4-Fluorophenyl 3-nitro-2-pyridinesulfenate as a practical protecting agent for amino acids.

We report a new protecting agent (1, Npys-OPh(pF)) for 3-nitro-2-pyridine (Npy) sulfenylation of amino, hydroxy, and thiol functional groups. Several Npys phenoxides were synthesized from Npys chloride (Npys-Cl) and phenols in the presence of base in 1-step reaction, and their ability for Npy-sulfenylation was evaluated. As a result, 1 was selected as a new Npy-sulfenylation agent with advantages including improved physicochemical stability, more controllable reactivity, and easier handling than the conventional protecting agent Npys-Cl.