Total synthesis of lycogarubin C utilizing the Kornfeld-Boger ring contraction

摘要

An efficient synthesis of lycogarubin C (3) was completed in seven steps from the known 1-(phenylsul-fonyl)indole-3-carbaldehyde in 30% overall yield, via a Diels-Alder reaction between (Z)-1,2-di(1H-indol-3-yl)ethene 9b and dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate (7), followed by a Kornfeld-Boger ring contraction to form the pyrrole ring.