Isotope Chirality and Asymmetric Autocatalysis: A Possible Entry to Biological Chirality

Barabás, Béla; Caglioti, Luciano; Micskei, Károly; Zucchi, Claudia; Pályi, Gyula

doi:10.1007/s11084-008-9138-1

Cited by 45 publications

(37 citation statements)

References 52 publications

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“…The expectable enantiomeric excesses according to the Pars-Mills equation [40,48] (with 50% confidence, see also Supporting Materials 2) are as follows (Table 2). All supposed intermediates of the Soai reaction, however, contain two kinds (both C-bound and Zn-bound) i-Pr groups and more of these, than in the reagents shown in Figure 1.…”

Section: The Iso-propyl Group(s)mentioning

confidence: 89%

“…We calculated the expectable enantiomeric excesses (e.e.50%, %) with the Pars-Mills equation [40,48] (with 50% confidence, see also Supporting Materials 2) for sample sizes that could appear in usual micropreparative work (ranging from millimol to femtomol) ( Table 1). …”

Section: The Tert-butyl Groupmentioning

confidence: 99%

“…Utilizing the Pars-Mills equation [40,48] for calculation of the expected enantiomeric excesses (with 50% confidence, see also Supporting Materials 2), we obtain (Table 4). Complex case (isotopes of the oxygen atoms are considered).…”

Section: Zinc Isotopic Chirality?mentioning

confidence: 99%

“…We calculated with the Pars-Mills equation [40,48] (see also Supporting Materials 2) the expectable enantiomeric excesses for reasonable microchemical sample sizes (Table 5). Similar to the probability dates, the expectable e.e.…”

Section: Zinc Isotopic Chirality?mentioning

confidence: 99%

“…The sensitivity towards any chiral additive, or even a very small excess of the product results in the capacity of this reaction to produce very high enantiomeric excess from infinitesimally low one. The fundamental significance of this aspect of the Soai reaction in studies concerning the origin(s) of biological chirality has also been discussed [40].…”

Section: Introductionmentioning

confidence: 99%

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Natural Abundance Isotopic Chirality in the Reagents of the Soai Reaction

2016

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Isotopic chirality influences sensitively the enantiomeric outcome of the Soai asymmetric autocatalysis. Therefore magnitude and eventual effects of isotopic chirality caused by natural abundance isotopic substitution (H, C, O, Zn) in the reagents of the Soai reaction were analyzed by combinatorics and probability calculations. Expectable enantiomeric excesses were calculated by the Pars-Mills equation. It has been found that the chiral isotopic species formed by substitution in the otherwise achiral reagents provide enantiomeric excess (e.e.) levels that are higher than the sensitivity threshold of the Soai autocatalysis towards chiral induction. Consequently, possible chiral induction exerted by these e.e. values should be taken into account in considerations regarding the molecular events and the mechanism of the chiral induction in the Soai reaction.

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Section: The Iso-propyl Group(s)mentioning

confidence: 89%

Section: The Tert-butyl Groupmentioning

confidence: 99%

Section: Zinc Isotopic Chirality?mentioning

confidence: 99%

Section: Zinc Isotopic Chirality?mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Natural Abundance Isotopic Chirality in the Reagents of the Soai Reaction

2016

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Asymmetric Amplification and Autocatalysis

Soai

Kawasaki

Shibata

2010

Catalytic Asymmetric Synthesis

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INTRODUCTIONIn experimental studies on catalytic asymmetric synthesis, considerable attention has been paid to the interaction between chiral catalysts and the reactants to achieve high enantioselectivity. However, very little attention has been paid to the interaction between the enantiomers of a chiral catalyst when this catalyst is not enantiomerically pure.Examples of catalytic asymmetric synthesis have been reported in which the enantiomeric purity of the product is much higher than that of the chiral catalyst. A positive nonlinear effect (NLE), that is, asymmetric amplifi cation, is synthetically useful because a chiral catalyst with high ee is not needed to prepare a chiral product with high ee (Scheme 12.1 ).In asymmetric autocatalysis, the chiral catalyst P * and the product P * have the same structure; that is, the chiral product P * acts as a chiral catalyst P * for its own multiplication. Asymmetric autocatalysis differs from conventional catalytic asymmetric syntheses where the chiral catalyst C * and the product P * have different structures (Scheme 12.2 ).Highly enantioselective asymmetric autocatalysis has recently been reported. In such reactions, a trace amount of chiral molecule automultiplies without the assistance of another chiral molecule. Moreover, asymmetric autocatalysis with an amplifi cation of Catalytic Asymmetric Synthesis, Third Edition, Edited by Iwao Ojima

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Asymmetric Autocatalysis: Triggered by Chiral Isotopomer Arising from Oxygen Isotope Substitution

et al. 2011

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The substitution of the atoms in the enantiotopic moiety of an achiral molecule by their isotopes makes the present molecule chiral. [1, 2] Isotopically labeled compounds [3] have been used to elucidate structural information, [3b] mechanisms of organic reactions, [3c-e] and drug kinetics, [3f] however, asymmetric synthesis using the chirality generated by isotope substitution alone is difficult because of the very low enantiomeric excess (ee) displayed when using deuterated chiral compounds as a source of chirality. [4] Amplification effects of the helicity in the polyisocianates [5a] and supramolecular polymers [5b] that results from hydrogen isotopes (D/H) have been reported. And discrimination of hydrogen isotope chirality using spectroscopic methods [6] and HPLC analyses with a chiral stationary phase [7] have been reported.Recently, we have reported asymmetric autocatalysis with amplification of ee values [8][9][10][11] that was triggered by chiral compounds resulting from hydrogen (D/H) [12] and carbon isotope ( 13 C/ 12 C) [13] substitutions. Meanwhile, the syntheses of chiral compounds resulting from oxygen isotope substitutions [14] and oxygen kinetic isotope effects (KIEs) [15] have been reported. However, to the best of our knowledge, there have been no reports of asymmetric synthesis or induction utilizing chiral compounds resulting from oxygen isotope substitution. Therefore, asymmetric autocatalysis initiated by chiral compounds arising from 18 O/ 16 O substitution is challenging.We selected a meso compound as the oxygen isotope enantiomer (Scheme 1). Achiral meso hydrobenzoin forms chiral oxygen isotopomers 1 after 18 O labeling of the hydroxy group in an enantioselective manner. These diols should be chiral only as a result of the oxygen isotope ( 18 O/ 16 O) substitution. The enantiomer whose 18 O atom is bound to the S-configured carbon center is described as [ 18 O](S)-1, while the opposite is described as [ 18 O](R)-1.Herein we report the first asymmetric induction by chiral compounds arising from oxygen isotope substitution in conjunction with asymmetric autocatalysis (Scheme 1). The chiral compound created by oxygen isotope substitution serves as the chiral trigger of asymmetric autocatalysis to afford alkanol 3 with high ee values. The relationship between the absolute configurations of the chiral 18 O-labeled hydrobenzoin ([ 18 O]1) and the product alkanol 3 is reproducible.The enantiomers of [ 18 O]1 were synthesized from chiral trans-stilbene oxide (4), which was obtained by resolution of its racemate by HPLC methods using a chiral stationary phase. The enantiomers of oxide 4 had ee values greater than 99.5 % and were submitted to the epoxide-opening reaction using [ 18 O]H 2 O under basic reaction conditions (Figure 1 A). By using 2-methoxyethanol as a cosolvent, the hydrolysis of the epoxide by [ 18 O]H 2 O proceeded stereoselectively to form the chiral [ 18 O]1 predominantly. The enantioenrichment of the synthesized compound 1 was confirmed by 13 C NMR spectroscopic analysis...

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Isotope Chirality and Asymmetric Autocatalysis: A Possible Entry to Biological Chirality

Cited by 45 publications

References 52 publications

Natural Abundance Isotopic Chirality in the Reagents of the Soai Reaction

Natural Abundance Isotopic Chirality in the Reagents of the Soai Reaction

Asymmetric Amplification and Autocatalysis

Asymmetric Autocatalysis: Triggered by Chiral Isotopomer Arising from Oxygen Isotope Substitution

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