t-Amyloxycarbonyl as a New Protecting Group in Peptide Synthesis. V. Direct Synthesis of t-Amyloxycarbonyl- and t-Butyloxycarbonyl-amino Acids Using the Respective t-Alkyl Chloroformates

Abstract t-Amyloxycarbonylamino acids (Aoc-amino acids) were found to be synthesizable under the conditions of the Schotten-Baumann reaction with t-amyl chloroformate in the presence of a water-soluble inert solvent. The procedure was applied to almost all amino acids or their derivatives; the yields of the products and their purities were satisfactory except in the cases of asparagine, glutamine, and nitroarginine. Many t-butyloxycarbonylamino acids (Boc-amino acids) were also synthesized successfully using the same procedure. Similarly, t-amyl and t-butyl carbazates were synthesized in satisfactory yields with these chloroformates and hydrazine hydrate. Thus, the procedure was demonstrated to be the simplest for the preparation of Aoc-or Boc-amino acids and hydrazide.