The discovery in 1954 of the selective reactions of boronic acids with proximal diols, and subsequent studies of other bi-functional substrates, affording cyclic derivatives, opened a new field in studying the chemical properties of these polyfunctional compounds. A wide range of specific boronates has been prepared, and many workers have shown how useful they can be for example, as crystalline derivatives, reagents for structural analysis, intermediates in synthesis, derivatives for use in a range of separatory techniques, and reaction catalysts. Boronic acids and their derivatives are also of potential value in cancer therapy and possibly as hormone analogues.