Fluorescent compounds

Preparation of 2-(anilinovinyl)-1-(5-carboxypentyl)-3,3-dimethyl-5-sulfoindolium, Potassium Salt (Compound No. 1

[0385]

[0386]A mixture of 1-(5-carboxypentyl)-2,3,3-trimethylindoleninium-5-sulfonate, potassium salt (Bioconjugate Chem. 4, 105 (1993)) (5 g), N,N′-diphenylformamidine (2.3 g) and acetic anhydride (1.1 mL) was heated at 120° C. for 30 minutes. After cooling down to room temperature, the mixture was concentrated to dryness under vacuum and the residue was purified by column chromatography on silica gel (3.5 g).

Preparation of 2-(4-anilinobutadienyl)-1-(5-carboxypentyl)-3,3-dimethyl-5-sulfoindolium, Potassium Salt (Compound No. 2)

[0387]

[0388]A mixture of 1-(5-carboxypentyl)-2,3,3-trimethylindoleninium-5-sulfonate, potassium salt (10 g), malonaldehyde dianil hydrochloride (8 g), Et3N (0.356 mL) in AcOH (40 mL) was heated at 120° C. for 3 hours. After cooling down to room temperature, the mixture was concentrated to dryness under vacuum and the residue was purified by column chromatography on silica gel to dark brown gummy solid (5 g).

Preparation of Compound Nos. 3a and 3b

[0389]

[0390]To a solution of 1-(5-carboxypentyl)-2,3,3-trimethylindoleninium-5-sulfonate, potassium salt (0.1 g) in DMF (1 mL) was added Et3N (0.1 mL) and TSTU (80 mg). The mixture was stirred at room temperature for 1 hour, followed by the addition of Et3N (40 μL) and m-dPEG24 amine (0.4 g) (QuantaBiodesign, Powell, Ohio) or m-dPEG12 amine (0.2 g) (QuantaBiodesign, Powell, Ohio). The mixture was stirred at room temperature overnight and then concentrated to dryness. The residue was purified by column chromatography on silica gel to give a light brown solid (250 mg for compound No. 3a and 102 mg for compound No. 3b).