PRODUCTION OF 2-PIPERAZINECARBOXYLIC ACID SALT

摘要

PROBLEM TO BE SOLVED: To provide a method for producing the subject compound by which the compound useful for an intermediate for a medicine or an agrochemical is produced in high yield while keeping the optical purity by heating a piperazinecarboxylic acid derivative in an acidic aqueous solution. SOLUTION: A 2-piperazinecarboxylic acid derivative of formula I [R<1> and R<2> are each a 1-4C alkyl or H; X is an inorganic acid or an organic acid; (n) is 0-2], (preferably N-tert-butyl-2-piperazinecarboxamide of formula II) is heated in an acidic aqueous solution preferably to 60-90 deg.C for 1-10 hr, and a poor solvent (e.g. ethanol) is added to the resultant reaction mixture to precipitate 2-piperazinecarboxylic acid salt of formula III [Y is an inorganic acid or an organic acid; (m) is 1-2] in the method for producing the 2-piperazinecarboxylic acid salt. The acid in the acidic solution is preferably the inorganic acid such as hydrochloric acid and sulfuric acid used in an amount of 10-20 molar times as much as the compound of formula I. The concentration of the acid is >=20 wt.% in the case of the hydrochloric acid or 50-70 wt.% in the case of sulfuric acid.