(2'S,3'S,4'R)-5'-O-benzoyl-3'-deoxy-3' beta-diethylphosphono-2'-O-tert-butyldimethylsilyluridine

3'-Hydroxy-3'-diethylphosphononucleosides readily undergo radical deoxygenation under modified Barton conditions to give two diastereomers of the parent diethyl phosphonate. However, the stereochemistry of the diastereomers is difficult to establish by spectral means. When the major product of one such reaction was obtained in crystalline form, a single crystal diffraction analysis was conducted on that diastereomer, the title compound, C26H39N2O9PSi.