Substitution reactions between a phosphoroselenoyl chloride and Grignard reagents proceeded smoothly at the phosphorus atom to furnish phosphonoselenoic acid esters. The resulting mixture of diastereoisomers could be readily distinguished on the basis of 31P NMR, and separated by recrystallization or column chromatography to afford diastereoisomerically enriched products. For one of these diastereoisomers, the absolute configuration was determined by carrying out a single-crystal X-ray diffraction analysis.
