(6S,12bR)-3-(benzyloxycarbonyl)-12-(tert-butoxycarbonyl)-6-[(tert-butoxycarbonyloxy)-methyl]-4-oxo-1,4,6,7,12,12b-hexahydroindolo[2,3-a]quinolizine

(6S,12bR)-12-(tert-butoxycarbonyl)-6-[(tert-butoxycarbonyloxy)methyl]-4-oxo-3,3-bis(phenylthio)-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine

(6S,12bR)-12-(tert-butoxycarbonyl)-6-[(tert-butoxycarbonyloxy)methyl]-4-oxo-3-(phenylthio)-1,4,6,7,12,12b-hexahydroindolo[2,3-a]quinolizine

13-(tert-butyl) 1-methyl (4R,4aR,7S,13bR,14aR)-7-(((tert-butoxycarbonyl)oxy)methyl)-4-methyl-2,5-dioxo-4a-(phenylsulfonyl)-1,3,4,4a,5,7,8,13b,14,14a-decahydroindolo[2',3':3,4]pyrido[1,2-b]isoquinoline-1,13(2H)-dicarboxylate

(6S,12bR)-12-(tert-butoxycarbonyl)-6-[(tert-butoxycarbonyloxy)methyl]-4-oxo-3-(phenylsulfonyl)-1,4,6,7,12,12b-hexahydroindolo[2,3-a]quinolizine