rel-(2R,3S,4S)-3-ethyl-4-hydroxy-2-piperidinecarboxylic acid

4-Chloro-3-ethyl-piperidine-1-carboxylic acid methyl ester

rel-(2R,3R,4R)-4-acetylamino-3-ethyl-1,2-piperidinedicarboxylic acid dimethyl ester