Method for transforming isomer

The invention relates to a method for recycling an isomer such as sitagliptin and belongs to the technical field of pharmacy. The isomer and mercaptan are transformed into a racemate under the action of a free radical initiator, and then a compound needing configuration can be obtained through a common splitting method. By adopting the method, the isomer regarded as waste can be reutilized, the production cost is reduced, and the industrial production is facilitated.