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Conformations of bryonolic acid and its derivatives in CDCl 3 solution by 1 H and 13 C NMR spectroscopy
Author(s) -
Kamisako Wasuke,
Suwa Kiyoko,
Honda Chie,
Isoi Koichiro,
Nakai Hiroshi,
Shiro Motoo,
Machida Katsunosuke
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260251004
Subject(s) - chemistry , vicinal , steric effects , ring (chemistry) , chemical shift , cyclohexane conformation , crystallography , trigonal crystal system , nuclear magnetic resonance spectroscopy , stereochemistry , computational chemistry , molecule , crystal structure , hydrogen bond , organic chemistry
Comparison of the 1 H and 13 C 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 CDCl 3 solution depend on whether the functional groups at C‐29 are trigonal, such as COOCH 3 , or tetrahedral, such as CH 2 OH. 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.