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Volumn 70, Issue 26, 2005, Pages 10619-10637

Total synthesis of guanacastepene A: A route to enantiomeric control

Author keywords

[No Author keywords available]

Indexed keywords

AMINO ACIDS; CHEMICAL BONDS; CONDENSATION; KETONES; STEREOCHEMISTRY; SYNTHESIS (CHEMICAL);

EID: 29944441120     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo051470k     Document Type: Article
Times cited : (72)

References (91)
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    • For other syntheses of structures which connected with late compounds described herein, thus constituting formal syntheses, see: (a) Shi, B.; Hawryluk, N. A.; Snider, B. B. J. Org. Chem. 2003, 68, 1030.
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    • (b) Boyer, F.-D.; Hanna, I.; Ricard, L. Org. Lett. 2004, 6, 1817. For other stimulating work in the guanacastepene series, cf. inter alia:
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    • Iodo-1-pentene was prepared by treatment of 5-bromo-1-pentene with 3.0 equiv of NaI in refluxing acetone for 6 h as described previously: Padwa, A.; Kamigata, N. J. Am. Chem. Soc. 1977, 99, 1871.
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    • note
    • Snider and Hawryluk also observed only formation of a 5,5-fused ring system in their attempts to perform a direct aldol with a similar substrate. See ref 4a.
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    • For an early example of a similar oxidative transposition, see: Büchi, G.; Egger, B. J. Org. Chem. 1971, 36, 2021.
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    • For acid catalyzed and thermal rearrangements of enol ether epoxides, cf. inter alia: (a) Zhu, Y.; Shu, L.; Tu, Y.; Shi, Y. J. Org. Chem. 2001, 66, 1818.
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    • note
    • The thermolysis study described above for the 5-α series has been separately performed on the equivalent substrate in the 5-β series (see 62), which corresponds to the guanacastepene stereochemistry. In studies with this substrate, there appears to be a preference for formation of the 13-β acetoxy product (74) over the 13-αa acetoxy product (13-epi-74). The ratio of 74 to 13-epi-74 was approximately 2.3: 1.
  • 78
    • 29944435465 scopus 로고    scopus 로고
    • note
    • The X-ray shows that, while the first carbon of the isopropyl group is, indeed, β, the geminal dimethyls are α-disposed. Therefore, in addition to confirming the stereochemical assignment described above, the X-ray also rationalizes why attack of oxidizing agents occurs primarily from the β-face of the molecule. We and others continue to investigate this matter.
  • 81
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    • note
    • An authentic sample is no longer available for comparison (J. Clardy, personal communication). In fact, at the present time chemical synthesis is the only source of this compound.
  • 82
    • 29944436640 scopus 로고    scopus 로고
    • note
    • 1H NMR spectra of the natural product. We are grateful to Prof. Jon Clardy and Dr. Sean F. Brady for providing detailed NMR spectra of natural guanacastepene A.


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