ISSN:
0749-1581
Keywords:
Conformation
;
D:C-friedoolean-8-enes
;
Molecular mechanics calculation
;
1H and 13C NMR
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Comparison of the 1H and 13C chemical shift data of bryonolic acid (D : C-friedoolean-8-en-3β-ol-29-oic acid) and its derivatives (13 species) revealed that the conformational features of these compounds in CDCl3 solution depend on whether the functional groups at C-29 are trigonal, such as COOCH3, or tetrahedral, such as CH2OH. In order to study the conformational features of these two groups of compounds, vicinal coupling constants between the protons on the E rings of the methyl ester of D : C-friedoolean-8-en-29-oic acid, D : C-friedoolean-8-en-29-oic and its acetate were measured. Comparison of the results with the steric geometries to be expected from the molecular mechanics calculation for the E-ring moieties of these derivatives in the S form (D-E rings: boat-boat form) and the F form (D-E rings: chair-chair form) led to the conclusion that the compounds having a trigonal functional group at C-29 mainly adopt the S form, and those having a tetrahedral functional group at C-29 are present as mixtures of the S and F form in equilibrium in the solutions.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260251004
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