Total Synthesis of (±)-Kelsoene

Abstract

(±)-Kelsoene (1) has been synthesized in 15 steps from commercially available cyclopent-2-en-1-one. Key steps include (a) a methylenecyclopentane annulation of cyclopent-2-en-1-one using the bifunctional cuprate reagent lithium cyano(4-chlorobut-1-en-2-yl)cuprate and (b) a highly stereoselective [2+2]-photocycloaddition of ethylene to the bicyclic enone 10.

Key words

kelsoene - annulation - bifunctional reagent - photocycloaddition - Wilkinson’s catalyst - Lombardo’s reagent

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3

Previous literature reports have used different structural numbering systems for kelsoene. In this paper, we have chosen to number the kelsoene skeleton according to IUPAC protocol for tricyclic ring systems

28

This experiment was carried out using the CDCl₃ solutions that had been employed to record the NMR spectra of compound 14