| 1-boc-4-oxo-3-piperidinecarboxylic acid ethyl ester |
| 1-tert-butoxycarbonyl-3-ethoxycarbonyl-4-piperidone |
| 1-boc-3-ethoxycarbonyl-4-piperidone |
| ethyl 1-tert-butoxycarbonyl-4-oxo-3-piperidinecarboxylate |
| 1-tert-butoxycarbonyl-4-oxo-3-piperidinecarboxylic acid ethyl ester |
| ethyl 1-boc-4-oxo-3-piperidinecarboxylate |