The present invention relates to a method for preparing conjugates of an active substance and hydroxyalkyl starch and to conjugates of an active substance and hydroxyalkyl starch, preferably hydroxyethyl 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) or formula (I') or formula (I") wherein R 1 , R 2 , R 2' , R 3 , R 3' and R 4 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.
