The present application discloses a method of modifying a macromolecule, the method comprising the steps of (i) providing the macromolecule; (ii) providing a compound of the general formula (I): wherein N is a primary amino group protected with the protecting group P, wherein the protecting group involves both free valences of the primary amino group; m is an integer of 1-12 and n is an integer of 1-2000; R1 and R2 are independently selected from the group consisting of hydrogen and C1-4-alkyl; and X is a reactive group; and (iii) allowing the compound of the general formula (I) to react with the macromolecule so as to form grafts on the macromolecule. Compounds of the general formula (i) and a method for the preparation thereof are also disclosed.