Highly selective fluorescent sensor for homocysteine and cysteine

A new fluorescent sensor (1) based on a coumarin was synthesized for the selective detection of homocysteine (Hcy) and cysteine (Cys). The chemosensor has shown a selective response to Hcy or Cys over other various amino acids via a ring formation of thiazinane or thiazolidine. When Hcy or Cys was added, the fluorescent intensity of 1 was completely quenched through a photo-induced electron transfer with the sensitivity of sub-millimolar concentration.