1H-nuclear magnetic resonance determination of the enantiomeric purity of aliphatic primary amines, β-aminoalcohols, β-diamines and α-amino-acids with 1R-(-)-myrtenal:: scope and limitations

1R-(-)-myrtenal was tested as a chiral derivatising agent for the determination of the enantionteric purity of aliphatic primary amines, beta-aminoalcohols, beta-diamines and alpha-amino-acids. Derivatisation procedure consists in mixing one equivalent each of the amine and 1R-(-)-myrtenal directly into the nuclear magnetic resonance (NMR) tube before addition of the appropriate deuterated solvent and, for alpha-amino-acids, one equivalent of NaOH was added to neutralise the acidic function. Diastereoisomeric imines were completely formed after 12 It and analysed by H-1-NMR except for N-methyl beta-diamines for which imidazolidines were obtained. The method gave satisfactory results only for alpha- and beta-arylalkylamines for which CDCl3 could be advantageously replaced by C6D6 or pyridine-d(5) in order to increase the difference between the chemical shifts. The main advantage of the procedure is its simplicity as it does not involve steps such as activation, heating, solvent evaporation and isolation of the product. Its limitations are the limited series of compounds susceptible to be analysed and the small difference between the chemical shifts of the diastereoisomeric imines obtained. (C) 2002 Elsevier Science B.V. All rights reserved.