Total Synthesis of (+)-Elacomine and (−)-Isoelacomine,Two Hitherto Unnamed Oxindole Alkaloids from Elaeagnus commutata

Racemic elacomine ((±)- 2 ), a hemiterpene spiro oxindole alkaloid from Elaeagnus commutata, was synthesized in five steps from 6-methoxytryptamine ( 19 ) in 16% overall yield (Scheme 3). The final oxidative rearrangement of the corresponding β-carboline precursor (±)- 21 furnished isoelacomine ((±)- 22 ) as a by-product (6% overall yield). A more elaborate route that started from L -tryptophan furnished (+)- 2 and (?)- 22 with optical purities of 76% (Scheme 4) and established the absolute configuration of these compounds. A reinvestigation of the alkaloidal content of the roots of E. commutata showed that both elacomine and isoelacomine occur naturally in racemic form.