4, 4-Dimethyl Effect (2). Syntheses, ¹H- and ¹³C-Nuclear Magnetic Resonance Spectra, and the Conformations of 6α- and 6β-Substituted-1, 1, 10β-trimethyl-trans-decal-2-ones (8α- and 8β-Substituted-4, 4, 10β-trimethyl-trans-decal-3-ones), Models of 4, 4-Dimethyl-steroid- and Triterpenoid-3-ketones

Abstract

A set of 6α- and 6β-(hydroxy, acetoxy, and p-bromobenzoyloxy)-1, 1, 10β-trimethyl-trans-decal-2-ones was synthesized in an unequivocal manner, and the ¹H-nuclear magnetic resonance (NMR) spectra, TH effect (ASIS shift on continuously changing the solvent from chloroform-d to benzene-d₆), and ¹³C-NMR spectra of these compounds are discussed in relation to the conformations of ring A. In solution, ring A of the 6β-derivatives was shown to be more distorted (flattened) than that of 6α-derivatives. This was also true in the crystalline state as determined by X-ray analyses of their p-bromobenzoates. The TH effect was found to reflect sensitively small conformational changes in ring A.