The present invention relates to a method for preparing conjugates of an active substance and hydroxy alkyl starch and to conjugates of an active substance and hydroxyalkyl starch, preferably hydroxy ethyl starch, wherein the conjugates are prepared by covalently linking the hydroxyalkyl starch and the active substance by a chemical residue having a structure according to formula (I) (I’) (I’’) wherein R, R, R, R, Rand R4 are independently selected from the group consisting of hydrogen, an optionally suitably substituted, linear, cyclic and/or branched alkyl, aryl, heteroaryl, aralkyl, and heteroaralkyl group, preferably hydrogen.
