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A methanol solution (15 ml) containing sodium sulfide. 9 hydrate (3.60 g) was added to 2-nitro-4-thiocyanophenol (1.96 g), which was prepared according to the method described in U.S. Pat. No. 2,562,948 (1951), in dimethyl sulfoxide (10 ml). Then N-(2-bromoethyl)phthalimide (2.54 g) was added, and the mixture was agitated for 3 hrs at room temperature, and was poured into ice water. The pH of the solution was adjusted to 5 with diluted hydrochloric acid, and the precipitate was collected to obtain N-[2-(4-hydroxy-3-nitrophenylthio)ethyl]phthalimide (2.3 g). The compound (3.5 g) was subjected to reduction under increased pressure at 70 atm in the presence of a 5% palladium carbon catalyst, and was subsequently caused to react with cyanogen bromide to yield 2-amino-5-[2-<2-(1,3-(2H)-dioxo-1H-isoindolyl)>ethylthio]benzoxazole (2 g). The benzoxazole derivative (2 g) was heated with hydrazine hydrate to yield 2-amino-5-(2-aminoethylthio)benzoxazole (1.1 g).

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