[p-Sulfotetrafluorophenyl hydrophilic activated esters of amino acids in peptide synthesis]

Highly reactive hydrophilic (i.e., water-soluble) p-sulfotetrafluorophenyl esters (Tfs esters) are proposed for peptide synthesis in aqueous and aqueous-organic media, as well as for protein and peptide partial synthesis in an aqueous medium. These esters can serve as a basis for creating a series of protein modifying reagents. As they are analogs of the widely used pentafluorophenyl esters, the Tfs esters possess a high reactivity coupled with good stability during storage. The expression for the reaction rate (for substrates AA1 and AA2) is shown to be v = k[Boc-AA1-OTfs][H-AA2-NH2]0.5 for both water and DMF, i.e., the reaction is not a simple second-order reaction. The reaction rate in water is only slightly lower than that in DMF.