HCID 178418361, 화합물 → Carnosine

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A 1-litre pressure autoclave was initially charged with 1.76 g of Rh/C (0.4 mol % pure Rh, based on reactant used) in a mixture of 94.2 g of ammonia solution (25% in H2O) and 62.8 g of methanol. The autoclave was closed, and the contents were heated to 90° C. and the autoclave was pressurized with 40 bar of hydrogen. A, solution of 20.0 g (0.09 mol) of (S)-2-(cyanoacetyl-amino)-3-(1H-imidazol-4-yl)propionic acid (prepared according to Example 3) in a mixture of 94.2 g of ammonia solution (25% in H2O) and 62.8 g of methanol was then metered in over the course of one hour. After further reaction at 90° C. for one hour, the reaction mixture was cooled to room temperature. The autoclave was depressurized and the catalyst was filtered off via activated carbon. An in-process HPLC analysis showed that the clear greenish reaction solution (326.2 g) contained 5.74% (m/m) carnosine, corresponding to a selectivity of 92% for complete conversion. The reaction mixture was then concentrated to approx. 60 g in a rotary evaporator. Dropwise addition of 174 g of ethanol caused precipitation of a white solid which was filtered off and dried at 50° C./20 mbar.

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