Synthesis of Aristotelia‐type alkaloids. Part VII. Syntheses of (±)‐sorelline, (±)‐serratenone, and (±)‐aristotelin‐19‐one

Abstract

(1 3. XII. 90) The imine obtained by condensing indole-protected 2-(indol-3-yl)acetaldehyde (5) with the terpinylamine derivative (+)-4 was cyclized in 51% yield to the 19-substituted hobartine derivative ( In the course of these investigations, a novel rearrangement was uncovered: a Lewis acid-catalyzed 1,3-migration of an arylsulfonyl group from the indole N-atom into the benzene ring. The discovery that synthetic (+)-aristotelin-19-one ((+)-34) has decidedly different spectroscopic properties than aristolasicone, a metabolite for which the structure has been recently proposed, led to a revision of the structure of the latter.

Syntheses of Aristotelia Alkaloids: Reflections in the Chiral Pool

“…Following this work, in a series of elegant publications, Borschberg also leveraged the aza-Prins cyclization to access a number of other Aristotelia alkaloids either by directly transforming (-)-1 or using prefunctionalized versions of 27. [20][21][22][23][24][25] To circumvent the problems associated with the Ritter-like reactions, we recently applied a similar aza-Prins reaction to the synthesis of 5. In our approach, the conversion of (-)-19 to (-)-27 was accomplished with a nitro-meditated, Lewis acidcatalyzed azidation and subsequent reduction, which deliver (-)-27 with complete stereoretention.…”