Patent ID: 8324373

Claim:
A process for preparing beta-anomer enriched gemcitabine, comprising: carrying out the following reaction: wherein, the substitutions of G1 and G2 are independently the radicals defined by the following structure: wherein, R1 is selected from the group consisting of C1-C3 alkyl and null; R2 is selected from the group consisting of hydrogen, C1-C4 alkyl, phenyl and substituted phenyl; and with the provision that for at least one of G1 and G2, R2 is phenyl or substituted phenyl; the said substituted phenyl is the one substituted by C1-C4 alkyl, or halogen; G3 is selected from the group consisting of alkylsulfonyl, arylsulfonyl, substituted alkylsulfonyl and substituted arylsulfonyl; G4 and G5 are independently selected from the group consisting of C1-C7 trialkylsilyl, t-butoxycarbonyl, carbobenzoxyl, 9-fluoroenylmethylcarbonyl (Fmoc), formyl, acetyl, propionyl, isopropionyl, butyryl, isobutyryl, and pivaloyl; wherein carrying out the reaction includes: preparing a first solution of a compound of formula 12 in an organic solvent selected from the group consisting of 1,2-dichloroethane, toluene, xylene, substituted benzene, anisole, diphenyl ether, substituted diphenyl ether, and a mixture thereof; heating the first solution to a temperature of about 100-150° C.; preparing a second solution of a compound of formula 11 in the organic solvent, where the molar ratio of the compound of formula 12 to the compound of formula 11 is about 2.5 to 15; adding the first solution dropwise to the second solution over a period of about 3 to 7 hours; and heating the resultant reaction solution at reflux for about 3-6 hours.