Synthesis and testing of chromogenic phenoxazinone substrates for β-alanyl aminopeptidase

Novel 7-N-(β-alanyl)aminophenoxazin-3-one salts 27a–d have been synthesized and tested as chromogenic substrates for β-alanyl aminopeptidase, which is present in Pseudomonas aeruginosa, the most common respiratory pathogen in patients with cystic fibrosis. The biological results show that 7-N-(β-alanyl)amino-1-pentylphenoxazin-3-one trifluoroacetate salt27a is a chromogenic substrate for this bacterium, with a low degree of diffusion in nutrient media for growing bacterial cultures and a bright red colour, making it easily distinguishable from the agar background.