Chiral autocatalysis: where stereochemistry meets the origin of life

Авалос, M.; Babiano, Reyes; Cintas, Pedro; Jiménez, José L.; Palacios, Juan C.

doi:10.1039/a908300f

Cited by 173 publications

(65 citation statements)

References 53 publications

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“…However, none of those systems involve prochiral molecules, meaning that the origin of the first imbalance in asymmetric centers is not at issue in these cases; when we examine von Kiedrowski's (37,38) autocatalytic system based on DNA hexamers, for example, we know we are already firmly committed and residing in the camp of the L-amino acids and the D-sugars. We might agree with Cintas and coworkers' (44) view that the Soai system represents a ''triumph of reductionism'' in helping us to understand the chemical origin of life in molecular terms, but we also accept his statement that there remains a ''large gap between molecular chirality and molecular evolution.'' Thus, further studies ought to be aimed at trying to provide information that might help close this gap.…”

Section: Discussionsupporting

confidence: 69%

Asymmetric autocatalysis and its implications for the origin of homochirality

Blackmond

2004

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

301

127

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An autocatalytic reaction in which the reaction product serves as a catalyst to produce more of itself and to suppress production of its enantiomer serves as a mechanistic model for the evolution of homochirality. The Soai reaction provided experimental confirmation of this concept, nearly 50 years after it was first proposed. This Perspective offers a rationalization of the Soai autocatalytic reaction; accounting for enantiomeric excess and rate observations, that is both simple as well as gratifying in its implications for the chemical origin of life.

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Section: Discussionsupporting

confidence: 69%

Asymmetric autocatalysis and its implications for the origin of homochirality

Blackmond

2004

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

301

127

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“…However, modern theoretical studies [11][12][13][14][15][16][17][18][19][20][21][22][23]26,28,30,31,33,[36][37][38][39][40][41]43,44,46] have claimed that an image and its mirror molecule are no longer enantiomers due to an energy inequality induced by the existence of PV-WNC. Due to a parity-violating energy shift (PVES) of the electronic binding energy with a positive value, +E PV , for the image molecule and a PVES with a negative value, -E PV , for the mirror image molecule, or vice versa, PVES makes the pair become a diastereomer, exhibiting subtle differences in physical properties and chemical processes.…”

Section: Introductionmentioning

confidence: 99%

“…In the molecules containing heavy elements, PVED may increase up to ~10 -14 eV due to the heavy element effect [43], yet it still remains undetectable. Thus far, several amplification models, including polymerization and crystallization [5], molecules with heavier atoms [20], tunneling and oscillating between left and right in a double well [11], non-equilibrium autocatalytic chemical reactions [15,38], and second-order phase transition systems [26], have been proposed. Several experimental results testing the MPV hypothesis have been reported so far.…”

Section: Introductionmentioning

confidence: 99%

Mirror Symmetry Breaking in Helical Polysilanes: Preference between Left and Right of Chemical and Physical Origin

Fujiki

2010

Symmetry

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Abstract:From elemental particles to human beings, matter is dissymmetric with respect to mirror symmetry. In 1860, Pasteur conjectured that biomolecular handednesshomochirality-may originate from certain inherent dissymmetric forces existing in the universe. Kipping, a pioneer of organosilicon chemistry, was interested in the handedness of sodium chlorate during his early research life. Since Kipping first synthesized several Si-Si bonded oligomers bearing phenyl groups, Si-Si bonded high polymers carrying various organic groups-polysilanes-can be prepared by sodium-mediated condensation of the corresponding organodichlorosilanes. Among these polysilanes, optically active helical polysilanes with enantiomeric pairs of organic side groups may be used for testing the mirror symmetry-breaking hypothesis by weak neutral current (WNC) origin in the realm of chemistry and material science. Several theoretical studies have predicted that WNC-existing chiral molecules with stereogenic centers and/or stereogenic bonds allow for distinguishing between image and mirror image molecules. Based on several amplification mechanisms, theorists claimed that minute differences, though still very subtle, may be detectable by precise spectroscopic and physicochemical measurements if proper chiral molecular pairs were employed. The present paper reports comprehensively an inequality between six pairs of helical polysilane high polymers, presumably, detectable by (chir)optical and achiral 29 Si-/ 13 C-NMR spectra, and viscometric measurements.

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“…22 However, it seems to be difficult to demonstrate their prediction because the chirally autocatalytic reaction is presently a rare phenomenon. 23,24 Our strategy to obtain large MFE in asymmetric reactions is that the magnetic-field-dependent ISC process of radical pairs or biradicals is incorporated into asymmetric photolysis with CPL. While CPL is the only chiral source, the magnetic field has no chirally asymmetric influence.…”

mentioning

confidence: 99%

Asymmetric Photolysis of 2-Phenylcycloalkanones with Circularly Polarized Light: A Kinetic Model for Magnetic Field Effects

Kohtani¹,

Sugiyama²,

Fujiwara³

et al. 2002

Bulletin of the Chemical Society of Japan

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Magnetic field effects (MFE) on asymmetric photolysis involving a biradical intermediate have been investigated on a kinetic model where an intersystem crossing (ISC) of the intermediate is taken into account. Changes in the enantiomeric excesses (ee) of chiral substances with circularly polarized light (CPL) irradiation have been simulated, and the necessary conditions for observing the MFE were obtained. The asymmetric photolysis of racemic 2-phenylcycloalkanones (2-PCAs) with CPL has been carried out in both the presence and absence of a magnetic field. Since the anisotropy g factors of 2-PCAs are considerably large, the CPL-induced ee are achieved to a few percent after 90% decomposition though the MFE are not observed. The photolysis mechanism of 2-PCAs in an air-saturated solution has been also clarified. Triplet acyl–benzyl biradicals, formed via photochemical α-cleavage of 2-PCAs, react with O2 dissolved in the solution and result in the formation of acetophenone and alkenoic acids. The bimolecular reactions are diffusion-controlled and the rates are comparable to those of ISC to the singlet biradicals for all 2-PCAs. The recombination yields of the biradicals are sufficiently large. However, the biradical ISC rate shows little magnetic field dependence, which explains the absence of the MFE in this asymmetric photolysis.

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Chiral autocatalysis: where stereochemistry meets the origin of life

Cited by 173 publications

References 53 publications

Asymmetric autocatalysis and its implications for the origin of homochirality

Asymmetric autocatalysis and its implications for the origin of homochirality

Mirror Symmetry Breaking in Helical Polysilanes: Preference between Left and Right of Chemical and Physical Origin

Asymmetric Photolysis of 2-Phenylcycloalkanones with Circularly Polarized Light: A Kinetic Model for Magnetic Field Effects

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