Synthesis, Derivatization and Photochemical Control of an ortho‐Functionalized Tetrafluorinated Azobenzene‐Modified siRNA

We report the synthesis of an ortho‐functionalized tetrafluorinated azobenzene phosphoramidite for its site‐specific incorporation into RNA. The tetrafluorinated azobenzene is embedded within the antisense strand of an siRNA duplex to form an ortho‐functionalized tetrafluorinated azobenzene‐containing siRNA (F‐siRNAzo). The F‐siRNAzo is inactivated via trans to cis conversion with green light (530 nm), and reactivated with blue light (470 nm) via cis to trans conversion in cell culture. The long half‐life and stability of the tetrafluorinated azobenzene unit allows for reversible control of the F‐siRNAzo in cell culture for up 72 hours. RNAi activity is controlled by a modified tetrafluorinated azobenzene derivative embedded within a short interfering RNA. In mammalian cells, we can inactive the siRNA duplex for green light for up to 72 hours, and no RNA interference activity occurs. When the blue light is administered, the complex isomerizes back to an active form, and RNA interference activity resumes.