Access to phenolic fungal metabolites via the acid-catalysed Claisen rearrangement. The total synthesis of (±)-mellein, aurocitrin, and 5′,6′-dihydroaurocitrin
Abstract
Regioselective trifluoroacetic acid catalysed rearrangement of allyl 5-allyloxy-2-hydroxybenzoate (2b) with concomitant cyclisation of the initial product permits the simple preparation of 3,4-dihydro-5,8-dihydroxy-3-methylisocoumarin (5). Hydrogenolysis of the non-hydrogen bonded hydroxy group yields (±)-mellein (7) whereas elaboration of the lactone moiety of compound (5) provides access to aurocitrin (8b) and its side chain analogues.