Determination of the enantiomeric excesses of chiral acids by 19F NMR studies of their esters deriving from (R)-(+)-2-(trifluoromethyl)benzhydrol

15 Chiral acids were esterified with optically pure (R)-(+)-2-(trifluoromethyl)benzhydrol (R)-(+)- 1 , a readily available reagent. With respect to the carboxy group, the stereogenic centre is in the β position in the case of the acids 5a–10a and 12a–16a , and in the α position in the case of the acids 17a–20a . The diastereomeric excesses of the corresponding esters 5b–10b and 12b–20b , respectively, were easily determined by means of 19 F NMR. These d.e. values were in very good agreement with the e.e. values of the corresponding acids when the latter were known compounds.