Chirality, effect

Breit B (2007) Recent Advances in Alkene Hydroformylation. 279 139-172 Brizard A, Oda R, Hue I (2005) Chirality Effects in Self-assembled Fibrillar Networks. 256 167-218... 

Chiral effects in rydberg electron-bound complexes 194... 

CHIRAL EFFECTS IN RYDBERG ELECTRON-BOUND COMPLEXES... 

More comprehensive CIMS investigations on tartrate systems indicate that the dimer chirality effects disappear when the ester functions of tartrates is replaced by H or an alkyl function, e.g., methyl or cyclohexyl. A similar effect is observed when the proton in the proton-bound dimers is replaced by lithium or ammonium ion. These observations are attributed to a dramatic change in the basket-type... 

The same CIMS approach has been used for investigating the self-recognition processes in proton-bound tartrate trimers. The trimer chirality effect is consistent with the heterochiral trimers as more stable than the homochiral ones. The reverse is true when the proton in the proton-bound trimers is replaced by hydronium, ammonium ion, or primary aminium ions. " This changeover is... 

Table 6 Chirality effects in the dimerization of homologous tartrate esters... 

The dimer chirality effect, Aihomo/ hetero = 0.33 corresponds... 

Because of their asymmetry, CDs exhibit chiral effects towards chiral molecules under FAB" and MALDl conditions. The main ambiguity of these studies remains regarding the environment in which chiral recognition occurs, whether in the bulk matrix, in the selvedge vaporization region, or in the gas phase. Besides, neither MALDI nor EAB ensure attainment of purely kinetic or equilibrium conditions so as that quantitative interpretation of the MS patterns in terms of relative stabihty of diastereomeric host/guest intermediates or transition stmctures... 

Probably of more significance are chiral effects in metabolism, which can be divided into... 

As an example of the first type of chiral effect, metabolism of the drug bufuralol may be considered. Hydroxy la tion in the V position only occurs with the (+) isomer, whereas for hydroxylation in positions 4 and 6, the (—) isomer is the preferred substrate (Fig. 5.3). Glucuronidation of the side chain hydroxyl group is specific for the (+) isomer. A further complication in human subjects is that the 1-hydroxylation is under genetic control, being dependent on the debrisoquine hydroxylator status (see below). The selectivity for the isomers for the hydroxylations is virtually abolished in poor metabolizers. 

An example of the second type of chiral effect in metabolism is afforded by benzofa]-pyrene, also discussed in more detail in chapter 7. This carcinogenic polycyclic hydrocarbon is metabolized stereos elec lively by a particular cytochrome P-450 isozyme, CYP1A1, to the (+)-7R,8S oxide (chap. 7, Fig. 5.2), which in turn is metabolized by epoxide hydrolase to the (—)-7R,8S dihydrodiol. This metabolite is further metabolized to (- -)-benzo[aIpyrene, 7R,8S dihydrodiol, 9S,10R epoxide in which the hydroxyl group and epoxide are trans and which is more mutagenic than other enantiomers. The (—)-7R,8S dihydrodiol of benzo[aIpyrene is 10 times more tumorigenic than the (+)-7R,8S enantiomer. It was reported that in this case the configuration was more important for tumorigenicity than the chemical reactivity. 

Helical polymers, formed as they usually are from chiral monomers, are themselves chiral. If an attempt is made to stack them in a regular parallel array, there will be a tendency for successive layers to be gradually twisted round with respect to the original layer. It is possible that the chiral effect is responsible for the fact that the polyglutamates tend to deposit at an angle of 35° to the dipping direction. A study of a racemic mixture of one of these materials would clarify this point. 

The last two dendrimer types are less well known, because in the case of D the chirality is low or in the case of E the interpretation of chiral effects probably proves difficult (see Section 4.2.7). 

Drak, J., and Crothers, D. M. (1991). Helical repeat and chirality effects on DNA gel electrophoretic mobility. Proc. Natl. Acad. Sri. USA 88, 3074—3078. 

A pronounced chirality effect on the chemical reactivity of ylid complexes is to be expected from propeller-type ligands with a C2 rotation axis. In a first attempt to synthesize pertinent examples, a spirobicyclic ylide 1 was designed (11) and converted into a novel lithio-derivative 2, which on reaction with metal halides yields multi-spiro complexes of unusual geometries ... 

The final aim of this work is to encourage the experimental study of these complexes and understand the importance of the chiral effect of the different monomers within the final clusters as has been shown in the experimental study of hydrazine and lactate clusters. Another report on the different motifs of hydrogen peroxide clusters has also been published that shows similar energetic trends to the ones found in our work, but without considering their implications in the chiral recognition processes [119]. 

Cheng Y, Cui W, Chen Q et al (2011) The molecular mechanism studies of chirality effect of PHA-739358 on Aurora kinase A by molecular dynamics simulation and free energy calculations. J Comput Aided Mol Des 25(2) 171-180... 

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