2,4-dinitrophenol (Labteh)
(S)-2-methylbutanoic acid (Sigma)
N,N-dicyclohexylcarbodiimide DCC (Sigma)
Ethyl acetate (Irea)
Petroleum ether 40-60°C (Irea)
Dichloromethane (Irea)
Silica gel

2,4-dinitrophenol (0.4484 g, 2.44 mmol) and (S)-2-methylbutanoic acid (0.265 ml, 2.43 mmol) of  were dissolved in dry ethyl acetate (4 ml) and cooled in ice bath. DCC (0.5074 g, 2.46 mmol) of was dissolved in dry ethyl acetate (4 ml) and was added to above solution in one portion under vigorous stirring. The reaction mixture was stirred for 1 h with cooling and 19 h at room temperature. The precipitated N,N-dicyclohexylurea was filtered off and the solvent was removed from the filtrate on rotary evaporator. The yellow oil thus obtained was purified with column chromatography. Eluent: petroleum ether:DCM:ethyl acetate 5:1:1. Product obatained as yellow oil that slowly solidifies in refrigerator. Yield 100% (650.1 mg).

Yellow solid.
[α]d20 +16.6° (c 0.54, EtOAc).
1H-NMR (400MHz, CDCl3, δ, ppm): 1.05 (t, 3H, J 7.4Hz), 1.36 (d, 3H, 3J = 7Hz), 1.66 (dt, 1H, 3J = 14.1Hz, 3J = 7Hz), 1.9 (dt, 1H, 3J = 14.1 Hz, 3J = 7.2Hz), 2.75 (sext, 1H, 3J = 6.9Hz), 7.46 (d, 1H, 3J = 8.9Hz), 8.51 (dd, 1H, 3J = 8.9Hz, 3J = 2.7Hz), 8.94 (d, 1H, 3J = 2.6Hz).

V. K. Kibirev, A. A. Gershkovich Sintez peptidov. Reagenty i metody (in Russian) // Kiev, 1987, p. 59.