Reacción #54607

Ecuación de reacción

chlorine tolidine

Ac-Ser(Bzl)-Asp(OBzl)-Ala-Ala-OBzl

MeOH

H2O

→

desired product

Rendimiento 86.3%

Ac-Ser-Asp-Ala-Ala-OH

Rendimiento 86.3%

Disolventes

n-BuOH HOAc EtOAc H2O

HOAc

Condiciones de reacción

Tratamiento posterior

1. 1
   FiltraciónThe catalyst was filtered off
2. 2
   Concentraciónthe filtrate concentrated to a smaller volume
3. 3
   Otroto give 0.38 g crude material
4. 4
   workup.ADDITIONin addition to the major component
5. 5
   OtroThe compound was then purified on a Bio-Rad AGl×2 column (3×24 cm) which
6. 6
   Lavadowas washed with 0.2 M NaOH, H2O, 0.2 M HOAc
7. 7
   Lavadothe column eluted with 250 ml each of the following acetic acid solutions in the order of: 0.25 M, 0.5 M, 1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M, 4.0 M, and 4.5 M
8. 8
   Otroeach 10 ml fraction was collected into an LKB fraction collector
9. 9
   Otroget tlc plate (Merck 60, F-254)
10. 10
    workup.ADDITIONThe fractions containing the major component

Procedimiento

Ac-Ser(Bzl)-Asp(OBzl)-Ala-Ala-OBzl (0.6 g, 0.888 mmol) was hydrogenated in a Parr apparatus at 50 psi in the presence of 0.62 g catalyst (5% Pd on BaSO4) in a solvent mixture consisting of 35 ml MeOH, 15 ml H2O, and 1 ml HOAc for 4 hours. The catalyst was filtered off and the filtrate concentrated to a smaller volume and lyophilized to give 0.38 g crude material. Tlc showed two minor contaminants in addition to the major component. The compound was then purified on a Bio-Rad AGl×2 column (3×24 cm) which was washed with 0.2 M NaOH, H2O, 0.2 M HOAc, and equilibrated with pH 8.5 buffer of 0.025 M ammonium acetate. The sample was applied at this pH and the column eluted with 250 ml each of the following acetic acid solutions in the order of: 0.25 M, 0.5 M, 1.0 M, 1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M, 4.0 M, and 4.5 M. The flow rate was adjusted to approximately 50 ml/hr and each 10 ml fraction was collected into an LKB fraction collector. The compound was located by spotting a 5 μl portion from each tube on silica get tlc plate (Merck 60, F-254) and developed in the solvent system of n-BuOH:HOAc:EtOAc:H2O (1:1:1:1) and then stained with chlorine-tolidine reaction. The fractions containing the major component were pooled and lyophilized twice to give 310 mg (86.3%) of the desired product; [α]D25 =-77.01° (c 1, 10% HOAc).

Fuente