Sempervirine etrahydro-1H-benz[g]indolo[2,3-a]quinolizin-6-ium, 1) the
pentacyclic anhydronium indole alkaloid of Gelsemium sempervirens Ait
. f. (Loganiaceae), has been synthesized in three steps from hexahydro
isochroman-3-one (6) and N-2-(3-indolyl)-ethylamine (tryptamine, 7). T
he condensation product, -2-(hydroxymethyl)-trans-hexahydro-phenylacet
amide (8) arising from 6 and 7 on double cyclization with phosphoryl c
hloride yielded the 3,4-dehydroyohimbane derivative 9. Aromatization o
f rings C and D of compound 9 with 2,3-dichloro-5,6-dicyanobenzoquinon
e (DDQ) in glacial acetic acid, followed by basification, generated se
mpervirine (1).