1-Methyl-5-(4-morpholinyl)-1H-benzimidazole-2-butanoic acid ; 4-(1-Methyl-5-morpholino-1H-benzo[d]imidazol-2-yl)butanoic Acid ; Bendamustine Ether Impurity ; Bendamustine Related Compound B (USP); 4-(1-Methyl-5-morpholino-1H-benzo[d]imidazol-2-yl)butanoic Acid; 4-(1-Methyl-5-morpholino-1H -benzimidazol-2-yl)butanoic Acid; Bendamustine Related Compound B (USP);