Host, chiral, inclusion complexation

Enantioselective self-assembling of amino acids 209 Host-guest inclusion complexes 213 Reactivity of chiral ion-dipole complexes 233... 

Chiral recognition, see also Host-guest inclusion complexes... 

Host-guest inclusion complexes, 262—263 antibiotic hosts, 231—233 cahxarene hosts, 228—231 chiral crown ether hosts, 213—218 cyclic oligosaccharide hosts, 218—222 cyclodextrin host selectivities, 223/ host molecular size, 221 hnear ohgosaccharide hosts, 222—228 ir- TT stacking interactions, 217 proteic hosts, 231 Human 15-hpoxygenase, 52/... 

Tanaka, K., Moriyama, A., and Toda, F. (1997) Novel Chiral Recognition in Host-Guest Inclusion Complexes Depending on Their Molar Ratios Efficient Resolution of 2,2 -Dihydroxy-1,1 -binaphthyl Derivatives and CD Spectral Study of Inclusion Complex Crystals, J. Org. Chem., 62, 1192-1193. 

HOST-GUEST INCLUSION COMPLEXES Chiral crown ether hosts... 

An inclusion compound is composed of two or more distinct molecules held together by noncovalent forces in a definable structural relationship. Chiral inclusion complexes have been used by the groups of Lahav, Leisorowitz, and Toda to carry out asymmetric photoreactions [208-245]. The chirality of the host... 

A different non-classical approach to the resolution of sulphoxides was reported by Mikolajczyk and Drabowicz269-281. It is based on the fact that sulphinyl compounds very easily form inclusion complexes with /1-cyclodextrin. Since /1-cyclodextrin as the host molecule is chiral, its inclusion complexes with racemic guest substances used in an excess are mixtures of diastereoisomers that should be formed in unequal amounts. In this way a series of alkyl phenyl, alkyl p-tolyl and alkyl benzyl sulphoxides has been resolved. However, the optical purities of the partially resolved sulphoxides do not exceed 22% after... 

A regio- and stereoselective Beckmann rearrangement utilized diastereose-lective host guest interactions of the inclusion complexes 225 and 228 in a solid state reaction. Initially, a 1 1 mixture of the chiral host 223 and the racemic oximes 224 and 227, respectively, was treated with ultra sound in the solid state to induce the optical resolution. Then H2SO4 was added to start the Beckmann rearrangement, the corresponding c-caprolactams 226 and 229 were isolated in 68 % and 64 % yields and ee of about 80 % and 69 % (determined by HPLC analysis on chiracel OC) (Scheme 43) [46]. 

Some solid-solid reactions were shown to proceed efficiently in a water suspension medium in Sect. 2.1. When this reaction, which gives a racemic product, is combined with an enantioselective inclusion complexation with a chiral host in a water suspension medium, a unique one-pot preparative method of optically active product in a water medium can be constructed. Some such successful examples are described. 

An enantioselective Michael addition reaction was also accomplished in an inclusion complex with a chiral host compound. Treatment of a 1 1 complex of 10c and 66b with 2-mercaptopyridine (137) in the solid state gave (+)-138 of 80% ee in 51% yield. By a similar method, 3-methyl-3-buten-2-one (139) gave (+)-140 of 49% ee in 76% yield [30]. 

It is not easy to control the steric course of photoreactions in solution. Since molelcules are ordered regularly in a crystal, it is rather easy to control the reaction by carrying out the photoreaction in a crystal. However, molecules are not always arranged at an appropriate position for efficient and stereoselective reaction in their crystals. In these cases inclusion chemistry is a useful technique, as it can be employed to position molecules appropriately in the host-guest structure. Chiral host compounds are especially useful in placing prochiral and achiral molecules in suitable positions to yield the desired product upon photoirradiation. Some controls of the steric course of intramolecular and intermolelcular photoreactions in inclusion complexes with a host compound are described. 

Enantiocontrol of the photocyclization of Ar-methyl-AT-phenyl-3-amino-2-cyclohexen-l-one (151a,b) to the corresponding AT-methylhexahydro-4-car-bazolones (153a,b) via the dipolar ionic intermediate (152a,b) (Scheme 22) was also accomplished by photoirradiation of 1 1 inclusion complexes of 151 a,b with the chiral hosts lOa-c. Of the complexes prepared, 10a-151a, 10a-151b,... 

Control of Enantioselective Photoreactions in Inclusion Complexes with Chiral Host Compounds... 

There are several cases that have addressed molecular recognition of chiral drugs by modified CDs127 as well as inclusion complexes of cationic, anionic and neutral organic compounds128 in order to understand the role of hydrophobic and electrostatic interactions between the functional groups on host and guest. 

Tanaka K, Mochizuki E, Yasui N, Kai Y, Miyahara I, Hirotsu K, Toda F (2000) Single-crystal-to-single-crystal enantioselective [2-1-2] photodimerization of coumarin, thiocoumarin and cyclohex-2-enone in the inclusion complexes with chiral host compounds. Tetrahedron 56 6853-6865... 

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