Alcohol inclusion complexes

Table 10.6 compares the average size (DPn) and size distributions of six laboratory-purified amyloses and one commercial sample of potato amylose, which were determined by classic colorimetric and fluorescent-labeling techniques using 2-ami-nopyridine. The data by the two techniques are consistent and show that wheat and other cereal amyloses are smaller in size than those from root and tuber starches. The molar distribution technique indicated that wheat amylose contained two molecular species, compared with one for rice and com amyloses.209,210 Moreover, the molar size distributions for the cereal amyloses are much narrower than those of the tuber amyloses, and the cereal amyloses contain a preponderance of molecules of DPn < 1000 whereas the tuber amyloses contain 78-95% of molecules with DPn > 1000, and even 3-5% above DPn 10000. None of the amylose samples in Table 10.6 showed molecules with less than DPn 200, possibly because they had been purified as alcohol-inclusion complexes.209... 

ISOLATION AND CRYSTAL STRUCTURE OF ALCOHOL INCLUSION COMPLEXES... 

Inclusion phenomena can be used for the isolation of ethanol from its aqueous solution. We have been working towards this goal, and we have found some good host compounds which include ethanol. In order to design a good host molecule, it is also important to study the crystal structures of alcohol inclusion complexes. An X-ray crystal structural study of some alcohol inclusion complexes resulted in several interesting findings. Vie now review these. 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

The milder metal hydnde reagents are also used in stereoselective reductions Inclusion complexes of amine-borane reagent with cyclodexnins reduce ketones to opucally active alcohols, sometimes in modest enantiomeric excess [59] (equation 48). Diisobutylaluminum hydride modified by zmc bromide-MMA. A -tetra-methylethylenediamme (TMEDA) reduces a,a-difluoro-[i-hydroxy ketones to give predominantly erythro-2,2-difluoro-l,3-diols [60] (equation 49). The three isomers are formed on reduction with aluminum isopropoxide... 

For example, the same dimer complex which contains two molar equivalents of ethanol, underwent photoreaction to give a higher molecular weight polymer (M = 12 000). The formation of such inclusion complexes with the solvent is rather generally observed with similar types of dimers formed with alcohols and some other solvents and, consequently, this enhances photopolymerizability. Such complex formation with a solvent may be one of the promising techniques that can be used for diolehn compounds in order to obtain polymers with high molecular weights. 

Benzamido-cinnamic acid, 20, 38, 353 Benzofuran polymerization, 181 Benzoin condensation, 326 Benzomorphans, 37 Benzycinchoninium bromide, 334 Benzycinchoninium chloride, 334, 338 Bifiinctional catalysts, 328 Bifiinctional ketones, enantioselectivity, 66 BINAP allylation, 194 allylic alcohols, 46 axial chirality, 18 complex catalysts, 47 cyclic substrates, 115, 117 double hydrogenation, 72 Heck reaction, 191 hydrogen incorporation, 51 hydrogen shift, 100 hydrogenation, 18, 28, 57, 309 hydrosilylation, 126 inclusion complexes, oxides, 97 ligands, 19, 105 molecular structure, 50, 115 mono- and bis-complexes, 106 NMR spectra, 105 olefin isomerization, 96... 

Chiral crown ethers based on IB-crown-6 I Fig. 4> can form inclusion complexes with ammonium ions and proionated primary amines. Immobilization of these chiral crown ethers on a chromatographic support provides a chiral stationary phase which can resolve most primary amino acids, amines and amino alcohols. However, the stereogenic center must be in fairly close proximity in the primary aininc lor successful chiral separalion. Significantly, ihe chiral crown ether phase is unique in that ii is one of the few liquid chromatographic chiral stationary phases that does not require the presence of an aromatic ring to achieve chiral separations. 

Lipids in starchy foods may occur in the free as well as bound forms. The latter being either in the form of amylose inclusion complexes or linked via ionic or hydrogen bonding to the hydroxyl groups of the starch components. Free lipids are easily extractable at ambient temperatures, while use of nonalcoholic solvents for a prolonged period or disruption of the granular structure by acid hydrolysis (see Basic Protocol 4) may be required for the efficient extraction of bound lipids. While acid hydrolysis allows the release and quantitation of lipids, the procedure leads to destruction of the starch components therefore, the alcohol extraction system involving propanol and water would be most desirable in these cases. This system removes both nonpolar and polar lipids from samples. 

Keywords ketone, enantioselective reduction, BH3-ethylenediamin complex, inclusion complex, alcohol... 

A mixture of finely powdered inclusion complex of (-)-l with 2 was kept under N2 at room temperature for 24 h by occasional stirring. The reaction mixture was decomposed with water and extracted with ether. The ether solution was washed with dilute HC1, dried, and evaporated to give crude alcohols. Distillation of the crude alcohols in vacuo gave pure alcohols. 

The CD architecture is particularly fitting for excimer-based reporter sites. As long as the bucket is sufficiently large to accept two guests, monomers will cofacially organize within the interior of a CD to form excimer. Early spectroscopic studies revealed an enhanced excimer emission upon the addition of y-CD to solutions of naphthalene [361], a result that was subsequently observed for anthracene [362] and pyrene [363,364], Pyrene excimer formation has been examined in particular detail. Proper concentrations of pyrene and y-CD afford 2 1 or 2 2 excimer inclusion complexes. In both cases, pyrenes interact in a cofacial manner and excimer efficiently forms. Alcohol addition can disrupt the excimer by the preference to form a 1 1 1 complex of alcohol, pyrene, and CD. 

Although, at that time, the term supramolecular chemistry had not yet been coined, the practical potential for inclusion complexation for acetylene alcohol guests 1 and 2 was recognized back in 1968 [12], Spectroscopic studies showed that 1 and 2 formed molecular complexes with numerous hydrogen-bond donors and acceptors, i.e. ketones, aldehydes, esters, ethers, amides, amines nitriles, sulfoxides and sulfides. Additionally, 1 formed 1 1 complexes with several n-donors, such as derivatives of cyclohexene, phenylacetylene, benzene, toluene, etc. The complexation process investigated by IR spectrometry revealed the presence of OH absorption bands at lower frequencies than those for uncomplexed 1 and 2 [12], These data, followed by X-ray studies, confirmed that the formation of intermolecular hydrogen bonds is the driving force for the creation of complexes [13],... 

For example, when a suspension of powdered optically active host 3a was mixed with racemic 1-phenylethanol (4a) in a 1 1 molar ratio and stirred at room temperature for 6 h, a 2 1 inclusion complex was formed. When the filtered solid complex was heated in vacuo, it gave (—)-4a (95 % ee, 85 % yield). For the host compounds 3a-c, approximately the same ee (78-99.9 %) and high yield (75-93 %) could be achieved in the resolution of alcohols of the 4 and 5 series in water and hexane. It has been found that introducing... 

For example, when powdered host 27 was mixed with volatile rac-but-3-yn-2-ol (29) and left for 24 h, a 1 1 inclusion complex with (+1-29 was formed. The alcohol can be removed from the complex by heating in vacuo yielding 29 of 59 % ee and 77 % yield. A second complexation, followed by distillation in vacuo, gave (+)-29 of 99 % ee and 28 % yield. The best resolution of rac-29 reported to date was by enzymatic esterification, and gave chiral alcohol at 70 % ee and 31% yield [49], Host 27 could be used for optical resolution of rac-2-hexanol... 

In most cases, chiral alcohol and phenol derivatives are used as host compounds for the resolution. In these cases, guest molecules are accommodated in the complex by formation of hydrogen bond with the hydroxyl group of the host. Since the hydrogen bond is not very strong, the included guest compound can be recovered easily from the inclusion complex by distillation, recrystallization, chromatography or some other simple procedures. 

Tanaka, K., Honke, S., Urbanczyk-Lipkowska, Z., and Toda, F. New chiral hosts derived from dimeric tartaric acid efficient optical resolution of aliphatic alcohols by inclusion complexation, J. Org. Chem. 2000,(55,3171-3176. 

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