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Carbon-13 NMR of tertiary fluorosteroids as a stereochemical probe

✍ Scribed by Shlomo Rozen; Giora Ben-Shushan

Publisher
John Wiley and Sons
Year
1985
Tongue
English
Weight
272 KB
Volume
23
Category
Article
ISSN
0749-1581

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✦ Synopsis

The -C NMR spectra of tertiary fluorinated steroids possessing no functional groups in the vicinity of the fluorine have been measured. All a-and @-carbons are deshielded by the fluorine atom. The y-carhons, however, are divided into two groups. The carbons gauche to the fluorine atom are all shielded by 1-8 ppm, whereas the y-carbons anti to the halogen are all deshielded by 2-5 ppm. Apart from the a-carbons, which have coupling constants of 170-180 Hz, all @-carbons are also coupled to the fluorine with a 2J(CF) value of approximately 20Hz. The y-carbons gauche to the fluorine have a very small coupling constant (usually 0-3 Hz), while the anti y-carbons are split by the fluorine by 6-8 Hz. Both chemical shifts and coupling constants can be used for the stereochemical evaluation of fluorosteroids.

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