122-75-8

64-19-7

140-28-3

122-75-8

S3. The mixed organic phase of Compound C with toluene obtained in step S2 was transferred to a three-necked flask and the fractions were removed by distillation. After the mixture was cooled to 30°C, it was dissolved in 200 g of ethyl acetate and heated to 60°C. Subsequently, 20 g of glacial acetic acid at 98% concentration was slowly added dropwise. After the dropwise addition was completed, the reaction conditions were maintained for 1.0 hour. Upon completion of the reaction, the mixture was slowly cooled and 49.5 g of the wet product (i.e., a hydrate containing N,N'-dibenzylethylenediamine diacetate) was collected by filtration. The wet product was dried at 45 °C to give 49.0 g of N,N'-dibenzylethylenediamine diacetate (i.e., compound D).