Chiral silylation reagents: determining configuration via NMR-spectroscopic coanalysis.

[structure: see text]Derivatization with (+)- and (-)-chloromenthoxydiphenylsilane was used to determine the absolute configuration of the insect defensive agent pinoresinol (1). Although the (1)H NMR chemical shift differences of the resulting two diastereomers are small, (1)H NMR spectroscopy provided for the unambiguous assignment of the natural product's configuration. For this purpose, a new approach involving NMR spectra of mixtures of diastereomers was used. Our method resembles coinjecting mixtures of samples of known and unknown configuration in GC and HPLC.