the present invention relates to novel key intermediates for the production of biologically active compounds coupled to polymers , of the general formula p -- ncx 2 , wherein x designates a halogen atom selected from chlorine and bromine , and wherein p designates the polymer backbone of a polymer of the polyamide , polyester and ureaformaldehyde type . the invention further relates to compounds obtained by the reaction of the above compound p -- ncx 2 with a bifunctional or polyfunctional nucleophile . suitable nucleophiles are hydrazides of dicarboxylic acids and amongst these there may be mentioned polyacrylamides partially substituted with acylhydrazide groups ; polyfunctional amines selected from alkylamines , aralkylamines , arylamines and macromolecular compounds containing amino groups . the key intermediate pncx 2 may be coupled directly to biologically active macromolecules and amongst the preferred compounds of this type there are the various biologically active proteins and enzymes . the coupling of the biologically active macromolecules may also be effected via hydrophilic polymer moieties first grafted onto the polymer p via said dihaloisocyanide groups .