Avlane,J.A.S.M.,France,1981
1.1 g of methanesulfonic acid were added dropwise to a mixture of 4.6 g of 8-
nitro-1,2-dihydro-2-(N-methylpiperazin-1-yl)methylene-6-(o-chlorophenyl)-
1H,4H-imidazo-[1,2-a][1,4]benzodiazepin-1-one in 100 ml of anhydrous
methylene chloride and 5 ml of methanol. Dry ether was slowly added until
crystals formed on scratching and the solution was allowed to crystallize with
further ether being added to complete the crystallization. The pale yellow solid
was filtered off, washed with ether and crystallized from methylene chloridemethanol to obtain 5.4 g of 8-nitro-1,2-dihydro-2-(N-methylpiperazin-1-
yl)methylene-6-(o-chlorophenyl)-1H,4H-imidazo-[1,2-a][1,4]-benzodiazepin-1-
one methanesulfonate melting at 205°C to 210°C.
