SYNTHESIS, CONFIGURATION, AND CHEMICAL-SHIFT CORRELATIONS OF CHIRAL 1,3,2-OXAZAPHOSPHOLIDIN-2-ONES DERIVED FROM L-SERINE

The reaction between (S)-methyl N-benzylserinoate and phosphorous oxychloride leads to the diastereomeric chloro-l,3,2-oxazaphospholidin-2-ones. Reaction of the chloridates with alcohols or phenols in the presence of base affords the corresponding alkoxy (or aryloxy) derivatives (66-94%), which were readily separated by standard chromatographic methods. The stereochemical arrangement of these compounds was established by NMR chemical shift correlations (carbon-13 and phosphorus-31) and single-crystal X-ray analysis. The trans geometry of the carbomethoxy and exocyclic phosphorus ligand resulted in approximately a 1 ppm upfield shift in the phosphorus-31 spectra relative to the cis isomer. The carbon-13 NMR spectra revealed an opposite trend in the heteroatom-bound alkyl region with most of the trans isomer signals appearing downfield (0.2-1.2 ppm) from the corresponding cis isomer. © 1990, American Chemical Society. All rights reserved.