The reaction of L-glutamic acid di tert-butyl ester (I) with 4-nitrophenyl chloroformate (II) by means of triethylamine in dichloromethane gives the corresponding carbamate (III), which is treated with 4-methoxythiophenol (IV) in dichloromethane to afford the thiocarbamate (V). Finally, this compound is treated with HCl.