Chiral resolution of l- and d-alanine and a racemic macrocyclic nickel(II) complex: synthesis and crystal structures
01 Mar 2014-Transition Metal Chemistry (Springer International Publishing)-Vol. 39, Iss: 2, pp 135-140
TL;DR: In this paper, the reaction of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two sixcoordinate enantiomers formulated as Ni(RR-L)(l-Ala) and ClO4·2CH3CN, respectively.
Abstract: The reactions of a racemic four-coordinate Ni(II) complex [Ni(rac-L)](ClO4)2 with l- and d-alanine in acetonitrile/water gave two six-coordinate enantiomers formulated as [Ni(RR-L)(l-Ala)](ClO4)·2CH3CN (1) and [Ni(SS-L)(d-Ala)](ClO4) (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane, Ala− = alanine anion), respectively. Evaporation from the remaining solutions gave two four-coordinate enantiomers characterized as [Ni(SS-L)](ClO4)2 (S-3) and [Ni(RR-L)](ClO4)2 (R-3), respectively. Single-crystal X-ray diffraction analyses of complexes 1 and 2 revealed that the Ni(II) atom has a distorted octahedral coordination geometry, being coordinated by four nitrogen atoms of L in a folded configuration, plus one carboxylate oxygen atom and one nitrogen atom of l- or d-Ala− in mutually cis-positions. Complexes 1 and 2 are supramolecular stereoisomers, constructed via hydrogen bonding between [Ni(RR-L)(l-Ala)]+ or [Ni(SS-L)(d-Ala)]+ monomers to form 1D hydrogen-bonded zigzag chains. The homochiral natures of complexes 1 and 2 have been confirmed by CD spectroscopy.
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01 Jan 2017
TL;DR: In this article, 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral neighbors with 6-amino-6-deoxy-β-cyclodesyntextrin (am-β -CD) in water at 298 K.
Abstract: We report new 3D fragment descriptors to model parameters and properties of stereoisomeric molecules and conformers. New 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral guests with 6-amino-6-deoxy-β-cyclodextrin (am-β-CD) in water at 298 K. The in-house software, mfSpace (Molecular Fragments Space), was used for QSPR modeling, generation and coding of the 3D fragment descriptors. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method. We used ensemble modeling techniques which include the generation of many individual models, the selection of the most relevant ones and followed by their joint application to test compounds, i.e., applying a consensus model for average predictions. The models based on 2D and 3D fragment descriptors provide the best predictions in external fivefold cross-validation: root mean squared error RMSE = 1.1 kJ/mol and determination coefficient $$R_{{det}}^{2}$$Rdet2 = 0.918 (β-CD), RMSE = 0.89 kJ/mol and $$R_{{det}}^{2}$$Rdet2 = 0.910 (am-β-CD).
5 citations
Cites background from "Chiral resolution of l- and d-alani..."
...l-alanine [55] has the fragment C–C–C=O_abC, when d-alanine [55] possesses the fragment C–C–C=O_abA, and cis- and trans-β-butylene have the fragments C–C=C–C_bbA and C–C=C–C_bbD, respectively....
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TL;DR: In this paper, 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral neighbors with 6-amino-6-deoxy-β-cyclodesyntextrin (am-β -CD) in water at 298 K. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method
Abstract: We report new 3D fragment descriptors to model parameters and properties of stereoisomeric molecules and conformers. New 3D fragment descriptors have been applied to discriminate between stereoisomers in predictive QSPR modeling of the standard free energy (∆G°) for the 1:1 inclusion complexation of 76 chiral guests with β-cyclodextrin (β-CD) and 40 chiral guests with 6-amino-6-deoxy-β-cyclodextrin (am-β-CD) in water at 298 K. The in-house software, mfSpace (Molecular Fragments Space), was used for QSPR modeling, generation and coding of the 3D fragment descriptors. The program implements the Singular Value Decomposition for Multiple Linear Regression analysis as machine learning method. We used ensemble modeling techniques which include the generation of many individual models, the selection of the most relevant ones and followed by their joint application to test compounds, i.e., applying a consensus model for average predictions. The models based on 2D and 3D fragment descriptors provide the best predictions in external fivefold cross-validation: root mean squared error RMSE = 1.1 kJ/mol and determination coefficient $$R_{{det}}^{2}$$
= 0.918 (β-CD), RMSE = 0.89 kJ/mol and $$R_{{det}}^{2}$$
= 0.910 (am-β-CD).
4 citations
TL;DR: In this paper, three enantiomeric pairs of novel homochiral coordination compounds (HCCs) with the formula {[Zn(D-hpg)(4,4′-bipy)(H2O)] · (NO3)}n 1-L, {Zn (Lhpg)2(4, 4′-Bipy)
2 citations
TL;DR: In this article, the macrocyclic nickel(II) complexes can easily take up and fix atmospheric CO2 at room temperature, and the chiral nature of complex 2 has been confirmed by CD spectroscopy.
Abstract: Two dinuclear carbonato-bridged nickel(II) complexes formulated as [Ni(rac-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (1) and [Ni(SS-L)]2(µ-CO3)(H2O)(im)4(ClO4)2 (2) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, im = imidazole) were isolated from the reactions of [Ni(rac-L)](ClO4)2 and [Ni(SS-L)](ClO4)2 with imidazole in the air, respectively, and a hydrocarbonato-coordinated nickel(II) complex formulated as [Ni(rac-L)](HCO3)(ClO4) (3) was reacted with obtained when [Ni(rac-L)](ClO4)2 reacted with l-cysteine under weakly basic conditions in the air. We found that the macrocyclic nickel(II) complexes can easily take up and fix atmospheric CO2 at room temperature. Single-crystal X-ray diffraction analyses revealed of all three complexes that the central Ni(II) atoms all have a six-coordinated distorted octahedral coordination geometry, and the carbonate anion bridges two Ni(II) atoms in a tridentate fashion to form dimers in complexes 1 and 2, and the hydrocarbonate coordinates with Ni(II) in a didentate fashion in complex 3. The monomers of {[Ni(RR-L)]2(µ-CO3)(H2O)}2+/{[Ni(SS-L)]2(µ-CO3)(H2O)}2+ are connected through hydrogen bonds to generate one-dimensional right- and left-handed helical chains in complex 1. The chiral nature of complex 2 has been confirmed by CD spectroscopy.
1 citations
References
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01 Jan 1996
3,515 citations
"Chiral resolution of l- and d-alani..." refers methods in this paper
...Empirical absorption corrections were applied by using the SADABS program [26]....
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TL;DR: This work shows an alternative mechanism that gives rise to asymmetric amplification based on the equilibrium solid-liquid phase behaviour of amino acids in solution, which is robust and can operate in aqueous systems, making it an appealing proposition for explaining one of the most tantalizing examples of asymmetric amplified.
Abstract: Ever since Pasteur noticed that tartrate crystals exist in two non-superimposable forms that are mirror images of one another--as are left and right hands--the phenomenon of chirality has intrigued scientists. On the molecular level, chirality often has a profound impact on recognition and interaction events and is thus important to biochemistry and pharmacology. In chemical synthesis, much effort has been directed towards developing asymmetric synthesis strategies that yield product molecules with a significant excess of either the left-handed or right-handed enantiomer. This is usually achieved by making use of chiral auxiliaries or catalysts that influence the course of a reaction, with the enantiomeric excess (ee) of the product linearly related to the ee of the auxiliary or catalyst used. In recent years, however, an increasing number of asymmetric reactions have been documented where this relationship is nonlinear, an effect that can lead to asymmetric amplification. Theoretical models have long suggested that autocatalytic processes can result in kinetically controlled asymmetric amplification, a prediction that has now been verified experimentally and rationalized mechanistically for an autocatalytic alkylation reaction. Here we show an alternative mechanism that gives rise to asymmetric amplification based on the equilibrium solid-liquid phase behaviour of amino acids in solution. This amplification mechanism is robust and can operate in aqueous systems, making it an appealing proposition for explaining one of the most tantalizing examples of asymmetric amplification-the development of high enantiomeric excess in biomolecules from a presumably racemic prebiotic world.
342 citations
TL;DR: The exogenous delivery of cometary and asteroidal material is observed today and undoubtedly has showered the Earth through its prior history because carbonaceous meteorites contain amino acids displaying asymmetry that has the same sign (L) as terrestrial amino acids.
Abstract: The exogenous delivery of cometary and asteroidal material is observed today and undoubtedly has showered the Earth through its prior history ([ 1 ][1]). Because carbonaceous meteorites contain amino acids displaying asymmetry that, if not as extensive, has the same sign (L) as terrestrial amino
297 citations
TL;DR: This critical review is devoted to an active field of research on chiral separation, membrane-based enantioseparation technique, which has potential for large-scale production of single-enantiomer compounds.
Abstract: This critical review is devoted to an active field of research on chiral separation, membrane-based enantioseparation technique, which has potential for large-scale production of single-enantiomer compounds. Adsorption-type enantioselective membranes and membrane-assisted resolution systems with non-enantioselective solid membranes have attracted much attention recently. The principles and recent developments of both enantioselective liquid and solid membranes and membrane-assisted processes for chiral resolution will be summarized comprehensively in this review, in which the contents are of interest to a wide range of readers in a variety of fields from analytical, organic and medicinal chemistry, to pharmaceutics and materials, to process engineering for fabricating pharmaceuticals, agrochemicals, fragrances and foods, and so on (148 references).
244 citations