4-Carboxy-N-nitrosopiperidine 4-Piperidinecarboxylic acid, 1-nitroso- 5-22-01-00252 (Beilstein Handbook Reference) 6238-69-3 BRN 0137256 Isonipecotic acid, 1-nitroso- N-Nitrosoisonipecotic acid Nitrosoisonipecotic acid