4,4-Dimethyl effect (2). Syntheses, 1H- and 13C-nuclear magnetic resonance spectra, and the conformations of 6.ALPHA.- and 6.BETA.-substituted-1,1,10.BETA.-trimethyl-trans-decal-2-ones (8.ALPHA.- and 8.BETA.-substituted-4,4,10.BETA.-trimethyl-trans-decal-3-ones), models of 4,4-dimethyl-steroid- and triterpenoid-3-ketones.

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.