(4R,5R)-(+)-5-ethyl-1-(4-hydroxy-3-methoxyphenethyl)-2-oxo-4-piperidineacetic acid ethyl ester

(2R,3R)-10-benzyloxy-2-ethoxycarbonylmethyl-3-ethyl-1,2,3,4,6,7-hexahydro-9-methoxybenzoquinolizinium chloride

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

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

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