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Epoxidation-induced shifts in the carbon-13 NMR spectra of steroids: Lanostane derivatives

✍ Scribed by Jacek Martynow; Zdzisław Paryzek

Publisher
John Wiley and Sons
Year
1989
Tongue
English
Weight
463 KB
Volume
27
Category
Article
ISSN
0749-1581

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✦ Synopsis

The ' ' C chemical shifts of triterpenoidal olefins and epoxides related to lanosterol are described and discussed. The epoxide function located in the central part of the tetracyclic steroidal skeleton allows the evaluation of epoxidation-induced shifts (EIS) for several carbons. The most characteristic and valuable for stereochemical assignments are the EIS values for y-carbons C-1, (2-5, C-12, C-19 and C-28 in 8a,9a-epoxides, and C-1 and C-19 in 9a,lla-epoxides. The C-a effect (EIS -55 to -79 ppm) is found to be susceptible to minor conformational distortions of the molecular framework. Characteristic signals are discussed in terms of their predictive value for each group of analysed compounds. KEY WORDS "C NMR Epoxidation-induced shifts Triterpenoidal olefins and epoxides Lanosterol * Tetracyclic Triterpenes, Part XI. For Part X, see Ref. 32.

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