A new reagent, 2-[phenyl(methyl)sulfonio]ethyl-4-nitro-phenylcarbonate tetrafluoroborate (Pms-ONp), for preparing water-soluble N-protected amino acids

Peptide syntheses are performed in various organic solvents, the disposal of which is an environmental problem. To avoid this problem, peptide synthesis in water using reagents of low toxicity is desirable. For peptide synthesis in water, we previously reported the design of a water-soluble N-protecting group, 2-[phenyl(methyl)sulfonio]ethoxycarbonyl tetrafluoroborate (Pms) group, but the introduction of this group onto sulfur-containing amino acids was problematic. Here, a new reagent, 2-[phenyl(methyl)sulfonio]ethyl-4-nitrophenylcarbonate tetrafluoroborate (Pms-ONp), has been designed and used to prepare Pms derivatives of sulfur-containing amino acids. Pms-Met was prepared and tested for the solid-phase synthesis of Met-enkephalin amide in water using a crosslinked ethoxylate acrylate resin.