Stereoselective synthesis of methyl 3α-ethyl-1,2,3,4,6,7,12,12bβ-octahydroindolo[2,3-a]quinolizine-1α-carboxylate: A key intermediate for the preparation of tacamine-type indole alkaloids

Methyl 3α-1,2,3,4,6,7,12,12bβ-cotahydroindolo[2,3- a ]quinolizine-1α-carboxylate ( 6 ), a key intermediate for the synthesis of tacamine-type indole alkaloids, was prepared in six simple steps from methyl 5-(1′-hydroxyethyl)nicotinate ( 7 ). The last step was the catalytic hydrogenation of the two ethylidene isomers 14 and 15 , both of which gave the target ester stereoselectively.