Cyclotryptophan Mycotoxins: Short Synthesis of the Desymmetrized meso-Chimonantine Core of Leptosin C

The desymmetrized meso -chimonantine core of leptosin C was prepared in a short stereoselective convergent sequence in 5 steps as the longest linear path from methyl l -tryptophan hydrochloride as starting material. The key step of this approach was a diastereoselective [4+2] cycloaddition between the bromooxindole and tryptophan derivatives allowing to define the adjacent quaternary benzylic centers in a high chemical yield.