Synthesis, gene silencing activity, thermal stability, and serum stability of siRNA containing four (S)-5′-C-aminopropyl-2′-O-methylnucleosides (A, adenosine; U, uridine; G, guanosine; and C, cytidine)

( S )-5′- C -Aminopropyl-2′- O -methylnucleosides would be useful for improving the serum stability of therapeutic siRNA molecules without affecting their RNAi activities.