Compound can be prepared in two similar ways both starting from 7-chloro-1,3-dihydro-5-(o-fluorophenyl)-2H-1,4-benzodiazepin-2-one-4-oxide (I): 1) The condensation of (I) with 2-bromoethanol (A) by means of NaH in DMF gives the N-hydroxyethyl derivative (II), which by refluxing with acetic anhydride is converted into 7-chloro-1,3-dihydro-1-(2-acetoxyethyl)-3-acetoxy-5-(o-fluorophenyl)-2H-1,4-benzodiazepin-2-one (III). Finally, (III) is deacetylated with methanolic ammonia. 2) The condensation of (I) with 2-bromoethylacetate (B) as before gives the N-acetoxyethyl derivative (IV), which by refluxing with acetic anhydride is converted into (III).