A trifluoroacetic acid-labile sulfonate protecting group and its use in the synthesis of a near-IR fluorophore.

Sulfonated molecules exhibit high water solubility, a property that is valuable for many biological applications but often complicates their synthesis and purification. Here we report a sulfonate protecting group that is resistant to nucleophilic attack but readily removed with trifluoroacetic acid (TFA). The use of this protecting group improved the synthesis of a sulfonated near-IR fluorophore and the mild deprotection conditions allowed isolation of the product without requiring chromatography.