| Abstract
| - The pentacyclic alkaloids vincadifformine(9), ψ-vincadifformine (15), andepi-ψ-vincadifformine(16) could be synthesized by intramolecularfree-radical-induced cyclizations of the tetracyclicintermediates 7, 8, and 18, which wererespectively obtained by condensation of the indoloazepine1 with 2-(phenylselenyl)butyraldehyde and subsequentNb-alkylation of the resultingtetracyclicamines 2 and 3, or from condensation of(phenylselenyl)acetaldehyde with the alkylated indoloazepine 17. The intermediates 2 and3 also gave 3-oxovincadifformine (21) by anintermolecularradical alkylation with methyl acrylate. Their alkylation with(Z)-1,3-diiodopropene, phenylselenoxide elimination, and intramolecular Heck reactions providedtabersonine (24) and 18,19-didehydrotabersonine (27).
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