A new strategy for stereocontrol of cation-olefin cyclization. The first chemical emulation of the A/B-trans-9,10-syn-folding pathway of steroid biosynthesis from 2,3-oxidosqualene

Journal of the American Chemical Society

Volumn 118, Issue 47, 1996, Pages 11982-11983

  Corey, E J ^a   Wood Jr , Harold B ^a  

^a HARVARD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

STEROID;

ARTICLE; DRUG STRUCTURE; IN VITRO STUDY; REACTION ANALYSIS; STEREOCHEMISTRY; STEROIDOGENESIS; X RAY ANALYSIS;

EID: 0029902231     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja9632926     Document Type: Article

References (20)

1. (a) Johnson, W. S. Tetrahedron 1991, 47, xi.
2. (b) Abe, I.; Rohmer, M.; Prestwich, G. D. Chem. Rev. 1993, 93, 2189.
3. (a) Corey, E. J.; Virgil, S. C. J. Am. Chem. Soc. 1991, 113, 4025.
4. (b) Corey, E. J.; Virgil, S. C.; Sarshar, S. J. Am. Chem. Soc. 1991, 113, 8171.
5. (c) Corey, E. J.; Virgil, S. C.; Cheng, H.; Baker, C. H.; Matsuda, S. P. T.; Singh, V.; Sarshar, S. J. Am. Chem. Soc. 1995, 117, 11819.
6. (a) Sutherland, J. K. In Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 3, p 341.
7. (b) Taylor, S. K. Org. Prep. Proced. Intl. 1992, 24, 245.
8. (c) Corey, E. J.; Lee, J. J. Am. Chem. Soc. 1993, 115, 8873.
9. (d) Corey, E. J.; Lee, J.; Liu, D. R. Tetrahedron Lett. 1994, 35, 9149.
10. (e) Corey, E. J.; Lin, S. J. Am. Chem. Soc. 1996, 118, 8765.
11. The 1:1 mixture of E- and Z-isomers of 4 could not be separated chromatographically. Further research is planned toward the objective of the stereoselective conversion of 3 to the E-isomer of 4.
12. The methyl vinyl ether analog of 4 was not a satisfactory substrate for cyclization because the basicity of the methoxy group interfered by coordinating to the Lewis acidic reagent.
13. 1H NMR NOE data.
14. The coordinates of 7 and other X-ray data can be obtained, on request, from the Director, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, U.K.
15. The reaction barrier in cation-olefin addition is mainly due to solvent reorganization (cation desolvation-resolvation) and steric effects. In the gas phase there is essentially no barrier to the addition of the tert-butyl cation to isobutylene which is 6.5 kcal/mol exothermic at a C-C separation of 3 Å (Prof. William L. Jorgensen, Yale University, personal communication. March, 1996). For such highly exothermic (ca. 20 kcal/mol), low activation enthalpy cyclizations, an early transition state is likely and a bonding C-C distance of 3 ± 0.3 Å seems reasonable.
16. Pfau, M; Revial. G.: Guingnat, A.; d'Angelo, J. J. Am. Chem. Soc. 1985, 107, 273.
17. Minami, I.; Takahashi, K.; Shimizu, I.; Kimura, T.; Tsugi, J. Tetrahedron 1986, 42, 2971.
18. Griffith, W. P.; Ley, S. V. Aldrichimica Acta 1990, 23, 13.
19. Corey, E. J.; Noe, M. C.; Shieh, W.-C. Tetrahedron Lett. 1993, 34, 5995.
20. Stork, G.; Maldonado, L. J. Am. Chem. Soc. 1971, 93, 5286.