Provided is a method for biocatalytic synthesis of Sitagliptin and intermediates thereof, in particular, provided are compounds of Formula (I) and Formula (II), or pharmaceutically acceptable salts thereof, a polypeptide capable of catalyzing conversion of a compound of Formula (I) to a compound of Formula (II), a nucleic acid encoding the polypeptide, a vector and a cell comprising the nucleic acid. In addition, also provided are a method for producing a compound of Formula (II) and Sitagliptin by using the polypeptide and the compound of Formula (I), and a method for preparing the polypeptide.