Bis[1-[2(S)-(3,4,5-Trimethoxypheny)butyryl]piperidine-2(S)-carboxylic acid] ester with 1,2-ethanediylbis[imino(2-oxo-2,1-ethanediyl)oxy-3,1-phenylene[(1R)-3-(3,4-dimethoxyphenyl)propylidene]] ester