An efficient approach to the synthesis of water-soluble cyanine dyes using poly(ethylene glycol) as a soluble support

An efficient synthesis approach to unsymmetrical water-soluble cyanine dyes has been established. Loading and activation of sulfoindolenium to poly(ethylene glycol) (PEG) have been achieved via a simple strategy. Cyanine dyes are released by the attack of heterocyclic carbon nucleophile and the cleavage of PEG-bound hemicyanine. The efficient approach delivers cyanine dyes in high purity without the nontrivial chromatographic separation.