4-Piperidineacetic acid,1-[2-[3,4-dimethoxy-2-(phenylmethoxy)phenyl]-2-hydroxyethyl]-3-ethyl-,ethyl ester, [1(R*),3a,4b]-(±)-

(3R,4S)-(+)-1-(3,4-dimethoxyphenacyl)-3-ethyl-4-piperidineacetic acid ethyl ester

4-Piperidineacetic acid,1-[2-(3,4-dimethoxyphenyl)-2-hydroxyethyl]-3-ethyl-2-oxo-, ethyl ester,[3R-[1(S*),3a,4a]]-

{(3R,4S)-1-[2-(3,4-Dimethoxy-phenyl)-2-hydroxy-ethyl]-3-ethyl-piperidin-4-yl}-acetic acid ethyl ester; compound with carbonic acid