Trifluoroacetic acid → L-valyl L-valine methyl ester trifluoroacetate

Participants

Reaction Steps

N-tert-butoxycarbonyl L-valyl L-valine methyl ester (16.47 g, 49.85 mmol) was treated with a 50% (v/v) solution of TFA in CH2Cl2 (130 mL). The reaction mixture was stirred for 2 h at room temperature before the solvent and bulk of excess TFA were evaporated. Portions of CH2Cl2 (3×100 mL) and purified CHCl3 (6×200 mL) were added and evaporated. The residue (19.17 g) was washed with Et2O (2×80 mL) and the Et2O decanted off. An additional 80 mL Et2O was added and the suspension filtered. The collected solid was washed with Et2O (80 mL) and dried; δH (300 MHz; d6-DMSO) 8.62 (1H, d, J 7, NH), 8.17 (3H, br s, NH3+), 4.19 (1H, dd, J 7 and 6, CαH(Val2)), 3.75 (1H, br d, J 5, CαH(Val1)), 3.64 (3H, s, OCH3), 2.16-2.01 (2H, m, CH(CH3)2), 0.96-0.90 (12H, m, CH(CH3)2); δC (75 MHz; d6-DMSO) 171.4, 168.4, 158.4 (q, JCF 31), 117.1 (q, JCF 297) 57.7, 56.9, 51.7, 29.9, 29.6, 18.8, 18.1, 18.1, 17.4

Provenance & Evidence