Formation of the B ring in steroids and hopanoids from squalene

European Journal of Organic Chemistry

Volumn , Issue 10, 2004, Pages 2239-2242

  Hess Jr , B Andes ^a  

^a VANDERBILT UNIVERSITY   (United States)

Author keywords

Conformational analysis; Density functional calculations; Reaction mechanisms; Steroids; Terpenoids

Indexed keywords

HOPANOID; SQUALENE; STEROID;

ARTICLE; CHEMICAL ANALYSIS; CHEMICAL REACTION; CONFORMATION; CYCLIZATION; DENSITY FUNCTIONAL THEORY; REACTION ANALYSIS; SYNTHESIS;

EID: 4544238011     PISSN: 1434193X     EISSN: None     Source Type: Journal    
DOI: 10.1002/ejoc.200300684     Document Type: Article

References (15)

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8. [8]) with the Lee-Yang-Parr correlation function (ref.[9] and the 6-31G* basis set (ref.[10] were employed. All relative energies given in the figures include zero-point energy corrections. Unless otherwise specified in the text, IRC calculations were performed at the SCF/3-21G level.
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12. Cartesian coordinates, imaginary frequencies for transition structures and energies may be found in the Supporting Information for all structures reported here (for Supporting Information see also the footnote on the first page of this article).
13. K. B. Wiberg, J. D. Hammer, H. Castejon, W. F. Bailey, E. L. DeLeon, R. M. Jarret, J. Org. Chem. 1999, 64, 2085-2095.
14. J. L. Margrave, J. M. Frisch, R. G. Bautista, R. L. Clarke, W. S. Johnson, J. Am. Chem. Soc. 1963, 85, 546-548. While they did not report this particular energy difference, it can easily be obtained from their data. They were more interested in obtaining the energy difference between chair and boat cyclohexane. This agreement provides additional support for the choice of the DFT method for the calculations reported here.
15. Note added in proof (March 23, 2004): Schulz has recently published the X-ray structure of 2-azasqualene cocrystallized with squalene-hopene cyclase (D. J. Reinert, G. Balliano, G. E. Schulz, Chem. Biol. 2004, 11, 121-126). Examination of this crystal structure suggests that indeed the enzyme "holds" the squalene in the proper conformation for the A- and B-ring formation to be a concerted process.