Total synthesis of aigialomycin D using a Ramberg-Bäcklund/RCM strategy.

The bioactive resorcylic acid lactone aigialomycin D (1) has been synthesized by a novel combination of ring-closing metathesis (RCM) and Ramberg-Bäcklund reactions. This synthetic strategy enables the C1'-C2' alkene to be masked as a sulfone during formation of the macrocycle by ring closing metathesis at the C7'-C8' olefin, thus avoiding competing formation of a cyclohexene. A subsequent Ramberg-Bäcklund reaction efficiently produces the C1'-C2' E-alkene. This combined RCM/Ramberg-Bäcklund reaction strategy should be widely applicable to the synthesis of macrocyclic dienes.