N-Boc-L-tert-Leucine

20859-02-3

24424-99-5

62965-35-9

Step A: Synthesis of N-Boc-L-tert-Leucine 1. add triethylamine (56mL, 0.4mol) to a methanol (150mL) suspension of L-tert-leucine (26.1g, 0.2mol) at 0°C. 2. slowly add di-tert-butyl dicarbonate (48g, 0.22mol) to a methanol (40mL) solution of N-Boc-L-tert-leucine. 2. a solution of di-tert-butyl dicarbonate (48 g, 0.22 mol) in methanol (40 mL) was added slowly to the above mixture, controlling the reaction temperature between 0 and 5°C. 3. The reaction mixture was stirred at room temperature overnight. 4. Upon completion of the reaction, the solvent was removed under vacuum. 5. The residue was dissolved in ethyl acetate (200 mL) and the organic layer was washed with 10% w/v aqueous citric acid (3 x 100 mL). 6. The organic layer was dried with anhydrous magnesium sulfate, filtered and the solvent was removed in vacuum to afford N-Boc-L-tert-leucine as a light yellow oil (48.9 g, yield >100% with residual solvent). Product characterization: 1H NMR (CDCl3): δ/ppm 9.20 (1H, bs, NH), 5.10 (1H, m, CH), 4.15 (1H, m, CH), 1.45 (9H, s, tert-butyl in Boc), 1.00 (9H, s, tert-butyl in tert-leucine).