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Volumn 127, Issue 51, 2005, Pages 18054-18065

Use of the intramolecular heck reaction for forming congested quaternary carbon stereocenters. Stereocontrolled total synthesis of (±)-gelsemine

Author keywords

[No Author keywords available]

Indexed keywords

ALCOHOLS; REACTION KINETICS; STEREOCHEMISTRY; SUBSTITUTION REACTIONS; SYNTHESIS (CHEMICAL);

EID: 29844449086     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja055711h     Document Type: Article
Times cited : (116)

References (134)
  • 3
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    • Manske, R. H. F., Ed.; Academic Press: New York
    • For general reviews of Gelsemium alkaloids, see: (a) Saxton, J. E. In The Alkaloids; Manske, R. H. F., Ed.; Academic Press: New York, 1965; Vol. 8, pp 93-117.
    • (1965) The Alkaloids , vol.8 , pp. 93-117
    • Saxton, J.E.1
  • 4
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    • Manske, R. H. F., Ed.; Academic Press: New York
    • (b) Bindra, J. S. In The Alkaloids; Manske, R. H. F., Ed.; Academic Press: New York, 1973; Vol. 14, pp 83-121.
    • (1973) The Alkaloids , vol.14 , pp. 83-121
    • Bindra, J.S.1
  • 5
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    • Brossi, A., Ed.; Academic Press: San Diego
    • (c) Liu, Z.-J.; Lu, R.-R. ibid; Brossi, A., Ed.; Academic Press: San Diego, 1988; Vol. 33, pp 83-140.
    • (1988) The Alkaloids , vol.33 , pp. 83-140
    • Liu, Z.-J.1    Lu, R.-R.2
  • 7
    • 77956812175 scopus 로고    scopus 로고
    • Cordell, G. A., Ed.; Academic Press: New York
    • (e) Takayama, H.; Sakai, S.-J. In The Alkaloids; Cordell, G. A., Ed.; Academic Press: New York, 1997; Vol. 49, pp 1-78.
    • (1997) The Alkaloids , vol.49 , pp. 1-78
    • Takayama, H.1    Sakai, S.-J.2
  • 49
    • 29844433484 scopus 로고    scopus 로고
    • note
    • See the preceding paper in this journal.
  • 50
    • 0012857368 scopus 로고    scopus 로고
    • For a comprehensive review of the intramolecular Heck reaction, see: (a) Link, J. T. Org. React. 2002, 60, 157-534.
    • (2002) Org. React. , vol.60 , pp. 157-534
    • Link, J.T.1
  • 51
    • 0032139353 scopus 로고
    • For reviews of the utility of intramolecular Heck reactions in complex molecule construction, see: (b) Link, J. T.; Overman, L. E. Chemtech 1988, 28, 19-26.
    • (1988) Chemtech , vol.28 , pp. 19-26
    • Link, J.T.1    Overman, L.E.2
  • 52
    • 29844447151 scopus 로고    scopus 로고
    • Diederich, F.; Stang, P. J., Eds.; VCH: Weinheim
    • (c) Overman, L. E.; Link, J. T. In Cross Coupling Reactions; Diederich, F.; Stang, P. J., Eds.; VCH: Weinheim; 1998; pp 231-269.
    • (1998) Cross Coupling Reactions , pp. 231-269
    • Overman, L.E.1    Link, J.T.2
  • 54
    • 29844458226 scopus 로고    scopus 로고
    • note
    • At the time there was only a single example of successful intramolecular Heck cyclization of a tetrasubstituted double bond.9a Even today, despite the recent intense investigations in this area, there are only a few examples of intramolecular Heck cyclizations of tetrasubstituted olefins, most from various investigations in our laboratories.25a
  • 56
    • 29844456954 scopus 로고    scopus 로고
    • note
    • The analogous iodo amide can be prepared by a two step sequence, involving initial palladium-catalyzed carbonylation of 8 in methanol27 followed by aminolysis of the resulting methyl ester with the dimethyl-aluminum amide of 2-iodoaniline.
  • 57
    • 29844449734 scopus 로고    scopus 로고
    • note
    • Similar success in this Heck cyclization was observed when the amide protecting group was a benzyl or methoxymethyl group. The iodide analogue of 1Oa cyclized with similar low stereoselectivity.
  • 58
    • 29844458354 scopus 로고    scopus 로고
    • note
    • 1H NMR spectrum of the oxindole isomer that places the carbonyl group proximal to C19 than in its epimer. For example, for epimers 11a/11b this signal is seen at 6.7 ppm, whereas it is seen at 6.2 ppm in isomers 12a/12b.
  • 59
    • 29844454156 scopus 로고    scopus 로고
    • note
    • In a preliminary description of these studies,9d these conditions were inappropriately described as "ligandless"; however, dba is likely bound to palladium during the Heck insertion sequence.32
  • 61
    • 29844452971 scopus 로고    scopus 로고
    • note
    • These conditions were employed by Speckamp and Hiemstra for construction of the spirooxindole in their early synthesis of (±)-gelsemine.18
  • 67
    • 0000573166 scopus 로고
    • Wiley: New York; Collect.
    • (d) White, E. H. Organic Syntheses; Wiley: New York, 1973; Collect. Vol. V, pp 336-339.
    • (1973) Organic Syntheses , vol.5 , pp. 336-339
    • White, E.H.1
  • 70
    • 29844452824 scopus 로고    scopus 로고
    • note
    • 4 resulted in unidentifiable products.
  • 73
    • 29844456468 scopus 로고    scopus 로고
    • note
    • The configuration of the nitrile substituent of 18 and 30 was determined by correlating the coupling constants predicted by the Karplus-Conroy equation with the observed coupling constants. In 18 the dihedral angle between the hydrogens at C16 and C5 is ∼90° and that between the hydrogens at C16 and C15 is ∼15°, so a doublet with a 7 Hz coupling constant is predicted; the observed coupling is 7.2 Hz. Likewise for 30, the dihedral angle between the hydrogens at C16 and C5 is ∼30° and that between the hydrogens on C16 and C15 is approximately 90°, so a doublet with a 4 Hz coupling constant is predicted; the observed coupling is 4.2 Hz.
  • 74
    • 29844433179 scopus 로고    scopus 로고
    • note
    • A related epimerization was employed by Fukuyama and Liu in their synthesis of (±)-gelsemine.20
  • 75
    • 29844438438 scopus 로고    scopus 로고
    • Ph.D. Dissertation, University of California, Irvine
    • For a detailed account of these studies, see: Old, D. W. Ph.D. Dissertation, University of California, Irvine, 1997.
    • (1997)
    • Old, D.W.1
  • 76
    • 0001302486 scopus 로고
    • For reviews of diastereoselective protonations, see: (a) Zimmerman, H. E. Acc. Chem. Res. 1987, 20, 263-268.
    • (1987) Acc. Chem. Res. , vol.20 , pp. 263-268
    • Zimmerman, H.E.1
  • 77
    • 0001129994 scopus 로고
    • (b) Fehr, C. Chimia 1991, 45, 253-261.
    • (1991) Chimia , vol.45 , pp. 253-261
    • Fehr, C.1
  • 80
    • 29844453146 scopus 로고    scopus 로고
    • note
    • Several examples of electrophile-promoted cyclization of the oxindole and vinyl groups of gelsemine were encountered during early degradation studies.3a
  • 100
    • 29844438868 scopus 로고    scopus 로고
    • note
    • The Hart total synthesis of (±)-21-oxogelsemine also features a base-promoted epimerization of a spirocyclic oxindole intermediate.
  • 101
    • 29844437459 scopus 로고    scopus 로고
    • note
    • We examined also, without success, opening the methyl aziridinium ion derived from 46 with a variety of one-carbon nucleophiles.
  • 117
    • 29844439182 scopus 로고    scopus 로고
    • note
    • Trapping the resulting enolate with N-phenyl- bis(trifluoromethanesulfonimide) was successful but gave inconsistent yields.
  • 119
    • 29844453995 scopus 로고    scopus 로고
    • note
    • At this point, it is unclear why stereoselection in the Heck cyclization varies with the nature of the β-substituent.
  • 127
    • 29844445366 scopus 로고    scopus 로고
    • note
    • In product 73, an NOE is observed between the cyclohexyl proton at C3, the vinyl proton at C19, and the aromatic proton at C9. These NOEs are consistent with the cyclohexyl ring of 73 existing in a twist boat conformation.
  • 129
    • 29844453843 scopus 로고    scopus 로고
    • note
    • The yield of the largest scale reaction we conducted of each step was used in this calculation. For the intramolecular Heck reaction of 68 an average yield of 69% was used as this reaction was only carried out on one scale.
  • 130
    • 29844437585 scopus 로고    scopus 로고
    • note
    • The first step of our gelsemine synthesis is a Diels-Alder reaction of a 1,3-cyclohexadiene with methyl acrylate.24 As chiral auxiliaries for acrylate dienophiles have been developed and much progress in asymmetric catalysis of Diels-Alder reactions has been recorded, it would appear likely that an enantioselective version of the opening moves of our gelsemine synthesis could be developed.85
  • 131
    • 0342360660 scopus 로고
    • For selected reviews of asymmetric Diels-Alder reactions, see: (a) Oh, T.; Reilly, M. Org. Prep. Proced. Int. 1994, 26, 129-158.
    • (1994) Org. Prep. Proced. Int. , vol.26 , pp. 129-158
    • Oh, T.1    Reilly, M.2


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.