Synthesis, determination of stereochemistry, and evaluation of new bisindole alkaloids from the myxomycete Arcyria ferruginea: an approach for Wnt signal inhibitor.

To determine the stereochemistry of dihydroarcyriarubin C (1), new bisindole alkaloid isolated from the myxomycete Arcyria ferruginea, cis- (2) and trans-dihydroarcyriarubin C (3) were synthesized. Comparison of their NMR characteristics allowed the trans stereochemistry of the natural product to be confirmed. Moreover, the Wnt signal inhibitory activities of 2 and 3 were compared with that of arcyriaflavin C (4), which is a natural product containing a bond between C-2 and C-2'. The cis-dihydroarcyriarubin C (2) showed moderate inhibition of Wnt signal transcription, which suggests that bisindole frameworks might be useful as small-molecule Wnt signal inhibitors.