Carbon-13 NMR studies in the polycyclic hydrocarbon series. A new method for the identification of carbons α to a carbonyl group. Complete assignment of the 13C NMR spectra of several cis-decalins, cis-decalones, cis-hydrindanones and 13α,14α- and 13β,14β-steroids
✍ Scribed by J. C. Gramain; J. C. Quirion
- Publisher
- John Wiley and Sons
- Year
- 1986
- Tongue
- English
- Weight
- 711 KB
- Volume
- 24
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
A new 13C N M R method based on solvent effects allows the identification of carbon atoms a to a carbonyl group. With a simple change in solvent from CDCl, to CDC1,-dioxane (1:4), the -C absorption for all carbons except those a to the carbonyl group in the compounds under study were displaced to lower field by 0.2-0.5 ppm. The a-carbon absorptions either remained unchanged or were shited to higher field by cu 0.1 ppm. The validity of the method has been checked on compounds with fully assigned -C NMR spectra (puns-decalones and steroids). Moreover, no modification of these solvent shifts due to the presence of other common functional groups (double bond or OH) was observed. This new technique, together with existing 'classical' methods ('off-resonance' spectra, substituent effects) enables the complete interpretation of the 13C N M R spectra of five cis-decalins and cis-decalones to be made. The spectra of three cis-hydrindanones which have not been previously described were also fully interpreted.
The same method allows the complete spectral assignment of the uC N M R spectra of six steroids of unnatural configuration in the 13a,14a-and 13f3,14fi-androstane series, for which no data were previously available.
KEY WORDS 13C NMR Carbons (Y to Carbonyl Group cis-Decalins cis-Decalones cis-Hydrindanones 13a, 14aand 138,14j3-Steroids