(Step 8-ii) A mixture of (R)-benzyl 1-(5-mercapto-4-amino-4H-1,2,4-triazol-3-yl)ethylcarbamate (1.32 g, 4.5 mmol) in ethanol (15 mL) was heated to 80° C. and 3-chlorophenylisothiocyanate (1.3 g, 7.65 mmol) and dicyclohexylcarbodiimide (1.11 g, 5.4 mmol) were added. After 4 hours, the reaction was cooled, diluted with an equal volume of ether, and filtered. The filter cake was washed with additional ether and the collected solids dried in vacuo to provide 0.94 g of (R)-benzyl 1-(6-(3-chlorophenylamino)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)ethylcarbamate: ESMS MH+=429.
