Synthesis and electrochemical properties of the naturally occurring free radical scavenger carazostatin

A short synthesis of the naturally occurring free radical scavenger carazostatin 1 starting from indol-3-ylacetic acid is described, the key step being the regiospecific Diels–Alder reaction of the indolopyrone 2 with ethyl trimethylsilylpropynoate. Electrochemical studies on carazostatin and some of its derivatives show it to be more easily oxidised than butylated hydroxytoluene (BHT).