Conformations of the nine-membered ring in the B-nor-5,10-secosteroids. X-ray and NMR analysis
(2005) Helvetica Chimica Acta — Vol. 88, n° 10, p. 2812-2821 (2005)
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- Abstract
- The conformations of (Z)- and (E)-5-oxo-B-nor-5,10-secocholest-1(10)-en-3 beta-yl acetates (2 and 3, resp.) were examined by a combination of X-ray crystallographic analysis and NMR spectroscopy, with emphasis on the geometry of the cyclononenone moiety. The H-1- and C-13-NMR spectra showed that the unsaturated nine-membered ring of (E)-isomer 3 in C6D6 and (D-6)acetone solution exists in a sole conformation of type B-1, which is similar to its solid-state conformation. The (Z)-isomer 2 in C6D6 CDCl3, and (D-6)acetone solution. however, exists in two conformational forms of different families, with different orientation of the carbonyl group, the predominant form (85%) corresponding to the conformation of type A, and the minor (15%) to the conformation A(2) present also in the crystalline state. In this solid-state conformations of the nine-membered ring of both compounds, the 19-Me and 5-oxo groups are 'beta'-oriented. The NMR analysis suggests that the nine-membered ring of 4 has a conformation of type C-1 in CDCl3 solution.
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Bjelakovic, M., Krstic, N., Tinant, B., Kalvoda, J., Csanadi, J., & Pavlovic, V. (2005). Conformations of the nine-membered ring in the B-nor-5,10-secosteroids. X-ray and NMR analysis. Helvetica Chimica Acta, 88(10), 2812-2821. https://doi.org/10.1002/hlca.200590221 (Original work published 2005)