Citric Acid → N-(2-{[(Benzyloxy)(hydroxy)methylidene]amino}-1-hydroxy-3-methylpentylidene)glycine

Participants

Reaction Steps

2.23 g of Z-Ile-OH-dicyclohexylammonium salt are suspended in ethyl acetate and acidified with 0.2 M citric acid. The resulting ethyl acetate solution is washed until neutral, dried and evaporated to dryness. The residue is dissolved in 15 ml of acetonitrile, and 750 mg of H-Gly-OMe.HCl are added to the solution followed at 0° C., with stirring, by 0.84 ml of triethylamine. After 10 minutes 1.24 g of dicyclohexylcarbodiimide are added and the mixture is stirred overnight at 0° C. The precipitate is filtered off, the filtrate evaporated to dryness, and the residue taken up in 30 ml of ethyl acetate and filtered. The ethyl acetate solution is washed with 0.2 M citric acid and saturated sodium bicarbonate solution, dried and concentrated to about 10 ml in vacuo. After adding 25 ml of hexane the protected dipeptide crystallises out; melting point 120°-122° C. Rf = 0.53 in the system chloroform-methanol (95:5) in a thin layer chromatogram on silica gel.

Provenance & Evidence