Concise total synthesis of phidianidine A and B

The shortest total synthesis of cytotoxic indole alkaloids phidianidine A and B is described. Rapid assembly of the 1,2,4-oxadiazole core from a novel N-hydroxyguanidine and the corresponding indole-3-acetic acid chloride led to formal syntheses of phidianidine A and B in only three steps from known compounds. Deprotection under standard conditions provided the trifluoroacetate salts of phidianidine A and B in quantitative yield.