Reacción #1694324

Ecuación de reacción

t-Butoxycarbonyl-D-methionine

pentachlorophenol

dicyclohexylcarbodiimide

→

t-butoxycarbonyl-D-methionine pentachlorophenyl ester

Rendimiento 81.4%

Disolventes

ethyl acetate

Condiciones de reacción

Tratamiento posterior

1. 1
   FiltraciónAfter 2.5 h the solution is filtered after 2.5 h
2. 2
   Otrothe filtrate evaporated to dryness
3. 3
   OtroThe residue is recrystallised from hot methanol

Procedimiento

t-Butoxycarbonyl-D-methionine (20 g, 80.22 mmol) is added to a solution of pentachlorophenol (21.37 g) and dicyclohexylcarbodiimide (16.55 g, 80.3 mmol) in ethyl acetate (200 ml). After 2.5 h the solution is filtered after 2.5 h and the filtrate evaporated to dryness. The residue is recrystallised from hot methanol to give t-butoxycarbonyl-D-methionine pentachlorophenyl ester (32.5 g, 81.4%). A sample of this material (1.03 g, 2.14 mmol) is dissolved in DMF (10 ml) and to this solution is added hydroxylamine hydrochloride (0.149 g, 2.16 mmol) and diisopropylethylamine (0.91 ml, 5.2 mmol). After 16 h at room temperature the solvent is removed by evaporation and the residue partitioned between diethyl ether and 5% aqueous sodium carbonate. The aqueous phase (together with an insoluble oil which forms at the interface) is acidified by addition of citric acid to pH 6 and the product extracted twice with ethyl acetate. The combined ethyl acetate phases are washed successively with water and brine then dried over sodium sulfate. After the solvent is removed by evaporation the product is obtained as a crystalline solid by addition of a small amount of diethyl ether. A sample is recrystallised from ethyl acetate/hexane. mp 133°-134° C. 1H NMR δ (CDCl3) 8.50 (1H, broad s, --NH--), 5.58 (1H, m, urethane NH), 4.23 (1H, m, α--CH), 2.56 (H, m, γCH2), 2.09 (3H, s, S--CH3), 2.03 (1H, m, CH--CHAHB), 1.91 (1H, m, CH--CHAHB), 1.43 (9H, s, C(CH3)3); m/e (EI+) 265 (M+1), (CI-) 2.63 (M-1).

Fuente