Hydrochloric Acid → (R)-3-(1-Allyl-1H-imidazol-4-yl)-2-benzyloxycarbonylaminopropionic acid

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Reaction Steps

3.53 ml (4.24 g, 24.84 mmol) of benzyl chloroformate were added to a solution of 4.85 g (24.84 mmol) of (R)-3-(1-allyl-1H-imidazol-4-yl)-2-aminopropionic acid (as described for the (S)-enantiomer in Bioorg. Med. Chem. 2006, 14, 5981-5988) in 13 ml of 2N sodium hydroxide solution while stirring at 0° C., and stirring was continued at this temperature with addition of a further 13 ml of 2N sodium hydroxide solution for 2 h, and the mixture was them warmed to RT. The reaction mixture was covered with a layer of ethyl acetate, and the pH was adjusted to 3 to 4 with 6N hydrochloric acid. The organic phase was separated off, and the aqueous phase was washed again with ethyl acetate and then freeze dried. The residue was mixed with THF and DMF until stirrable and was thoroughly stirred, and the suspension was filtered. The resulting solution was concentrated and reacted without further purification in the next step.

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