| Sitagliptin Impurity 8 | NA | Ax-IMP2219 |
| siloxane Impurity | 556-71-8 | Ax-IMP1509 |
| Sitagliptin Impurity 7 | NA | Ax-IMP2218 |
| Tetracosene Process Impurity 1 | 4371-74-8 | Ax-IMP1507 |
| Sitagliptin Impurity 5 | NA | Ax-IMP2217 |
| Tetracosene Process Impurity 2 | 858474-12-1 | Ax-IMP1508 |
| SKY-IV; Sitagliptin Impurity 4 | NA | Ax-IMP2216 |
| Tetracos-1-ene | 10192-32-2 | Ax-IMP1506 |
| Sitagliptin Impurity 3 | NA | Ax-IMP2213 |
| Sitagliptin Process Impurity 2 | 769195-20-2 | Ax-IMP2212 |