The alkylation of succinimide (I) with 1,2-dibromoethane (II) by means of K2CO3 in refluxing butanone gives N-(2-bromoethyl)succinimide (III), which is condensed with 4-hydroxythiophenol (IV) by means of K2CO3 in refluxing ethanol to afford 4-hydroxyphenyl 2-succinimidoethyl sulfide (V). Finally, this compound is esterified with 4-guanidinobenzoyl chloride in pyridine, and treated with methanesulfonic acid in methanol.