Abstract Two phytoalexins, previously isolated from carnation infected by Phytophthora parasitica D., were synthesized: 2-phenyl-7-hydroxy-4H-3, l-benzoxazin-4-one (Dianthalexin) and 2-(2-hydroxybenzoyl)-amino-4-methoxybenzoic acid (Dianthramide A). The first one was obtained by using potassium t-butoxide in dimethylformamide to prevent its heterocycle opening. Five novel other analogous compounds were also prepared.