The present invention relates to more improved process for preparing
2'-deoxy-2',2'-difluoronucleoside and its intermediate. The present
invention provide a process for preparing an erythro enantiomer in
greater than 98% purity, comprising forming a lactone ring by hydrolyzing
ethyl (3RS)-2,2-difluoro-3-hydroxy-3-(2,2-dimethyloxolan-4-yl)propionate
is hydrolyzed in the presence of hydrolysis reagents selected from acetic
acid or chloroacetic acid, water and a mixture of organic solvents
selected from the group comprising acetonilrile, dioxane, tetrahydrofuran
or toluene, introducing a substituted benzoyl protecting group at the
3-position and 5-position, and recrys- tallizing said erythro enantiomer.
Further, the present invention provides a process for selectively
preparing, in greater than 99% purity, a beta-anomer
2'-deoxy-2',2'-difluoronucleoside at the 3'-position and 5'-position that
are protected by a substituted benzoyl in a 2:3 alpha/beta anomeric
ratio.