Fluorous-Phase- and Chiral-Axis-Enhanced Fluorescent Sensitivity and Chemoselectivity for Cysteine Recognition

Highly fluorinated naphthyl aldehyde 1 and binaphthyl aldehyde (R)-2 were designed and synthesized for fluorous-phase-based sensing. Greatly enhanced sensitivity and chemoselectivity in going from 1 to (R)-2 in the fluorescent detection of cysteine has been discovered. This is attributed to the increased structural rigidity of the axially chiral binaphthyl unit in (R)-2 upon reaction with cysteine to form the corresponding thiazolidine product. The fluorous-phase-based detection of cysteine not only can allow the analysis to be conducted in a phase away from the interference of other organic and inorganic species but also results in significantly increased fluorescence response.