13a-ethyl-2,3,5,6,13,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridin-12(4¹H)-imine

3-(3-ethyl-2-methoxy-3-tetrahydrofuryl)propionic acid

(3S)-3-ethyl-5-hydroxy-3-(3-hydroxypropyl)dihydrofuran-2(3H)-one

3-(3-ethyl-2-oxotetrahydrofuran-3-yl)propanoic acid