Determination of the enantiomeric purity of the phytoalexins spirobrassinins by 1H NMR using chiral solvation

A simple and inexpensive method for enantiomeric discrimination of the phytoalexins spirobrassinin (1), 1-methoxyspirobrassinin (2) and synthetic analog 1-methylspirobrassinin (6) using the chiral solvating agent 2,2,2-trifluoro-1-(9-anthryl)ethanol in C6D6 is described. Using this method the enantiomeric composition of each sample can be determined accurately by 1H NMR and the compounds can be recovered readily by chromatography.