2‐(Tert‐butylsulfonyl)‐ethyl 4‐(2,2,6,6‐tetramethylpiperidine‐1‐oxyl) phosphoromorpholidite, a spin‐labeled phosphitylating reagent

Abstract
The spin labeled phosphitylating reagent 2‐(tert‐butylsulfonyl)‐ethyl 4‐(2,2,6,6‐tetramethylpiperidine‐1‐oxyl) phosphoromorpholidite (3) rapidly reacts, in the presence of 1‐hydroxybenzotriazole (HOBt), with primary and even secondary hydroxyl functions to give, after oxidation with iodine, a spin labeled phosphotriester, which can be easily deprotected by base to the pertinent spin labeled phosphodiester.