DETERMINATION OF ABSOLUTE-CONFIGURATION OF ALPHA-HYDROXYPHOSPHONATES BY P-31 NMR-SPECTROSCOPY OF CORRESPONDING MOSHER ESTERS

(R)-MTPA esters of alpha-hydroxyphosphonates 1a-h of known absolute configuration were prepared and their P-31 NMR spectra were recorded. The chemical shifts of the P-31 signals of the derivatized (S)-alcohols are consistently downfield relative to the signals of the corresponding (R)-alcohols. A variety of racemic and diastereomeric alpha-hydroxyphosphonates 1i-o and their (R)-MTPA esters were prepared. The P-31 chemical shift differences are large enough to securely assign absolute configurations to alpha-hydroxyphosphonates.