Synthesis of 2,5-Bis(spirocyclohexane)-Substituted Nitroxides: New Spin Labeling Agents

Abstract The nitroxides with spirocyclic moieties adjacent to N–O group were shown to demonstrate longer spin echo dephasing times between 80 and 295 K than tetramethyl ones. New spin labels for site-directed spin labeling have been prepared from 2,5-bis(spirocyclohexane)-substituted nitroxides of pyrroline series. The labels synthesized contain terminal acetylene and iodoacetamide groups are analogous to those of tetramethyl type but have some advantages in reduction stability and relaxation rates.