STEREOCHEMICAL STUDIES OF 1,2-DI(THIO)ACETAMIDOCYCLOHEXANES AND THEIRN,N-DIMETHYL DERIVATIVES BY NMR AND CD SPECTROSCOPY AND BY MOLECULAR MECHANICS CALCULATIONS

The configurations and conformations of cis- and trans- 1,2-di (thio) acetamidocyclohexane and their N,N'-dimethyl derivatives have been stu died by H-1 and C-13 NMR spectroscopy, using chemical shifts and coupl ing constants, difference NOE H-1 NMR spectra and 2D H-1-C-13 NMR corr elation spectra. For the trans compounds, the Z,Z configuration of the (thio)amide groups with equatorial (thio)acetamido groups was found t o be strongly preferred. For the cis compounds, E,Z configurations of the (thio)amide groups with axial E and equatorial Z groups were found to be preferred. Empirical force-held calculations with the MM2(91) f orce field led to predictions for the most stable configurations and c onformations, mostly in very good agreement with those obtained by NMR spectroscopy. CD spectra recorded for the trans-(R,R)-N-methyl compou nds in acetonitrile solution agreed well with those calculated on the basis of geometries from force-field calculations. The CD spectra calc ulated for the trans-(R,R)-NH- compounds and for the cis-monothio comp ounds showed poor agreement with the experimental spectra.