Methods are provided for the production of bendamustine alkyl ester, bendamustine, as well as derivatives thereof. With the methods the production of these compounds is possible in reproducibly high yields. To this end, hydroxyl-group-containing esters are used as the starting material, whose hydroxyl groups are substituted in a simple way by halogen groups. This substitution is possible in the presence of (i) oxalyl chloride and (ii) dialkylformamide, dialkyl acetamide or dimethyl sulfoxide. In a subsequent reaction, the resulting esters can be hydrolyzed to form the acid.