tert-butyl (4S)-4-ethyl-4,6-dihydroxy-3,10-dioxo-1,8-dihydropyrano[3,4-f]indolizine-7-carboxylate

(4'S)-4'-ethyl-1',4',7',8'-tetrahydro-4'-hydroxy-3'H,10'H-spiro[1,3-dioxolane-2,6'-pyrano[3,4-f]indolizine]-3',10'-dione

(S)-4'-ethyl-4'-(methoxymethoxy)-7',8'-dihydrospiro[[1,3]dioxolane-2,6'-pyrano[3,4-f]indolizine]-3',10'(1'H,4'H)-dione

(S)-α-ethyl-α-hydroxy-1,1-(ethylenedioxy)-6-hydroxymethyl-5-oxo-1,2,3,5-tetrahydroindolizine-7-[N-(1S)-1-phenylethyl]acetamide

4'-ethyl-1',4',7',8'-tetrahydro-4'-hydroxy-3'H,10'H-spiro[1,3-dioxolane-2,6'-pyrano[3,4-f]indolizine]-3',10'-dione