Stereospecific synthesis of the (3aα,11α,12aα)-decahydrobenzo[a]pyrrolo[3,2-g]quinolizine ring system

A stereospecific synthesis of racemic (3aα,11bα,12aβ)-1,2,3,3a,4,6,7,11b,12,12a-decahydro-9-methoxy-1-(methylsulfonyl)benzoα]pyrrolo3,2-g]quinolizine (2) is reported. Cyclocondensation of lithiated pyrrolecarboxamide 5 and dihydroisoquinoline 6 afforded the key tetracyclic intermediate 7 . Hydrogenation of 7 gave the 3aα,11bα,12aα-isomer 9 which was subsequently converted to 2 .