Analysis of H-1 and C-13 NMR spectra of cis- and trans-10-substituted decal-2-ones by 2D NMR techniques

The H-1 and C-13 NMR chemical shift assignments of 10-substituted decal-Zon es, cis (H, CH3 and CO2CH3) and trans (H, CH3, OH and CO2C2H5) were based o n 2D COSY and HETCOR experiments, supported by selective spin decoupling ex periments, The discrimination between the ris and the trans conformations w as ruled out on the basis of the J(1a,9) magnitudes related to dihedral ang les (Karplus rule) and also on the C-13 Shielding values of C-4 of the cis compounds, which are much more shielded than those of the trans counterpart s. The best and fastest criterion of differentiation between cis and trans conformers is the constant appearance in the C-13 PND spectra of the cis se ries of some signals of broadened linewidth and low intensity, essentially C-4, C-5 and C-7, a clue to site exchange processes; the trans counterparts showed only sharp signals because of their existence as a single conformat ion. Copyright (C) 2000 John Wiley & Sons, Ltd.