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Volumn 4, Issue 5, 2002, Pages 859-962

Studies toward the total synthesis of garsubellin A: A concise synthesis of the 18-epi-tricyclic core

Author keywords

[No Author keywords available]

Indexed keywords

CHOLINE ACETYLTRANSFERASE; FUSED HETEROCYCLIC RINGS; GARSUBELLIN A; LACTONE; TERPENE;

EID: 0037035006     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol0255965     Document Type: Article
Times cited : (64)

References (34)
  • 7
    • 0042042194 scopus 로고    scopus 로고
    • Preliminary results indicated the feasibility of this idea (see the following scheme). Absolute configurations of the cyanohydrins are temporarily assigned from the preceding examples (ref 4b). (equation presented)
    • Preliminary results indicated the feasibility of this idea (see the following scheme). Absolute configurations of the cyanohydrins are temporarily assigned from the preceding examples (ref 4b). (equation presented)
  • 8
    • 0000569855 scopus 로고
    • Other isomers emerged through a retro aldol-aldol sequence, if the reaction temperature was raised to slightly over -70°C or if there was a long reaction time (> 1 h). For an organocuprate conjugate addition - threo-selective aldol reaction, see: Heng, K. K.; Smith R. A. J. Tetrahedron 1979, 35, 425-435.
    • (1979) J. Tetrahedron , vol.35 , pp. 425-435
    • Heng, K.K.1    Smith, R.A.2
  • 9
    • 0000477891 scopus 로고
    • 2AlCl) failed. For Lewis base-catalyzed cyanosilylation of aldehydes, see: (a) Evans, D. A.; Truesdale, L. K. Tetrahedron Lett. 1973, 49, 4929-4932.
    • (1973) Tetrahedron Lett. , vol.49 , pp. 4929-4932
    • Evans, D.A.1    Truesdale, L.K.2
  • 11
    • 0042042195 scopus 로고    scopus 로고
    • The diastereomers of 15 or 19 could be separated by column chromatography. We continued the synthesis as a diatereo-mixture, because the stereochemistry of C-4, -6, and -27 disappeared at the later stage
    • The diastereomers of 15 or 19 could be separated by column chromatography. We continued the synthesis as a diatereo-mixture, because the stereochemistry of C-4, -6, and -27 disappeared at the later stage.
  • 12
    • 0041540925 scopus 로고    scopus 로고
    • Reactions using a normal higher order cuprate (CuCN/MeLi = 1/2) gave unpredictable results. On the other hand, reactions performed under the conditions described in the text were completely reproducible
    • Reactions using a normal higher order cuprate (CuCN/MeLi = 1/2) gave unpredictable results. On the other hand, reactions performed under the conditions described in the text were completely reproducible.
  • 14
    • 0041540926 scopus 로고    scopus 로고
    • The relative configuration was determined by X-ray analysis
    • The relative configuration was determined by X-ray analysis.
  • 15
    • 0042042192 scopus 로고    scopus 로고
    • These preliminary studies were conducted with the diastereomerically pure compound
    • These preliminary studies were conducted with the diastereomerically pure compound.
  • 16
  • 17
    • 0042042191 scopus 로고    scopus 로고
    • The possibility that the reaction proceeded through a dianion could be excluded because the reaction using 1.2 equiv of KO′Bu under the optimized conditions (see below) gave 23 + 24 in 43% yield
    • The possibility that the reaction proceeded through a dianion could be excluded because the reaction using 1.2 equiv of KO′Bu under the optimized conditions (see below) gave 23 + 24 in 43% yield.
  • 18
    • 0041540924 scopus 로고    scopus 로고
    • The structure of 23 was unequivocally determined by X-ray crystallography. See Supporting Information for details
    • The structure of 23 was unequivocally determined by X-ray crystallography. See Supporting Information for details.
  • 19
    • 0042042193 scopus 로고    scopus 로고
    • Direct formation of the lithium enolate with LiO′Bu failed due to the lower basicity of the base
    • Direct formation of the lithium enolate with LiO′Bu failed due to the lower basicity of the base.
  • 20
    • 0043043882 scopus 로고    scopus 로고
    • Preliminary studies to reverse the stereoselectivity of this one-pot cyclization revealed that employing a cyclic carbonate for the protecting group of the diol instead of the acetonide gave an ca. 1:1 mixture of diastereomers. Although the origin of the high stereoselectivity in the case of acetonide-protected 19 is not clear, coordination of the 18-oxygen atom to the lithium atom of the enolate might fix the substrate conformation to block the entry of the electrophile from the β-side
    • Preliminary studies to reverse the stereoselectivity of this one-pot cyclization revealed that employing a cyclic carbonate for the protecting group of the diol instead of the acetonide gave an ca. 1:1 mixture of diastereomers. Although the origin of the high stereoselectivity in the case of acetonide-protected 19 is not clear, coordination of the 18-oxygen atom to the lithium atom of the enolate might fix the substrate conformation to block the entry of the electrophile from the β-side.
  • 21
    • 0043043884 scopus 로고    scopus 로고
    • These results indicated that the observed high stereoselectivity was derived from the C-18 configuration
    • These results indicated that the observed high stereoselectivity was derived from the C-18 configuration.
  • 23
    • 0000533773 scopus 로고    scopus 로고
    • We tried dimethylphenylsilyl, (diethylamino)diphenylsilyl, and dimethyl(o-methoxy)phenylsilyl groups, in addition to the pentamethyldisilyl group. The former two silyl groups could be introduced to 23 by conjugate addition in high yields (>90%); however, later conversions were unsuccessful. The third one (Lee, T. W.; Corey, E. J. Org. Lett. 2001, 3, 3337-3339) did not produce the conjugate adduct to 23.
    • (2001) Org. Lett. , vol.3 , pp. 3337-3339
    • Lee, T.W.1    Corey, E.J.2
  • 28
    • 84889488515 scopus 로고
    • Suginome, M.; Matsunaga, S.; Ho, Y. Synlett 1995, 941-942. Reaction under normal Tamao-oxidation conditions failed, possibly due to the instability of the intermediate alcohol under basic conditions.
    • (1995) Synlett , pp. 941-942
    • Suginome, M.1    Matsunaga, S.2    Ho, Y.3
  • 31
    • 0042542998 scopus 로고    scopus 로고
    • The structure of 4 was unequivocally determined by X-ray crystallography. See the Supporting Information for details
    • The structure of 4 was unequivocally determined by X-ray crystallography. See the Supporting Information for details.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.