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. (author)