Total syntheses of the slime mold alkaloid arcyriacyanin A

Arcyriacyanin A (1) has been synthesized by three different routes. In the first synthesis the bisbromomagnesium salt of 2,4'-biindole (5) was treated with dibromomaleimide (6) to yield arcyriacyanin A (1). The second approach used an intramolecular Heck reaction for the cyclization of a 4-(triflyloxy)arcyriarubin 8 to N-methylarcyriacyanin A (2), Thirdly, compound 2 was obtained by a domino Heck reaction between 3-bromo-4-[1-(tert-butoxycarbonyl)indol-3-yl]-1-methylmaleimide (9) and 4-bromoindole (10). The N-methyl derivative 2 could be transformed into arcyriacyanin A (1) by standard methods.