Optical enrichment of a racemic chiral crystal by X-ray irradiation

Osano, Yasuko T.; Uchida, Akira; Ohashi, Yuji

doi:10.1038/352510a0

Cited by 40 publications

(12 citation statements)

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“…The R : S ratio in a crystal changed from 50 : 50 to 75 : 25. This result indicates that a partial racemicto-chiral transformation or optical enrichment occurred in a crystal only by photoirradiation [55][56][57]. This is the first direct observation of racemic-to-chiral transformation.…”

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confidence: 63%

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Ohashi¹

2013

Crystallography Reviews

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The various alkyl groups bonded to the cobalt atom in (alkyl)(base)cobaloxime complex crystals are isomerized on exposure to visible light without degradation of the single crystal form. The solid-state reactions keeping the single crystal form were called crystalline-state reactions and the reaction mechanisms were explained with the concept of reaction cavity for the alkyl group. Changing the axial base ligands, a variety of crystalline-state reactions were examined not only by X-rays but also by neutron diffraction. The various reaction paths were made clear from the structures of initial, intermediate and final stages of the reactions. Moreover, the reaction rate was proved to have a positive relation with the volume of reaction cavity in each reaction. Not only various isomerizations but also unusual racemic-to-chiral transformations and a chirality inversion were also observed and the mechanisms were clearly explained and the shape of the reaction cavity made clear the mechanism. Two promising methods to observe the photoreaction with retention of the single crystal form, mixed crystal formation and bulky group insertion, are proposed and several successful results are shown.

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confidence: 63%

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Ohashi¹

2013

Crystallography Reviews

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“…Ohashi reported the X‐ray irradiation of the enantiomorphous crystal of a racemic cobalt complex to give enantioenriched compound. Because the two enantiomers were not symmetry related in the crystal lattice, racemization occurred for only one enantiomer and the other remained stable 37. Lahav reported that a racemic diene with a sec ‐butyl group crystallized in chiral space group P 1, which consists of a disordered solid‐solution of the two enantiomers.…”

Section: Asymmetric Autocatalysis Induced By a Chiral Crystal Compmentioning

confidence: 99%

Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

Kawasaki

Soai

2012

Israel Journal of Chemistry

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investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved.Keywords: asymmetric autocatalysis · amplification of chirality · origin of chirality · homochirality · chiral crystal · isotope chirality[a] T.

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“…The pioneering study of such class of ''absolute'' asymmetric transformations, by Penzien and Schmidt [35], was the gas-solid asymmetric bromination of the nonchiral p, p -dimethyl-chalcone, which crystallizes in an enantiomorphous crystal. Following this study, the details of over 20 such photoinitiated and thermally initiated reactions have been reported [36][37][38][39][40][41][42].…”

Section: ''Absolute'' Asymmetric Polymerization In 3-d Crystalsmentioning

confidence: 99%

“Absolute” Asymmetric Polymerization within Crystalline Architectures: Relevance to the Origin of Homochirality

Weissbuch

Lahav

2012

Materials Science and Technology

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The emergence of the homochiral proteins and nucleic acids, composed from residues of L-amino acids and D-sugars respectively, from the achiral prebiotic world still provides an unsolved conundrum in the field of the origin of life. This mist results from the fundamental symmetry rules as defined, at the end of the nineteenth century, by the Curie principle [1], which states that, '' . . . a physical event cannot have a symmetry lower than that of the event that caused it.''There are two classes of asymmetric transformation, which are in keeping with this symmetry rule. In the first class, chiral reactants are converted, via chemical reactions, into chiral products; in the second class, ''mirror-symmetry'' can be broken spontaneously in either a single or a small number of chemical reactions. In a large number of related independent events, however, the system will preserve its initial nonchiral symmetry. Such class of stochastic asymmetric transformations might have been relevant to chiro-biogenesis, provided the scenario can be accepted that life started in a small number of locations, and that the handedness generated by chance has been amplified and propagated during a competition with heterochiral architectures, such that one of the homochiral architectures has tripped and the other has won the rivalry [2][3][4][5].In this chapter, the second class of stochastic asymmetric synthesis of polymers -referred to as ''absolute'' asymmetric synthesis -and which has been materialized in laboratory experiments, is described. Several successful systems of ''mirror-symmetry breaking'' have been shown to comprise the following steps: spontaneous self-assembly of molecules into crystalline-like supramolecular architectures that create a local homochiral molecular environment exerting asymmetric induction in the ensuing propagation of the polymerization reaction. Farina [6] coined the term ''through-space'' asymmetric transformations in order to distinguish them from the common ''through-bond'' reactions.Here, attention is confined especially to the asymmetric transformations of achiral monomers within crystalline or quasi-crystalline architectures. In particular, the early studies of asymmetric polymerizations performed within enantiomorphous

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Optical enrichment of a racemic chiral crystal by X-ray irradiation

Cited by 40 publications

References 4 publications

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

“Absolute” Asymmetric Polymerization within Crystalline Architectures: Relevance to the Origin of Homochirality

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