Abstract: The present invention provides processes for preparing intermediates useful in the preparation of gemcitabine and other nucleosides, and processes for preparing gemcitabine therewith. Exemplary intermediates include mixtures of D-erythro and D-threo isomers of 3-(hydroxy)-2,2-difluoro-3-(2,2-dimethyldioxolan-4-yl)-propionic acid salts. Also provided is a process for selectively isolating the D-erythro and D-threo isomers of D-erythro and D-threo isomers of 3-(hydroxy)-2,2-difluoro-3-(2,2-dimethyldioxolan-4-yl)-propionic acid salts, and processes for using such isomers in the preparation of nucleoside analogs such as, e.g., gemcitabine, intermediates thereof, and analogs thereof.

Abstract: The present invention provides novel intermediates, which preferably include 3-substituted, alkyl 2,2-difluoro-3-hydroxy-3-(2,2-dialkyldioxolan-4-yl)-propionate derivatives, and 3,5-disubstituted-2-deoxy-2,2-difluoro-1-oxo-D-ribose derivatives. The present invention also provides processes for producing such intermediates and processes for producing gemcitabine therewith.

Abstract: The present invention provides processes for preparing novel chemical substances that are useful as intermediates in the preparation of gemcitabine and processes for preparing gemcitabine therewith. Exemplary intermediates include mixtures of D-erythro and D-threo (3R- and 3S-) isomers of 3-(hydroxy)-2,2-difluoro-3-(2,2-dimethyldioxolan-4-yl)propionic acid salts. Also provided is a novel process for selectively isolating the D-erythro and D-threo isomers of the said salts in purities of at least about 95%, and processes of using them for preparing nucleoside analogs such as, e.g., gemcitabine and intermediates and analogs thereof.