Privileged Chiral Catalysts

Yoon, Tehshik P.; Jacobsen, Eric N.

doi:10.1126/science.1083622

Cited by 1,328 publications

(904 citation statements)

References 21 publications

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“…S ince the first demonstration of the handedness of tartaric acid molecules by Pasteur 1 , resolution of enantiomers and dissymmetric induction in synthesis have been important from the perspectives of both science and technology [2][3][4][5] . In recent years, much effort has been expended on researching methods of fabricating nanoscale chiral surfaces, in many cases with the goal of improving enantioselectivity in asymmetric induction 6 , high-performance liquid chromatography 7,8 and high-sensitivity chirality detection 9,10 .…”

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confidence: 99%

Diastereomeric liquid crystal domains at the mesoscale

et al. 2015

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In many technologies used to achieve separation of enantiomers, chiral selectors are designed to display differential affinity for the two enantiomers of a chiral compound. Such complexes are diastereomeric, differing in structure and free energy for the two enantiomers and enabling chiral discrimination. Here we present evidence for strong diastereomeric interaction effects at the mesoscale, manifested in chiral liquid crystal guest materials confined in a chiral, nanoporous network of semi-crystalline helical nanofilaments. The nanoporous host is itself an assembly of achiral, bent-core liquid crystal molecules that phase-separate into a conglomerate of 100 micron-scale, helical nanofilament domains that differ in structure only in the handedness of their homogeneous chirality. With the inclusion of a homochiral guest liquid crystal, these enantiomeric domains become diastereomeric, exhibiting unexpected and markedly different mesoscale structures and orientation transitions producing optical effects in which chirality has a dominant role.

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confidence: 99%

Diastereomeric liquid crystal domains at the mesoscale

et al. 2015

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“…Enantioselectivity in these processes is expected to result in ecotoxicological effects that cannot be predicted from our existing knowledge and must be considered in future risk assessment and regulatory decisions. chiral contaminants ͉ chirality ͉ enantiomers ͉ chiral pesticides ͉ chiral selectivity T he significance of molecular chirality is widely recognized in life sciences (1,2). A lesser-known fact is that many modern pesticides also contain chiral structures and thus consist of enantiomers (3,4).…”

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confidence: 99%

Enantioselectivity in environmental safety of current chiral insecticides

Liu

Gan

Schlenk

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

452

395

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Chiral pesticides currently constitute about 25% of all pesticides used, and this ratio is increasing as more complex structures are introduced. Chirality occurs widely in synthetic pyrethroids and organophosphates, which are the mainstay of modern insecticides. Despite the great public concerns associated with the use of insecticides, the environmental significance of chirality in currently used insecticides is poorly understood. In this study, we resolved enantiomers of a number of synthetic pyrethroid and organophosphate insecticides on chiral selective columns and evaluated the occurrence of enantioselectivity in aquatic toxicity and biodegradation. Dramatic differences between enantiomers were observed in their acute toxicity to the freshwater invertebrates Ceriodaphnia dubia and Daphnia magna, suggesting that the aquatic toxicity is primarily attributable to a specific enantiomer in the racemate. In field sediments, the (؊) enantiomer of cis-bifenthrin or cispermethrin was preferentially degraded, resulting in relative enrichment of the (؉) enantiomer. Enantioselective degradation was also observed during incubation of sediments under laboratory conditions. Enantioselectivity in these processes is expected to result in ecotoxicological effects that cannot be predicted from our existing knowledge and must be considered in future risk assessment and regulatory decisions. chiral contaminants ͉ chirality ͉ enantiomers ͉ chiral pesticides ͉ chiral selectivity T he significance of molecular chirality is widely recognized in life sciences (1, 2). A lesser-known fact is that many modern pesticides also contain chiral structures and thus consist of enantiomers (3, 4). About 25% of currently used pesticides are chiral, and this ratio is increasing as compounds with more complex structures are introduced into use (3). Enantiomers of the same compound have identical physical-chemical properties and thus appear as a single compound in standard analysis. For economic reasons, chiral pesticides are primarily used as mixtures of enantiomers, or racemates. However, enantiomers are known to selectively interact with biological systems that are usually enantioselective and may behave as drastically different compounds. The role of enantioselectivity in environmental safety is poorly understood for pesticides, and the knowledge gap is reflected in that the great majority of chiral pesticides are used and regulated as if they were achiral, that is, single compounds.Studies on chiral pesticides started to appear in the early 1990s (4,(5)(6)(7)(8)(9)(10)(11)(12). Studies so far show that microbial degradation of chiral pesticides is commonly enantioselective. As one enantiomer is preferentially degraded, the enantiomer ratio (ER), defined as the ratio of (ϩ) enantiomers to (Ϫ) enantiomers, increasingly deviates from the original value (typically 1.0) (8, 9). Enantioselectivity was found to result in changes of ER in ␣-HCH along the polar bear food chain, causing ER to increase from Ϸ1.0 in cod to 2.3 in liver samples of polar be...

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“…That is to say, chemists often develop not an optimal but a satisfactory synthetic procedure, catalyst or drug molecule. We believe that an earmark of all these situations is the recognition of so-called privileged structures in drug 40 and catalysis 41 developments. The privileged structures are not necessarily the optimal structures, but the satisfactory structures that are synthetically easily available.…”

Section: Can We Reach the Maximum Synthetic Output?mentioning

confidence: 99%

Anthropogenic reaction parameters – the missing link between chemical intuition and the available chemical space

2014

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How do skilled synthetic chemists develop such a good intuitive expertise? Why can we only access such a small amount of the available chemical space -both in terms of the reactions used and the chemical scaffolds we make? We argue here that these seemingly unrelated questions have a common root and are strongly interdependent. We performed a comprehensive analysis of organic reaction parameters dating back to 1771 and discovered that there are several anthropogenic factors that limit the reaction parameters and thus the scope of synthetic chemistry. Nevertheless, many of the anthropogenic limitations such as the narrow parameter space and the opportunity of the rapid and clear feedback on the progress of reactions appear to be crucial for the acquisition of valid and reliable chemical intuition. In parallel, however, all of these same factors represent limitations for the exploration of available chemistry space and we argue that these are thus at least partly responsible for limited access to new chemistries. We advocate, therefore, that the present anthropogenic boundaries can be expanded by a more conscious exploration of "off-road" chemistry that would also extend the intuitive knowledge of trained chemists.

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Privileged Chiral Catalysts

Cited by 1,328 publications

References 21 publications

Diastereomeric liquid crystal domains at the mesoscale

Diastereomeric liquid crystal domains at the mesoscale

Enantioselectivity in environmental safety of current chiral insecticides

Anthropogenic reaction parameters – the missing link between chemical intuition and the available chemical space

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