Patent ID: 8809590

Claim:
A method for preparing a compound of formula (I), comprising: reacting a compound of formula (II) with a compound of formula (III) under an alkaline condition and in the presence of a sulfite, wherein, (*) represents a chiral center; the compound of formula (I) and the compound of formula (II) is an R or S configuration or a racemic mixture; R 1 is a straight or branched alkyl containing 1-4 carbon atoms; R 2 is hydrogen, a straight or branched alkyl containing 1-4 carbon atoms; R 3 is a straight or branched alkyl containing 1-6 carbon atoms, alkoxy, cycloalkoxy, an phenyl or substituted phenyl or a heterocyclyl; and R 4 is alkyl, haloalkyl, aryl or substituted aryl wherein the sulfite is an alkaline metal sulfite, an alkaline earth metal sulfite, ammonium sulfite, or zinc sulfite wherein the substituted phenyl or the substituted aryl is substituted with a substituent selected from the group consisting of oxo, halogen, hydroxy, cyano, nitro, amino, alkylamino, dialkylamino, alkyl, alkoxy, haloalkyl, unsubstituted aryl, heterocyclyl, —NR a R b , —NR a C(═O)R b , —NR a C(═O)NR a R b , —NR a C(═O)OR b , —NR a S(═O) 2 R b , —OR a , —C(═O)R a —C(═O)OR a , —C(═O)NR a R b , —OCH 2 C(═O)NR a R b , —OC(═O)NR a R b , —SH, —SR a , —SOR a , —S(═O) 2 NR a R b , —S(═O) 2 R a , —SR a C(═O)NR a R b , —OS(═O) 2 R a and —S(═O) 2 OR a , wherein R a and R b are independently hydrogen, alkyl, haloalkyl, alkoxy, or unsubstituted aryl.