, a hydrazine group, an acylhydrazide group, an azide group and an N-maleimide group; at least two of A, B and E are other than hydrogen; and R1 is an aliphatic group of at least two carbons or an aromatic group of at least six carbons; and the tag of the tagged polypeptide, tagged polyol, tagged polyolefin or tagged carbohydrate is a fluorescent chemical group, a dye, a radioactive group, a photo