2-Piperazinecarboxylic acid derivatives

Piperazinecarboxylic acid derivatives are interesting intermediates, e.g., for Crixivan, the well-known HIV protease inhibitor of Merck. The Rh/josiphos-catalyzed hydrogenation of a substituted cyclic enamide was used by Lonza [38] to produce >200 kg of the piperazine intermediate depicted in Scheme 11. A related catalyst was successfully employed by Merck [39] to pilot the hydrogenation of... 

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