Optimised synthesis and photochemistry of antenna-sensitised 1-acyl-7-nitroindolines

Benzophenone antenna-sensitised 1-acyl-7-nitroindolines show a significantly enhanced extent of photochemical cleavage in aqueous solution over their non-sensitised analogues and release the carboxylate derived from their 1-acyl group. The present work investigates length and functional group effects in the linker between the benzophenone sensitiser and the nitroindoline and concurrently establishes a more efficient synthetic route to an effective conjugate than previously described. An incidental finding is that a TBDMS ether is stable during claycop-mediated nitration.