Disclosed herein are nucleoside phosphoramidates of formula 4 and their use as agents for treating viral diseases. These compounds are inhibitors of RNA-dependent 5 RNA viral replication and are useful as inhibitors of HCV NS5B polymerase, as inhibitors of HCV replication and for treatment of hepatitis C infection in mammals. Disclosed is also a process for preparing compound represented by formula 4: (Formula 4) wherein P* represents a chiral phosphorus atom, which comprises: a) reacting an isopropyl-alanate, (Formula A), a di-X'-phenylphosphate, (Formula B), 2'-deoxy-2f-fluoro-2'-C-methyluridine, (Formula 3), and a base to obtain a first mixture comprising 4； wherein X is a conjugate base of an acid, n is 0 or 1, and X' is a halogen, b) reacting the first mixture with a protecting compound to obtain a second mixture comprising 4； and c) optionally subjecting the second mixture to crystallization, chromatography or extraction in order to obtain 4.
