A convergent synthesis of the tricyclic architecture of the guanacastepenes featuring a selective ring fragmentation.
[reaction: see text] This Letter describes a concise, diastereoselective synthesis of the tricyclic carbon framework of the guanacastepene family of natural products. An intermolecular Diels-Alder reaction established a remote stereochemical relationship and facilitated a synthesis of allylic acetate 3, which was subsequently joined with vinylstananne 9 via a Stille coupling. An intramolecular [2 + 2] photocycloaddition then afforded complex cyclobutyl ketone 19, which underwent a stereoelectronically controlled fragmentation to the guanacastepene architecture on treatment with samarium diiodide.
Shipe
William D
WD
Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Sorensen
Erik J
EJ
D004224:Diterpenes / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure
D004224:Diterpenes; C409194:guanacastepene