An experimental/theoretical approach to determine the optical purity and the absolute configuration of endo- and exo-norborn-5-en-2-ol using mandelate derivatives

The O-acetylmandelates and mandelates of endo- and exo-norborn-5-en-2-ol were prepared, both as a mixture and also as separate diastereomers. 1H NMR spectroscopy of these derivatives was efficiently used to determine the enantiomeric ratios and to predict the absolute configuration of the alcohols. Theoretical calculations were performed to locate the predominant conformations of the mandelate derivatives and GIAO 1H NMR Boltzmann-weighted average chemical shifts were computed, correctly reproducing the experimental δ and Δδ values.