Basket-shaped molecules

Figure 4. The synthetic strategy for basket-shaped molecules 12 led to a simple one-step synthesis of the tetramethoxy-substituted [2]catenane 11.

Scheme 6 Schematic representation of the synthetic approach to basket-shaped molecules with...

A Newman-Kwart rearrangement of the O-thiocarbamoy I derivative of a thiacalix[4]arene results in the synthesis of thiacalix[2]thianthrenes 69. The two thianthrene units are linked by two sulfur bridges producing a basket-shaped molecule <07TL5401>. Treatment with... 

Fabrication needs also include the ability to combine organic and inorganic nanoparticles into hybrid materials. For example, organic clathrates, binders, and basket-shaped molecules - such as block copolymers and triblock polymers - may be combined with inorganic oxides, polyoxometaUates, and chemically aggressive porous materials to form useful hybrids. This is important in the development of countermeasures that can select, detect, and decontaminate a wide range of toxic materials. 

Supramolecular chemistry has been a very popular research topic for three decades now. Most applications are foreseen in sensors and opto-electronical devices. Supramolecular catalysis often refers to the combination of a catalyst with a synthetic receptor molecule that preorganizes the substrate-catalyst complex and has also been proposed as an important possible application. The concept, which has proven to be powerful in enzymes, has mainly been demonstrated by chemists that investigated hydrolysis reactions. Zinc and copper in combination with cyclodextrins as the receptor dramatically enhance the rate ofhydrolysis. So far, the ample research devoted to transition metal catalysis has not been extended to supramolecular transition metal catalysis. A rare example of such a supramolecular transition metal catalyst was the results of the joined efforts of the groups of Nolte and Van Leeuwen [SO], They reported a basket-shaped molecule functionalized with a catalytically active rhodium complex that catalyzed hydrogenation reactions according to the principles of enzymes. The system showed substrate selectivity, Michaelis Menten kinetics and rate enhancement by cooperative binding of substrate molecules. The hydroformylation of allyl catachol substrates resulted in a complex mixture of products. 

From the early 80s, the emergence of Supramolecular Chemistry as an important area of research has caused an explosion of interest in the chemistry of these basket-shaped molecules, which still continues. Not only the number of scientific publications dealing with the chemistry and host-guest properties of calixarenes and resorcinarenes is growing with geometrical progression, but also the number of patents follows the same trend, thus indicating that the interest in these compounds is more than academic. ... 

Figure 14. Stereoviews of the defensin dimer crystal structure [coordinates courtesy of D. Eisenberg (160)7. (A) Perspective that shows the basket shape of the molecule and the van der Waals surfaces of the charged side chains. In some cases, side-chain atom positions are not defined and have been placed in a low-energy conformation. (B) Perspective that shows the beta-sheets within each dimer and the subunit interaction.

Vogtle and Wambach recently for the first time described basket-shaped host molecules of the types 106a, b and 107 which apart from a 30-membered ring as the wall contain a floor-plate , which cannot dive through the 30-membered basket-... 

Dol. G.C. Kamer, P.C.J. Hartl. F. van Leeuwen. P.W.N.M. Nolte. R.J.M. Electrochemical and binding properties of a novel ferrocene-containing redox-active basket-shaped host molecule. J. Chem. Soc.. Dalton Trans. 1998. 2083-2090. 

Whereas Hunter did not obtain the catenane 16 directly from 14 and 17, but only after preparation of the intermediate 15, we independently succeeded in the same year in a one-step synthesis of a substituted representative of the same catenane type 16 (R = OCH3) starting from the simple components 17 and 18 [31], In connection with earlier syntheses of basket-shaped host molecules [32], we had applied the cyclohexylidene-substituted diamine 17 [33] instead of unsubstituted diphenylmethane, p-phenylene and naphthalene units in order to increase the solubility of macropolycyclic lactams of type 19. The OCH3-substituents introduced via 18 are intended to be cleaved to OH-groups after the cyclization process. This should be useful for further bridging and, in particular, for attaching the bottom of the basket (spacer in 20). 

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