The invention relates to a crosslinked hyaluronan derivative in the form of a hydrogel or microfibers, and to a method of preparation thereof, consisting in a C—C coupling reaction. The C—C coupling reaction is performed via reaction of a hyaluronan derivative carrying a terminal aryl-halide and/or aryl-borate group, and a hyaluronan derivative carrying an alkenyl or alkynyl group, in water, phosphates buffer or a mixture of an organic acid and an alcohol, and in the presence of a palladium active catalyst. The palladium active catalyst may be e.g. a complex of palladium (II) acetate and an inorganic or organic base, or a complex of palladium (II) and 2-amino-4,6-dihydroxypyrimidine.