A method for the preparation of a compound of formula or a tautomer, a pharmaceutically acceptable salt, a hydrate, or solvate thereof, wherein B is selected from the group comprising purinyl, pyrimidyl, or aza or deaza analog thereof, or -NR 1 R 2; each group being optionally substituted by one or more substituents independently selected from halo, amino, hydroxyl, C 1-6 alkyl, aminoC 1-6 alkyl, nitro, formamido, -NHR 18 or OR 7; and wherein a carbon atom of said purinyl or pyrimidyl can be oxidized to form a C=O, wherein R 7 is selected from C 1-4 alkyl, C 6-10 arylC 1-6 alkylene or C 6-10 aryl, R 18 is selected from C 6-10 arylC 1-6 alkylene, C 1-6 alkylcarbonyl, haloC 1-6 alkylcarbonyl, C 1-6 alkyloxycarbonyl, 9-fluorenylmethyloxycarbonyl, or C 6-10 arylC 1-6 alkyloxycarbonyl; and R 1 is selected from hydrogen, C 6-10 aryl, C 6-10 arylC 1-6 alkylene, C 1-4 alkyl, C 6-10 haloaryl, C 1-4 haloalkyl or C 6-10 haloarylC 1-6 alkylene; R 2 is selected from C 6-10 aryl, C 6-10 arylC 1-6 alkylene, C 1-4 alkyl, C 6-10 haloaryl, C 1-4 haloalkyl or C 6-10 haloarylC 1-6 alkylene; comprising the step of coupling a compound of formula, with a compound of formula B'-H under Mitsunobu conditions, wherein H is hydrogen, wherein B' is B or selected from the group consisting of purinyl, pyrimidyl, or aza or deaza analog thereof; each group being substituted by one or more substituents independently selected from -NR 24 R 25; and wherein a carbon atom of said purinyl or pyrimidyl can be oxidized to form a C=O, wherein R 24 and R 25 are independently hydrogen or C 1-6 alkyl; wherein said compound of formula is a compound of formula wherein n is an integer from 0 to 5, X is selected from C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, halogen, hydroxyl, C 1-6 alkoxy or amino; the method further comprising the step of hydrolyzing or reducing a compound of formula, obtained via the condensation of compounds of formula with compounds of formula B'-H; wherein n is an integer from 0 to 5 and X is C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, halogen, hydroxyl, C 1-6 alkoxy or amino; wherein the compound of formula is a specific enantiomer of formula (A') or (A"): wherein B is selected from the group comprising purinyl, pyrimidyl, or aza or deaza analog thereof, or -NR 1 R 2; each group being optionally substituted by one or more substituents independently selected from halo, amino, hydroxyl, C 1-6 alkyl, aminoC 1-6 alkyl, nitro, formamido, -NHR 18 or OR 7; and wherein a carbon atom of said purinyl or pyrimidyl can be oxidized to form a C=O, wherein R 7 is selected from C 1-4 alkyl, C 6-10 arylC 1-6 alkylene or C 6-10 aryl, R 18 is selected from C 6-10 arylC 1-6 alkylene, C 1-6 alkylcarbonyl, haloC 1-6 alkylcarbonyl, C 1-6 alkyloxycarbonyl, 9-fluorenylmethyloxycarbonyl, or C 6-10 arylC 1-6 alkyloxycarbonyl; and R 1 is selected from hydrogen, C 6-10 aryl, C 6-10 arylC 1-6 alkylene, C 1-4 alkyl, C 6-10 haloaryl, C 1-4 haloalkyl or C 6-10 haloarylC 1-6 alkylene; R 2 is selected from C 6-10 aryl, C 6-10 arylC 1-6 alkylene, C 1-4 alkyl, C 6-10 haloaryl, C 1-4 haloalkyl or C 6-10 haloarylC 1-6 alkylene; wherein H is hydrogen, wherein B' is B or selected from the group consisting of purinyl, pyrimidyl, or aza or deaza analog thereof; each group being substituted by one or more substituents independently selected from -NR 24 R 25; and wherein a carbon atom of said purinyl or pyrimidyl can be oxidized to form a C=O, wherein R 24 and R 25 are independently hydrogen or C 1-6 alkyl; wherein said compound of formula is a compound of formula wherein n is an integer from 0 to 5, X is selected from C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, halogen, hydroxyl, C 1-6 alkoxy or amino; the method further comprising the step of hydrolyzing or reducing a compound of formula, obtained via the condensation of compounds of formula with compounds of formula B'-H; wherein n is an integer from 0 to 5 and X is C 1-6 alkyl, C 1-6 haloalkyl, C 2-6 alkenyl, C 2-6 alkynyl, halogen, hydroxyl, C 1-6 alkoxy or amino; wherein the compound of formula is a specific enantiomer of formula (A') or (A"):