N-Alkyl-2,3,3-trimethyl-3H-indoleninium-5-sulfonates as the initial raw material, the water-soluble asymmetrical squarylium indocyanine dyes were synthesized by two-step synthesis method and solid-phase synthesis method, respectively. In two-step synthesis method, a series of squarylium hemicyanine dyes were synthesized by condensation of squaric acid with various N-alkyl-2,3,3-trimethyl-3H- indoleninium-5-sulfonates, then the water-soluble asymmetrical squarylium indocyanine dyes were synthesized by condensation of squarylium hemicyanine dyes with another N-alkyl-2,3,3-trimethyl-3H- indoleninium-5-sulfonate. Solid-phase synthesis method mainly includes three steps. Firstly, squaric acid was linked to the solid-phase polymer support PEG with chemical bond using p-aminobenzoic acid as bridge. And then, squarylium hemicyanine dyes with solid-phase polymer support were synthesized by reaction of squaric acid linked solid-phase polymer support and N-alkyl-2,3,3-trimethyl-3H-indoleninium-5- sulfonates. Lastly, the water-soluble asymmetrical squarylium indocyanine dyes were gotten by condensation of squarylium hemicyanine dyes linked solid-phase polymer support with different indoleniniums and cuting off the solid-phase support from squarylium hemicyanine dyes. These raw dyes were purified by C-18 reverse phase column chromatograph. Their structures were confirmed by ¹H NMR and MS. The spectral properties of the title products were checked. In the process of synthesizing of water-soluble asymmetrical squarylium indocyanine, it is found that the yields of the title products by solid-phase synthesis method are 2 times of those of traditional two-step method. Solid-phase synthesis method is more suitable to synthesize water-soluble asymmetrial squarylium indocyanine dyes.

Key words: solid-phase synthesis, water-solubility, asymmetric indocyanine dyes, squaric acid