Co-Authors:
Glotter, E., Department of Chemistry, The Weizmann Institute of Science, Rehovoth, Israel
Weissenberg, M., Department of Chemistry, The Weizmann Institute of Science, Rehovoth, Israel
Lavie, D., Department of Chemistry, The Weizmann Institute of Science, Rehovoth, Israel
Abstract:
Cholestan-1,4-diones as well as cholest-2-en-1,4-diones in the 5α and 5β series have been synthesized in several steps from 1α-hydroxy-5α-cholest-2-ene and 1β-hydroxy-5β-cholest-2-ene. The conformation of ring A in these compounds has been analysed by NMR solvent shifts. Equilibration studies have shown that the 1,4-diones are more stable with rings A/B in the cis arrangement. In the case of the unsaturated 1,4-diones, epimerization of the 5α-isomer takes place to an extent of 95%. The increased stability of the cis A/B system is attributed to a decrease of the nonbonded interaction of the 1-carbonyl with the 11α-H. The thioketalization of some of the above ketones has also been investigated; 4-thioketals in the 5β series have been obtained and their behaviour in acidic conditions studied. © 1970.
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