A Facile Synthesis of Dragmacidin B and 2,5-Bis(6‘-bromo-3‘-indolyl)piperazine

A short synthesis of dragmacidin B (1), 2,5-bis(6'-bromo-3'-indolyl)piperazine (2), and corresponding didebromo analogues 8 and 9 is described. The key steps involve the dimerization of oxotryptamines 4 and 11 to give bis(indolyl)pyrazines 5 and 12, which upon selective reduction and reductive methylation with sodium cyanoborohydride afforded the requisite piperazine natural products.