RACEMIZATION OF AMINOKETONE DERIVATIVE

摘要

PURPOSE: To recover an aminoketone derivative by racemization from an unnecessary optically active aminoketone derivative prepared after optical resolution of an optically active aminoketone derivative having central muscle relaxation activity and to reuse the aminoketone derivative. CONSTITUTION: This derivative is shown by formula I (R<1> is a group of a formula II; R<2> is an alkyl, etc.; R<3> and R<4> are each pyrrolidine, etc.; R<5> is a halogen, etc.). The derivative, for example, is obtained by dissolving (-)-3- phenyl-5- 2(pyrrolidinylmethyl)butyryl}isoxazole hydrichloride in water and neutralizing the solution with an alkali such as sodium carbonate to give a solution of the subject liberated optically active derivative in an organic solvent such as ethyl acetate. The organic solvent layer of the solution is treated with an aqueous solution of a weak acid having preferably >=4 pKa value at 0-60 deg.C for several hours to form a propenone derivative of formula III. After the separation of the organic solvent solution, an amine of formula IV is added thereto and the propenone derivative is reacted with the amine to be racemized to give the objective derivative. The concentration of the subject derivative in the organic solvent is 10-30wt.% and that of the aqueous solution of the weak acid is preferably 1-50wt.%.