Disclosed herein is a process for preparing an enantiomerically- or a diastereomerically enriched phosphorus-containing active, salt, or pharmaceutically acceptable salt thereof, of formula I-1, which comprises the steps of: (a) reacting a protected or unprotected Active with a base to form a salt of said active and then reacting said salt with an enantiomerically- or a diastereomerically enriched compound of formula II-1wherein the Active is a nucleoside, a nucleoside-analog, or a non-nucleoside.
