ISSN:
0749-1581
Schlagwort(e):
19F spectroscopy
;
9α-Fluorosteroids
;
Proton-fluorine coupling
;
Vicinal shielding effects
;
Remote deshielding effects
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Fluorine NMR spectra of 23 9α-fluorocorticosteroid analogs established that the 9α-fluorine is subject to deshielding effects by remote structural features (A-ring olefinic unsaturation, A-ring 1α- and 2β-hydroxy and acetoxy features and D-ring 16α-methyl substitution) and to minor shielding effects by vicinal 11β-alcohol dehydrogenation and acetylation, and by B-ring olefinic unsaturation. Substitutions in the 6α-, 6β-, 16α- and 16β-positions and D-ring homoannulation do not alter the 19F chemical shift significantly. Coupling constants of the 9α-fluorine to vicinal 8β- and 11α-hydrogens are not altered appreciably by structural changes, except for introduction of a Δ6-double bond or 11β-alcohol dehydrogenation, indicating that the conformations of the tetracyclic ring system and particularly the B/C-ring junction were very similar for these 9α-fluorosteroids.
Zusätzliches Material:
1 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/mrc.1260280506
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