4-substituted pyrrolidine formyl thiomorpholine DPP-IV (Dipeptidyl Peptidase IV) inhibitor

The invention discloses a 4-substituted pyrrolidine formyl thiomorpholine DPP-IV (Dipeptidyl Peptidase IV) inhibitor and a preparation method therefor and use thereof. Specifically, the invention relates to a compound represented by a formula (I) shown in the description, a stereoisomer thereof and pharmaceutically-acceptable salts thereof, wherein R1 and R2 are as defined in the description. The invention also relates to a pharmaceutical composition containing the compound disclosed by the invention, use of the compound disclosed by the invention in preparation of drugs for methods for treating and/or preventing too-high DPP-IV activity or DPP-IV overexpression related diseases or disease symptoms, and a method for treating related diseases by using the compound disclosed by the invention. The compound disclosed by the invention has effective DPP-IV inhibiting activity.