The invention relates to a method of preparing multi-modal anion-exchange ligands, which comprises providing a cyclic three-functional scaffold comprising an amine, a carbonyl and a thiol; optionally derivatisation of the amine of the scaffold to provide an anion-exchanging group and/or to protect the amine; and aminolysis to open up the derivative by adding a reagent comprising an amine coupled to a residue R in order to add said amine to the carbonyl carbon of the opened scaffold. The scaffold is advantageously homocysteine thiolactone. In one embodiment, the method comprises an additional step of immobilising the opened scaffold to a base matrix to provide a separation medium, such as a chromatography medium.