Derivatives of 1-hydroxy-2, 2, 6, 6-tetramethylpiperidine were oxidized by potassium nitrosodisulfonate (FREMY's salt) to 2, 2, 6, 6-tetramethylpiperidine-1-oxyls. A triphenylphosphine-alkylene reaction, a Grignard reaction, and esterification resulted in derivatives with aldehyde groups.
![6-hydroxy-5,5,7,7-tetramethyl-1-oxa-6-azaspiro[2.5]octane Structure](https://image.chemsrc.com/caspic/073/53086-01-4.png)
