Synthesis and Carbon-13 Nuclear Magnetic Resonance Studies of Δ5 and Saturated 4,4-Disubstituted 3-Ketosteroids

Article abstract of DOI:10.1021/jo00319a017

A number of Δ⁵-4,4-dialkyl-3-ketosteroids were synthesized by alkylation of steroidal 4-en-3-ones via their enolate anions.Carbon-13 nuclear magnetic resonance spectra of these compounds were measured and assigned.Predicted carbon shifts show fairly good agreement with the observed values in the estrenone series.The deviations for androstenones and cholestenones were interpreted in terms of conformational changes in the steroid skeleton which arise from nonbonded 1,5-interactions (δ-effect) between the 19-methyl and the 4,4 substituents.Comparison of the carbon shifts for 4,4-dimethyl-3-ketosteroids with the appropriate Δ⁵derivatives did not indicate any "conformational transmission" in the latter compounds.The observed carbon shift differences for C-14 seem to arise solely from the presence of the 19-methyl group.