(Fluoren-9-ylmethoxy)carbonyl (Fmoc) amino acid azides: Synthesis, isolation, characterisation, stability and application to synthesis of peptides

The synthesis of Fmoc amino acid azides starting from the corresponding protected amino acid and sodium azide (NaN3) by the mixed anhydride method using isobutoxycarbonyl chloride (IBC-Cl) or by the acid chloride method is described. Isolated as crystalline solids, they are stable at room temperature, with a long shelf-life, as well as in aqueous washing operations. They are useful as coupling agents in peptide synthesis.