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The conformation of ring A in 4,4-dimethyl-3-keto-steroids

✍ Scribed by Norman L. Allinger; Margaret A. DaRooge

Publisher
Elsevier Science
Year
1961
Tongue
French
Weight
258 KB
Volume
2
Category
Article
ISSN
0040-4039

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✦ Synopsis

THE ground state oouformations of the steroid ring systems are in general securely looked in potential wells, can vary but little, and are for the most part well understood. In a 4,4-dimethyl-3-keto-5gC-steroid (I) however, there is reason to question whether or not ring A will be in the standard chair form, aud the answer to this question is of interest because of the widespread oocurrenoe of thie type of structure in nature. Recently, numerioal value8 have been reported for the enthalpies of two quantities related to this question, namely the 1,3-diaxial dimethyl interaction, 4 3.7 koal/mole, and the chairjboat transformation of a cyclohexsnone,5 2.8 koal/mole. Aotually other interactions must be considered, but a first approximation would seem to indicate that ring A in I might be more comfortable in the boat form than in the undeformed (or slightly deformed) chair (II).

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