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

• -hydroxyvibsanin E; 3-O-methylfuranovibsanin A; natural products; terpenoids; vibsane; vibsanin E; Viburnum; Introduction Vibsane-type diterpenes occur exclusively in Viburnum species such as V. awabuki [1], V. odoratissimum [2] and V. suspensum [3], and can be regarded as quite rare natural products. Nine

• -hydroxyvibsanin E (13), furanovibsanin A (14), and 3-O-methylfuranovibsanin A (15) (Figure 2) building on core structures 10–12 (Figure 2). Results and Discussion As shown in the first generation retrosynthesis (Scheme 1) a [4+2] cycloaddition to install the required functionality was envisaged. All attempts