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