Revolutionary phosgene-free synthesis of α-amino acid N-carboxyanhydrides using diphenyl carbonate based on activation of α-amino acids by converting into imidazolium salts

Article abstract of DOI:10.1002/pola.24213

The phosgene-free synthesis of α-amino acid n-carboxyanhydrides using diphenyl carbonate based on activation of α-amino acids by converting into imidazolium salts was reported. 1-Ethyl-3-methylimidazolium bromide (4.77 g, 25.0 mmol) was dissolved in water (25 mL) and was passed through a column of Amberlite IRA 400 CL (50 cm³) using 250 mL of water as an eluent to synthesize amino acid imidazolium salt. A solution of L-phenylalanine imidazolium salt (550 mg, 2.0 mmol) in acetonitrile (15 mL) was added dropwise to a solution of diphenyl-carbonate (427 mg, 2.00 mmol) in acetonitrile (5 mL) at room temperature, and the reaction mixture was stirred at room temperature to synthesize urethane derivative. The results showed that all of the obtained imidazolium salts were soluble in chloroform, dichloromethane, 2-butanone acetonitrile, and not soluble in tetrahydrofuran.