Fluorine NMR spectra of some 9α‐fluorosteroids

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 19 F 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 Δ 6 ‐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.