Divergent Synthesis of Bioactive Resorcinols Isolated from the Fruiting Bodies of Hericium erinaceum: Total Syntheses of Hericenones A, B, and I, Hericenols B–D, and Erinacerins A and B

Total syntheses of 5'- and 7'-oxidized geranyl resorcylates isolated from the fruiting bodies of Hericium erinaceum and the submerged cultures of a Stereum species were achieved. Our synthesis features derivatization of a suitably functionalized 5'-oxidized geranyl phthalide as a common intermediate, which was obtained by Stille coupling between the phthalide core and the side chain, into a series of natural products by divergent functional group manipulations. The crucial C5'-oxygen functionality was installed at the initial stage by alkylation by an α-cyano ethoxyethyl ether. From a common synthetic intermediate, eight total syntheses including hericenones A, B, and I, hericenols B-D, and erinacerins A and B were achieved (hericenol B and erinacerin B were synthesized as racemates). The structure of hericenone B established in the isolation paper was unambiguously revised as the carbonyl regioisomer at the lactam moiety.