Methanol → L-tyrosyl-D-alanyl-glycyl-L-phenylalanyl-L-norleucine

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Reaction Steps

1.15 g. (1.6 mmoles) of Z-Tyr-D-Ala-Gly-Phe-Nle-OMe (3rd step of Example 1) are suspended in a mixture of 4 ml. of methanol and 2 ml. of acetone, then saponified with 0.5N sodium hydroxide in the presence of thymolphthalein as indicator. When the alkali consumption becomes slower, the mixture is diluted with 10 ml. of water and shaken with 3×5 ml. of ethyl acetate. On evaporating the ethyl acetate phases 0.3 g. (26%) of protected pentapeptide ester is recovered. The aqueous phase is acidified with 0.5N sulphuric acid, the precipitated substance (Rf2 0.25-0.35) suspended in 50 ml. of 80% acetic acid and hydrogenated in the presence of palladium catalyst. In the course of the reaction the substance is dissolved. At the end of the reaction the catalyst is filtered off, the solution evaporated and the residue rubbed with about 4 ml. of cold water. The formed crystalline substance is filtered, washed with cold water and dried. Yield: 0.47 g. (70%) of the named product; Rf4 0.19-0.23. Aminoacid analysis: Gly=1.0, Ala=1.02; Nle=1.02; Tyr=0.98; Phe=1 (reference basis).

Provenance & Evidence