End game strategies towards the total synthesis of vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A

• Brett D. Schwartz,
• Craig M. Williams and
• Paul V. Bernhardt

Beilstein J. Org. Chem. 2008, 4, No. 34, doi:10.3762/bjoc.4.34

• , 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A are discussed, with focus on construction of the side chain and peripheral functionality associated with this group of natural products is the current focus of this report. Keywords: diterpenes; furanovibsanin A; 3

• -epi-vibsanin E 50, and 2) bis-epi-3-hydroxyvibsanin E 51. Initial studies concentrated on 26, in that tricarbonyl reduction followed by oxidation was envisaged to give aldehyde 52, which could then undergo reaction with ylid 45 in the hope of gaining access to bis-epi-vibsanin E 50. Reduction with

• directed towards bis-epi-3-hydroxyvibsanin E 51. This manoeuvre was further justified by the fact that diketone 40 was readily available via the allylation/Wacker protocol as described in Scheme 6. Considering the knowledge gained in Scheme 8, it was perceived best not to perform tricarbonyl reduction then