(S)-2-Aminonon-8-enoic acid (1.5 g, 1.0 eq.) and di-tert-butyl dicarbonate (2.01 g, 1.05 eq.) were reacted in a solvent mixture of THF/H2O (7.5 mL/2.5 mL) in the presence of triethylamine (TEA, 2.2 g, 2.5 eq.) for 5 h at 15-25°C. After completion of the reaction, ethyl acetate (EA, 5 mL) was added. After completion of the reaction, ethyl acetate (EA, 5 mL) was added and the pH was adjusted to 6.5 with 2N HCl. After phase separation, the aqueous phase was extracted with ethyl acetate (5 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, filtered and the solvent was concentrated to give (S)-2-((tert-butoxycarbonyl)amino)nona-8-enoic acid as a white solid 2.02 g in 85% yield.