Studies in the stereochemistry of 2-alkyl-3-hydroxy- and 2-alkyl-3-methoxy-butyric acids
The diastereoisomeric 3-hydroxy-2-methyl- and 3-methoxy-2-methyl-butyric acids resulting on demercuriation of mercuric acetate adducts of 2-methylbut-2-enoic acids have been studied, and their i.r., n.m.r., and mass spectrometric properties compared with those of the diastereoisomeric ethyl 2-allyl-3-hydroxy- and 3-hydroxy-2-propylbutyrates. Demercuriation of the mercuric acetate adducts of tiglic acid with sodium borohydride is found to give mixtures of the diastereoisomeric products, whereas demercuriation with hydrogen sulphide yields essentially only one of these diastereoisomers. Evidence for the configurations of these products is presented. The diastereoisomer of 3-methoxy-2-methylbutyric acid resulting on demercuriation, by means of hydrogen sulphide, of a mercuric acetate adduct of tiglic acid has been resolved via the quinine salt.