Analysis of 1H and 13C nuclear magnetic resonance spectra of spathulenol by two-dimensional methods

Abstract

Several two-dimensional n.m.r. (2D-n.m.r.) methods have been used for the structural analysis of spathulenol, a sesquiterpene alcohol from the peel oil of Citrus junos Tanaka. First, ¹³C resonances were classified into those due to CH, CH₂, CH₃, and quaternary carbon by INEPT. Next, ¹H–¹³C shift-correlated 2D-n.m.r. was used to assign the pairs of directly bonded ¹H and ¹³C nuclei. Finally, ¹H shift-correlated 2D-n.m.r. was employed to study the network of spin couplings in the molecule. From these data, the skeletal structure of spathulenol was determined. Finally, n.O.e.-correlated 2D-n.m.r. and the n.O.e. difference method were applied to determine the three-dimensional structure of spathulenol and to achieve complete assignment of ¹H and ¹³C resonances.