Triacetonamine826-36-836 % similar 2,2,6,6-Tetramethyl-4-piperidone hydrochloride33973-59-032 % similar 2,2,6,6-Tetramethylpiperidine768-66-131 % similar 5,5-Dimethylpiperidine-2,4-dione118263-81-330 % similar