3-ethyl-1-[2-(1H-indol-3-yl)ethyl]-2,4-piperidinedione

(3R)-1-(2-(1H-indol-3-yl)ethyl)-3-ethyl-4-hydroxy-3-(3-hydroxypropyl)piperidin-2-one

(R)-3-ethyl-1-[2-(1H-indol-3-yl)ethyl]-2,4-dioxo-3-piperidinepropanoic acid

5-ethyl-1-[2-(1H-indol-3-yl)ethyl]-4-hydroxy-6-oxo-1,2,5,6-tetrahydro-3-pyridinecarboxylic acid ethyl ester

2-({[3-(ethoxycarbonyl)propyl][2-(1H-indol-3-yl)ethyl]amino}carbonyl)butanoic acid ethyl ester