NMR SPECTROSCOPIC CHARACTERIZATION OF Z-E ISOMERS OF CYCLODODECA-1,5,9-TRIENE

The four Z-E isomers of cyclododeca-1,5,9-triene were examined by C-13 NMR spectroscopy. The vicinal H-1-H-1 coupling constants of the olefi nic protons were used to determine the stereochemistry at the double b onds. For the symmetrically substituted -CH=CH- fragments (chemically equivalent H atoms) this parameter was obtained from the C-13 NMR mult iplets which are observed in H-1 continuous-wave off-resonance C-13 NM R experiments. The precise assignment of the H-1 and C-13 chemical shi fts, in particular for the Z,Z,E and Z,E,E isomers, was possible on th e basis of off-resonance measurements in combination with C-13/H-1 het eronuclear correlated and H-1/H-1-COSY-45 2D experiments.