ABSTRACT
U.S. Patents 3,651,157 and 3,676,508 (1972). 41. W. Riemenschneider (Hoechst AG), U.S. Patent 3,845,148 (1974). 42. H. Gerstenberg, H. Krekeler, H. Osterbrink, and W. Riemenschneider (Hoechst
AG), West German Patent 2,218,414 (1974). 43. R. Walburg, H. Gerstenberg, and H. Osterbrink (Hoechst AG), U.S. Patent
3,918,919 (1975). 44. W. Riemenschneider, L. Hornig, H. Meidert, and H. Krekeler (Hoechst AG),
U.S. Patent 3,928,479 (1975). 45. W. Riemenschneider, H. Krekeler, and H. Meidert (Hoechst AG), U.S. Patent
3,931,309 (1976). 46. D. Rebhan, H. Krekeler, and H. Schmitz (Hoechst AG), DOS 2,444,783 (1976).
Considerable interest in clathrates and similar systems has arisen over the past few decades. Scientifically, the extremely high shape-selectivity of inclusion compounds is attractive. Subtle shape differences between molecules can be sensed down to atomic dimensions. This is reminiscent of the high selectivities observed in studies of enzyme action, and indeed is explained in both instances by the same "lock and key" hypothesis of Emil Fischer: the two components must fit together as a key fits a lock or the clathrate (or enzyme-substrate complex in biological systems) cannot form. Clathration normally does not
involve chemical reaction, and therefore may be regarded as a simplification of the enzyme specificity problem. Components of c1athrating systems are often much simpler molecular species than the high molecular weight protein enzymes, and consequently lend themselves to easier characterization; for example, by single crystal X-ray analysis. The analogy does not lead one directly to the solution of problems in enzyme action, so clathrate systems are normally studied as independent examples of molecular shape specificity.
