Synthetic routes to benzyl-functionalized cycloSal-d4T monophosphates (7CH(
2)X-cycloSal-d4TMP) have been developed. Their hydrolytic behavior in basic
aqueous solution (pH = 7.3) was studied and their hydrolysis half-lives we
re determined. It turned out that two different degradation pathways are le
ading to different products: beside the formation of the expected d4TMP and
a styrene type derivative, a phenyl-d4T-phosphodiester was obtained as wel
l. The product distribution was specified.