Hydrochloric Acid → Ammonium Hydroxide

Participants

Reaction Steps

Stir 10.5 g of S-benzyl-L-cysteine and 11.0 g of 2-oxo-4-phenylbutyric acid, ethyl ester in 1000 ml of absolute ethanol at room temperature for 24 hours. Add 5.28 g of sodium cyanoborohydride and stir the resulting mixture at room temperature for 48 hours. Concentrate this mixture in vacuo at 30° C. to give a white residue. Suspend the residue in ice-water, add concentrated hydrochloric acid to maintain pH 2-4, and stir this mixture for 11/2-2 hours. Absorb this aqueous solution on XAD-2 (Rohm & Haas Co.) resin. Elute the resin with water and then with absolute ethanol. Concentrate the ethanol solution and chromatograph the residue on a column of silica gel using chloroform:isopropanol:7% ammonium hydroxide 1:1:1 (organic layer) to give N-[1(S)-carboethoxy-3-phenylpropyl]-S-benzyl-(R)-cysteine.

Provenance & Evidence