Abstract
Three marine β-carboline alkaloids, eudistomin H, I, and P (5, 4, and 6), were synthesized. The Bischler-Napieralski reaction of N-(N-benzyloxycarbonylprolyl)tryptamine (11) gave the 3, 4-dihydro-β-carboline (12), which was converted to eudistomin I (5) via 13 on deprotection and dehydrogenation. Compound 13 was obtained directly from N-(N-tert-butoxycarbonylprolyl)tryptamine (17) by means of the Bischler-Napieralski reaction with polyphosphoric ester-dichloroethane. The bromination of 5 with N-bromosuccinimide (NBS)-acetic acid gave eudistomin H (4). Bromination of the 5-methoxypyrrolo[2, 3-b]indole (21) obtained from the 5-hydroxytryptamine (18) gave the 6-bromo derivative (22) which afforded 6-bromo-5-methoxytryptamine (25) on alkaline hydrolysis. The Bischler-Napieralski reaction of the 6-bromo-5-methoxy-N-prolyltryptamine (27) gave the 1-pyrrolinyl-3, 4-dihydro-β-carboline (29). Dehydrogenation of 29 with NBS followed by demethylation with boron tribromide provided eudistomin P (6) via 30.
