1H NMR of the reaction crude. The isomers are separable by flash but were not identified. One might expect that this cyclization could be circumvented by reversing the order of reactions, starting with elimination of 78 and then performing a diimide reduction of the product.
  • 91
    • 33644658609 scopus 로고    scopus 로고
    • note
    • 1H NMR spectrum after filtration through a short plug of silica to remove any remaining aldehyde.
  • 92
    • 33644656350 scopus 로고    scopus 로고
    • note
    • 3N, 5.0 equiv.
  • 93
    • 33644647895 scopus 로고    scopus 로고
    • note
    • For further details, see Supporting Information.
  • 95
    • 33644647445 scopus 로고    scopus 로고
    • note
    • 13C NMR (125 MHz) δ 164.1, 151.9, 128, 1, 125.3, 125.1, 123.7, 121.1, 76.3, 62.4 (qd, J = 19.6, 5.5 Hz), 62.3 (qd, J = 19.6, 5.5 Hz), 50.5, 39.5, 39.5, 33.4, (d, J = 14.4 Hz), 32.9, 30.0, 26.6, 25.8, 24.6, 22.1.
  • 96
    • 33644641486 scopus 로고    scopus 로고
    • Ph.D. Thesis, Tartu University, Estonia
    • See also: Vares, L. Ph.D. Thesis, Tartu University, Estonia, 2000.
    • (2000)
    • Vares, L.1
  • 97
    • 33644651983 scopus 로고    scopus 로고
    • note
    • Alternatively, the crude 16 obtained after filtration through a short plug of silica could be directly subjected to reduction/protective group migration. This protocol afforded 18 in 70% overall yield, based on 20.
  • 98
    • 33644638333 scopus 로고    scopus 로고
    • note
    • Due to the higher reactivity of aldehyde 50a compared to that of aldehyde 70, the reaction could be run at room temperature using standard inert techniques.
  • 100
    • 33644641058 scopus 로고    scopus 로고
    • note
    • Sealing the reaction vessel using a septum was not sufficient to prevent TMS-acetylene from escaping from the reaction.
  • 101
    • 33644654423 scopus 로고    scopus 로고
    • note
    • 19F analysis of the corresponding (+)-and (-)-MTPA derivatives.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.