31P NMR ENANTIOMERIC EXCESS DETERMINATION OF 1-HYDROXYALKYLPHOSPHONIC ACIDS VIA THEIR DIASTEREOISOMERIC PHOSPHONODIDEPSIPEPTIDES

N-protected L-aminoacids are convenient derivatizing reagents for enantiomeric excess determination of chiral 1-hydroxyalkylphosphonic acids by the 31P NMR spectroscopy. 1-Hydroxyalkylphosphonic acid esters coupled with N-protected L-aminoacids by means of the DCC method give the diastereoisomers which are quantitatively distinguishable in the 31P NMR spectra. The values of 31P NMR nonequivalence (0.06–0.60 ppm) differ with the change of the L-aminoacids and the protecting groups. The easily available Boc-L-Val and Boc-L-Phe in optically pure form seem to be promising chiral derivatizing agents. The measured enantiomeric excess of preweighed, enantiomerically enriched samples are in excellent agreement with the expected values.