(rac)-1,2-Diaminopropane is resolved using (-)-L-tartaric acid. The bitartrate salt is treated with HCl to give the dihydrochloride salt, (-)-S-1,2-diaminopropane dihydrochloride (I). (I) in water is added to a solution of chloroacetic acid and sodium hydroxide below 20 C, and allowed to stand at room temperature for 7 days. After concentration and filtration, the product is isolated by passing the filtrate down an ion exchange column and eluting with water. The portion of the eluate containing the bulk of the optical activity is concentrated by heating. Crystals of (+)-(S)-1,2-propylene dinitrilotetraacetic acid (II) are obtained by filtration. (II) is heated under nitrogen for 20 h at 165 C to give (+)-(S)-1,2-di(piperazine-2,6-dione)propane.

(rac)-1,2-Diaminopropane is resolved using (-)-L-tartaric acid. The bitartrate salt is treated with HCl to give the dihydrochloride salt, (-)-S-1,2-diaminopropane dihydrochloride (I). (I) in water is added to a solution of chloroacetic acid and sodium hydroxide below 20 C, and allowed to stand at room temperature for 7 days. After concentration and filtration, the product is isolated by passing the filtrate down an ion exchange column and eluting with water. The portion of the eluate containing the bulk of the optical activity is concentrated by heating. Crystals of (+)-(S)-1,2-propylene dinitrilotetraacetic acid (II) are obtained by filtration. (II) is heated under nitrogen for 20 h at 165 C to give (+)-(S)-1,2-di(piperazine-2,6-dione)propane.