Chemoenzymatic Synthesis of (-)-Ribisins A and B from Dibenzo[b,d]furan

cis-Dihydrodiols, derived from monocyclic aromatic compounds, are valuable chiral pool intermediates for the synthesis of cyclic natural products. A drawback of this approach, to the synthesis of polycyclic secondary metabolites, is that additional rings must be annulated. To date, relatively few chiral natural products have been synthesized from polycyclic arene cis-dihydrodiols. Fungal metabolites, (-)-ribisins A and B, have now been obtained by functional group manipulation of a tricyclic arene metabolite, obtained from toluene dioxygenase-catalyzed regioselective and stereoselective cis-dihydroxylations of dibenzo[b,d]furan. The synthetic sequences were marginally shorter than the alternative routes, using monocyclic arene cis-dihydrodiols, and required no carbon-carbon bond-forming reactions.