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EXAMPLE 89 1.455 g of the product of Example 58 in 45 ml of ethanol were treated with 364 mg of thiourea and the mixture was heated at reflux for 18 hours. After cooling the precipitate was filtered off and washed with ethanol and with diethyl ether. The solid was dried to give 1.33 g of 3-[1-[3-(amidinothio)propyl]-3-indolyl]-4-(1-methyl-3-indolyl)-1H-pyrrole-2,5-dione methanesulphonate, m.p. 236-238 C. (decomposition).