Absolute configuration and enantiomeric composition of partially resolved mandelic, atrolactic and lactic acids by ¹H NMR of their (S)-2-methylbutyl esters

The mandelic, atrolactic and lactic acid esters of the (S)-2-methyl-1-butanol were examined as diastereomeric derivatives for the stereochemical analysis of the mentioned acids by ¹H nuclear magnetic resonance (NMR) at 300 MHz. The diastereomeric esters showed distinctive signals in the methylenic absorption range (O-CH2-CH) of the alcoholic moieties. By spectral analysis at this region, absolute configurations were attributed, chemical shifts of the correspondent pro-(R) and pro-(S) hydrogens from the methylene group of the alcohol moiety were assigned and enantiomeric compositions were determined for the original partially resolved acids.