Macropolycycles

This remarkable group of compounds was introduced by Lehn and his co-workers in Strasbourg . They are macrobi-, macrotri-, or macropolycyclic compounds which are similar to the in-out amines illustrated above, but they have crown-like bridges throughout. Because of their ability not only to complex cations but to encapsulate... 

In other sections in this chapter, we have referred to a variety of macropolycyclic structures which are more elaborate than the simple three-stranded bicyclic cryptands. This includes bridged double-macrocycles " , in-out bicyclic amines and the macrotricyclic quaternary ammonium salts of Schmidtchen. In addition to these, there are two other types of compounds which deserve special note. The first of these is a stacked twin-ring cryptand, but it is a hybrid molecule rather than a double-cryptand . The species shown below as 20 is a crowned porphyrin, and was designed to provide a pair of metal cation binding sites similar to those which might be available in natural biological systems . 

Cryptates the chemistry of macropolycyclic inclusion complexes. J. M. Lehn, Acc. Chem. Res.,... 

Macropolycyclic ligands, 2,942 classification, 2,917 metal complexes binding sites, 2, 922 cavity size, 2,924 chirality, 2, 924 conformation, 2,923 dimensionality, 2, 924 electronic effects, 2, 922 shaping groups, 2,923 structural effects, 2,922 molecular cation complexes, 2,947 molecular neutral complexes, 2,952 multidentate, 2,915-953 nomenclature, 2,920 Macro tetrolide actins metal complexes, 2,973 Macrotricycles anionic complexes, 2,951 cylindrical... 

Multidentate Macrocyclic and Macropolycyclic Ligands 22 Ligands of Biological Importance... 

Keywords stepwise construction, macropolycyclic compounds, bisdienophile, furan, bisdienes... 

Kohnke, F.H., Mathias, J.P., and Stoddart, J.F. Substrate-Directed Synthesis The Rapid Assembly of Novel Macropolycyclic Structures via Stereoregular Diels-Alder Oligomerizations. 165, 1-69 (1993). 

Polyammonium-containing ligands, 24 44 Polyammonium macropolycycles, 76 780 Polyampholytes, 20 475 479 solution properties of, 20 479 synthesis of, 20 477- 478 Poly(anhydrides), bioresorbable polymers, 3 740... 

A number of organic molecules capable of efficiently operating as phase-transfer catalysts is now available. The reaction mechanism both for soluble and polymer-supported systems is completely understood and the factors ruling the reactivity are recognised. The drawback of soluble catalysts is their difficult separation from the reaction products which in the case of the expensive macropolycyclic ligands imposes severe limitations in their use on a large scale. The cheap and easy to synthesize ammonium quaternary salts, providing they are stable under the reaction conditions, represent the catalysts of choice. 

The hrst opticaUy active macrobicycles and macropolycycles were repotted by Lehn and co-woricers (187) in 1974. Employing the synthetic methodology developed in Strasbourg for the preparation of cryptands, chiral molecular receptors, such as (5)-191 and (5)-192, have been isolated and characterized. 

Fascinating macrocyclic receptor cages based on a triaza-18-crown-6 derivative (79) and on a rigid cyclotriveratiylene unit (188) can be synthesized (189) by cormecting the two residues via three bridges in a single step. Macropolycycles, such as ( )-193 have been reported (189), and since the cyclotrivera-trylene unit is chiral and has been resolved (188), the preparation of optically active macrocyclic receptor cage molecules should be feasible (see below). 

The free macropolycyclic receptor (SS)-208 consisting of two l,l -tetralyl units bridged by four polyether chains between their 2 and 3 positions (211). 

Assembly of Novel Macropolycyclic Structures via Stereoregular Diels-Alder Oligomerizations. 165, 1-69 (1993). 

Crown ethers and cryptands show much of the same functional group chemistry as simple ether- or amine-containing molecules. The remarkable reactivity of these macropolycyclic species is primarily derived not from the composition of functional groups but from their three-dimensional arrangement. The important property of strong cation complexation is determined by the topology of the cavity defined by the ether and amine groups in the molecular superstructure. 

Larger anionic species such as sulfate, carboxylate and phosphate necessitate the preparation of larger macropolycycles as receptors. 

The various possible strategies for the synthesis of macropolycyclic cryptands are outlined in Figure 14. 

Interest in crown ethers has exploded since the initial discovery by Pedersen. With the addition of cryptands and other macropolycycles to the armory of coordination chemists there has been feverish activity to seek out new areas in which new and original uses can be devised. Now all branches of chemistry, polymer science, pharmaceutics and industrial processes have been touched by the crown ether revolution. 

The term bimacrocyck will be used instead of macrobicycle because bimacrocycles often also contain smaller rings (e.g. aryl rings). Then they are macropolycyclic although only two macrocycies exist. (In addition, no bicycle company has offered a sponsorship yet )... 

In order to construct a hydrophobic three-dimensional cavity that is in-tramolecularly limited in space, we have prepared cage-type cyclophanes by linking macrocyclic rings. First we prepared a macropolycyclic host, which is constructed with two rigid macrocyclic skeletons of different size, tetraaza[3.3.3.3]paracyclophane as the larger one and tetraazacyclotetradecane as the smaller one, and four flexible hydrocarbon chains that connect the two macrocycles [40]. The flexibility of four hydrocarbon chains connecting the two macrocycles allows the induced-fit host-guest interaction in aqueous media. 

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