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-1 wherein the Active is a nucleoside, a nucleoside-analog, or a non-nucleoside; wherein the nucleoside is selected from wherein the nucleoside-analog is selected from wherein the non-nucleoside is selected from wherein W is an aryl or -(CH 2) n SC C(CH 3)n,(CH 2 OH) 3-m; wherein n is 2 or 3 and m is 0, 1,2, or 3; wherein LG is selected from the group consisting of 2-nitrophenoxide, 4-nitrophenoxide, 2,4-dinitrophenoxide, pentafluorophenoxide, 2-chloro-4-nitrophenoxide and 2,4-dichlorophenoxide; wherein R is a C 1-6 alkyl; and wherein R' is a C 1-6 alkyl or a C 3-7 cycloalkyl; and (b) optionally deprotecting the compound obtained in step (a) to obtain the enantiomerically- or diastereomerically-enriched phosphorous-containing active, salt, or phamnaceutically acceptable salt thereof of formula I-1, wherein the enatiomerically- or diastereomerically-enriched compound of formula II-1 is obtained by crystallization from a composition comprising: i. a first composition; ii. a leaving group precursor; iii. a non-nucleophilic base; and iv. a liquid composition comprising at least one of a solvent and an anti-solvent; wherein the first composition comprises Rp- II-1 and Sp- II-1: and wherein the leaving group precursor is 2,4-dinitrophenol, 4-nitrophenol, 2-nitrophenol, 2-chloro-4-nitrophenol, 2,4-dichlorophenol, or pentafluorophenol. (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-1 wherein the Active is a nucleoside, a nucleoside-analog, or a non-nucleoside; wherein the nucleoside is selected from wherein the nucleoside-analog is selected from wherein the non-nucleoside is selected from wherein W is an aryl or -(CH 2) n SC C(CH 3)n,(CH 2 OH) 3-m; wherein n is 2 or 3 and m is 0, 1,2, or 3; wherein LG is selected from the group consisting of 2-nitrophenoxide, 4-nitrophenoxide, 2,4-dinitrophenoxide, pentafluorophenoxide, 2-chloro-4-nitrophenoxide and 2,4-dichlorophenoxide; wherein R is a C 1-6 alkyl; and wherein R' is a C 1-6 alkyl or a C 3-7 cycloalkyl; and wherein W is an aryl or -(CH 2) n SC C(CH 3)n,(CH 2 OH) 3-m; wherein n is 2 or 3 and m is 0, 1,2, or 3; wherein LG is selected from the group consisting of 2-nitrophenoxide, 4-nitrophenoxide, 2,4-dinitrophenoxide, pentafluorophenoxide, 2-chloro-4-nitrophenoxide and 2,4-dichlorophenoxide; wherein R is a C 1-6 alkyl; and wherein R' is a C 1-6 alkyl or a C 3-7 cycloalkyl; and (b) optionally deprotecting the compound obtained in step (a) to obtain the enantiomerically- or diastereomerically-enriched phosphorous-containing active, salt, or phamnaceutically acceptable salt thereof of formula I-1, wherein the enatiomerically- or diastereomerically-enriched compound of formula II-1 is obtained by crystallization from a composition comprising: i. a first composition; ii. a leaving group precursor; iii. a non-nucleophilic base; and iv. a liquid composition comprising at least one of a solvent and an anti-solvent; wherein the first composition comprises Rp- II-1 and Sp- II-1: and wherein the leaving group precursor is 2,4-dinitrophenol, 4-nitrophenol, 2-nitrophenol, 2-chloro-4-nitrophenol, 2,4-dichlorophenol, or pentafluorophenol. i. a first composition; ii. a leaving group precursor; iii. a non-nucleophilic base; and iv. a liquid composition comprising at least one of a solvent and an anti-solvent;