(3R,4S)-2-ethoxy-3-ethyl-3,4,5,6-tetrahydro-4-pyridineacetic acid ethyl ester

(3R,4S)-6-ethoxy-3-ethyl-2,3,4,5-tetrahydro-4-pyridineacetic acid ethyl ester

(4S,5R)-1-(2-benzyloxy-3,4-dimethoxyphenacyl)-5-ethyl-2-oxo-4-piperidineacetic acid ethyl ester