Enantiomeric differentiation of terpenic olefins by carbon-13 NMR using chiral binuclear shift reagents

A study of the enantiomeric differentiation of chiral olefinic terpenes by C-13 NMR using binuclear shift reagents is reported. The influence of the [binuclear complex]/[substrate] molar ratio on the chemical shifts and the enantiomeric splittings was investigated with six olefinic substrates. For each compound, a distance-dependent deshielding effect was observed on all nuclei except on the less substituted sp(2) carbon. The enantiomeric differentiation was observed on a large number of carbons of each substrate and was principally attributed to the difference in geometry between the diastereoisomeric complexes. This technique was successfully applied to the enantiomeric differentiation of furanodiene, a sesquiterpene with asymmetry due to its conformational rigidity. Copyright (C) 2001 John Wiley & Sons, Ltd.