Pigments of Fungi. XXXIV. Synthesis of Austrocorticinic Acid, (±)-Austrocorticin and the Methyl Ester of Austrocorticone

Austrocorticinic acid (1) is synthesised via the isophthalic acid (8) which is available in 37% yield over three steps from ethyl (3',5'-dimethoxyphenyl)acetate (12). Intramolecular Friedel-Crafts acylation of the acid (8) yields the anthrone (6) which, as the ester (7), is smoothly oxidized to methyl austrocorticinate (14). Hydrolysis of (14) gives (1). Bromination of (15) gives the benzylic bromide (16) that is converted into racemic austrocorticin rac-(2) via the trifluoroacetate (18), and into the methyl ester (21) of austrocorticone (3) by oxidation with dimethyl sulfoxide.