The synthesis of emetine and related compounds. Part VIII. The synthesis of tubulosine and isotubulosine

Abstract

The constitution (Ic) assigned to tubulosine {3-ethyl-1,3,4,6,7,11b-hexahydro-9,10-dimethoxy-2-(1,2,3,4-tetrahydro-6-hydroxy-β-carbolin-1-yl)-2H-benzo[a]quinolizine} has been confirmed by total synthesis from the (–)-ester (II)(ethyl 3-ethyl-1,3,4,6,7,11b-hexahydro-9,10-dimethoxy-2H-benzo[a] quinolizine-2-acetate) of known configuration. Isotubulosine (Vc), also produced in the synthesis, has been identified with an alkaloid subsequently isolated from Alangium lamarckii.