When looking at the molecular structures
(Fig. 1) and the biological activities of the aforementioned
bisindoles that went to market, it is apparent that relatively small
structural changes lead to significantly different oncological and
toxicological profiles. For this reason the bisindole family has been,
and continues to be, an important but difficult field of chemical
research that has given rise to many inventive and elegant synthetic
solutions, and keeps providing new challenges [3–8].