Chirality Transfer Research Articles

Chiral Transfer and Evolution in Cysteine Induced Cobalt Superstructures.

Chiral organic additives have unveiled the extraordinary capacity to form chiral inorganic superstructures, however, complex hierarchical structures have hindered the understanding of chiral transfer and growth mechanisms. This study introduces a simple hydrothermal synthesis method for constructing chiral cobalt superstructures with cysteine, demonstrating specific recognition of chiral molecules and outstanding electrocatalytic activity. The mild preparation conditions allow in situ tracking of chirality evolution in the chiral cobalt superstructure, offering unprecedented insights into the chiral transfer and amplification mechanism. The resulting superstructures exhibit a universal formation process applicable to other metal oxides, extending the understanding of chiral superstructure evolution. This work contributes not only to the fundamental understanding of chirality in self-assembled structures but also provides a versatile method for designing chiral inorganic nanomaterials with remarkable molecular recognition and electrocatalytic capabilities.

Novel Stereo‐Induction Pattern in Pudovik Addition/Phospha‐Brook Rearrangement Towards Chiral Trisubstituted Allenes

AbstractDespite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al., there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide‐mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha‐Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central‐to‐axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo‐induction pattern in the Pudovik addition/phospha‐Brook rearrangement cascade reaction.

Novel Stereo-Induction Pattern in Pudovik Addition/Phospha-Brook Rearrangement Towards Chiral Trisubstituted Allenes.

Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al., there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide-mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha-Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central-to-axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo-induction pattern in the Pudovik addition/phospha-Brook rearrangement cascade reaction.

Observation of Chiral Channels in Helical Covalent Organic Frameworks.

Unraveling the mechanism of chirality transfer across length scales is crucial to the rational development of functional materials with hierarchical chirality. The key obstacle is the lack of structural information, especially at the mesoscopic level. We report herein the structural identification of helical covalent organic frameworks (heliCOFs) with hierarchical chirality, which integrate molecular chirality, channel chirality, and morphology chirality into one crystalline entity. Specifically, benefiting from the highly ordered structure of heliCOFs, the existence of chiral channels at the mesoscopic level has been confirmed by electron crystallography, and the handedness of these chiral channels has been directly determined through the stereopair imaging technique. Accordingly, the chirality transfer in heliCOFs from microscopic to macroscopic levels could be rationalized with a layer-rotating model that has been supported by both crystal structure analysis and theoretical calculations. Observation of chiral channels in heliCOFs not only provides unprecedented data for the understanding of the chirality transfer process but also sheds new light on the rational construction of highly ordered polymeric materials with hierarchical chirality.

Biomimetic Hydrogen‐Bonded G•C•G•C Quadruplex within a Tetraphenylethene‐Based Octacationic Spirobicycle in Water

In biological systems, nucleotide quadruplexes (such as G‐quadruplexes) in DNA and RNA that are held together by multiple hydrogen bonds play a crucial functional role. The biomimetic formation of these hydrogen‐bonded quadruplexes captured by artificial systems in water poses a significant challenge but can offer valuable insights into these complex functional structures. Herein, we report the formation of biomimetic hydrogen‐bonded G•C•G•C quadruplex captured by a tetraphenylethene (TPE) based octacationic spirobicycle (1). The spirobicyclic compound possesses a three‐dimensional (3D) crossing dual‐cavity structure, which enables the encapsulation of four d(GpC) dinucleotide molecules, thereby realizing 1:4 host‐guest complexation in water. The X‐ray structure reveals that four d(GpC) molecules further form a two‐layer G•C•G•C quadruplex with Watson‐Crick hydrogen bonds, which are stabilized within the dual hydrophobic cavities of 1 through the cooperative non‐covalent interactions of hydrogen bonds, CH···π interactions, and hydrophobic effect. Due to the dynamically‐rotational propeller chirality of TPE units, 1 with adaptive chirality can further serve as a chiroptical sensor to exhibit opposite Cotton effects with mirror‐image CD spectra for the pH‐dependent hydrogen‐bonded assemblies of d(GpC) including the Watson‐Crick G•C•G•C (pH 9.22) and Hoogsteen G•C+•G•C+ (pH 5.74) quartets through the host‐guest chirality transfer in water.

Biomimetic Hydrogen-Bonded G•C•G•C Quadruplex within a Tetraphenylethene-Based Octacationic Spirobicycle in Water.

In biological systems, nucleotide quadruplexes (such as G-quadruplexes) in DNA and RNA that are held together by multiple hydrogen bonds play a crucial functional role. The biomimetic formation of these hydrogen-bonded quadruplexes captured by artificial systems in water poses a significant challenge but can offer valuable insights into these complex functional structures. Herein, we report the formation of biomimetic hydrogen-bonded G•C•G•C quadruplex captured by a tetraphenylethene (TPE) based octacationic spirobicycle (1). The spirobicyclic compound possesses a three-dimensional (3D) crossing dual-cavity structure, which enables the encapsulation of four d(GpC) dinucleotide molecules, thereby realizing 1:4 host-guest complexation in water. The X-ray structure reveals that four d(GpC) molecules further form a two-layer G•C•G•C quadruplex with Watson-Crick hydrogen bonds, which are stabilized within the dual hydrophobic cavities of 1 through the cooperative non-covalent interactions of hydrogen bonds, CH···π interactions, and hydrophobic effect. Due to the dynamically-rotational propeller chirality of TPE units, 1 with adaptive chirality can further serve as a chiroptical sensor to exhibit opposite Cotton effects with mirror-image CD spectra for the pH-dependent hydrogen-bonded assemblies of d(GpC) including the Watson-Crick G•C•G•C (pH 9.22) and Hoogsteen G•C+•G•C+ (pH 5.74) quartets through the host-guest chirality transfer in water.

Cu2+-Dominated Chirality Transfer from Chiral Molecules to Concave Chiral Au Nanoparticles.

Foreign ions as additives are of great significance for realizing excellent control over the morphology of noble metal nanostructures in the state-of-the-art seed-mediated growth method; however, they remain largely unexplored in chiral synthesis. Here, we report on a Cu2+-dominated chiral growth strategy that can direct the growth of concave chiral Au nanoparticles with C3-dominant chiral centers. The introduction of trace amounts of Cu2+ ions in the seed-mediated chiral growth process is found to dominate the chirality transfer from chiral molecules to chiral nanoparticles, leading to the formation of chiral nanoparticles with a concave VC geometry. Both experimental and theoretical results further demonstrate the correlation between the nanoparticle structure and optical chirality for the concave chiral nanoparticle. The Cu2+ ion is found to dominate the chiral growth by selectively activating the deposition of Au atoms along the [110] and [111] directions, facilitating the formation of the concave VC. We further demonstrate that the Cu2+-dominated chiral growth strategy can be employed to generate a variety of concave chiral nanoparticles with enriched geometric chirality and desired chiroptical properties. Concave chiral nanoparticles also exhibit appealing catalytic activity and selectivity toward electrocatalytic oxidation of enantiomers in comparison to helicoidal nanoparticles. The ability to tune the geometric chirality in a controlled manner by simply manipulating the Cu2+ ions as additives opens up a promising strategy for creating chiral nanomaterials with increasing architectural diversity for chirality-dependent optical and catalytic applications.

Theory of Chiral Electrodeposition by Micro-Nano-Vortexes under a Vertical Magnetic Field-2: Chiral Three-Dimensional (3D) Nucleation by Nano-Vortexes

The contributions of magnetohydrodynamic (MHD) vortexes to chiral electrodeposition in a vertical magnetic field were theoretically examined based on the three-generation model of the 2D nucleus, 3D nucleus, and screw dislocation; for the vortexes to rotate in the second and third-generation, the kinematic viscosity must be at least 10−18 and 10−30 times lower than the ordinary value in the first generation, i.e., almost equal to zero. This implies that the ionic vacancy created on the electrode surface works as an atomic-scale lubricant. At the same time, the vortexes played three roles: promotion and suppression of nucleation, and transport of the chirality from the upper generation to the lower generation through precessional motion. Then, the rule of the chirality transfer was established, and finally, the relationship between the chiral activity and magnetic field was clarified in the presence and absence of chloride ions.

High Internal Phase Emulsion for Constructing Chiral Helical Polymer-Based Circularly Polarized Luminescent Porous Materials.

Polymerized high internal phase emulsions (polyHIPEs) with circularly polarized luminescence (CPL), as an interesting class of porous materials, are of great significance for the development of CPL porous materials but have not been reported so far. Herein, we report the construction of polyHIPE-based CPL porous materials, taking advantage of an adsorption strategy. The pristine polyHIPEs constructed by chiral helical polymers, which acted as a chiral microenvironment, were fabricated by coordination polymerization of chiral acetylene monomers (R/S-SA) using HIPEs as templates. Achiral fluorescent small molecules were dispersed in the pores of the 3D porous organic chiral polymer matrix provided by polyHIPEs through the adsorption strategy, and CPL-active porous materials with blue, cyan, and green emissions were constructed using a fluorescence-selective absorption mechanism that does not rely on chirality transfer at the molecular level. The maximum luminescence dissymmetry factor (glum) value was -2.6 × 10-2. This work establishes a new and simple way for developing CPL porous materials.

Tuning the Geometry and Optical Chirality of Pentatwinned Au Nanoparticles with 5-Fold Rotational Symmetry.

Chirality transfer from chiral molecules to chiral nanomaterials represents an important topic for exploring the origin of chirality in many natural and artificial systems. Moreover, developing a promising class of chiral nanomaterials holds great significance for various applications, including sensing, photonics, catalysis, and biomedicine. Here we demonstrate the geometric control and tunable optical chirality of chiral pentatwinned Au nanoparticles with 5-fold rotational symmetry using the seed-mediated chiral growth method. A distinctive growth pathway and optical chirality are observed using pentatwinned decahedra as seeds, in comparison with the single-crystal Au seeds. By employing different peptides as chiral inducers, pentatwinned Au nanoparticles with two distinct geometric chirality (pentagonal nanostars and pentagonal prisms) are obtained. The intriguing formation and evolution of geometric chirality with the twinned structure are analyzed from a crystallographic perspective upon maneuvering the interplay of chiral molecules, surfactants, and reducing agents. Moreover, the interesting effects of the molecular structure of peptides on tuning the geometric chirality of pentatwinned Au nanoparticles are also explored. Finally, we theoretically and experimentally investigate the far-field and near-field optical properties of chiral pentatwinned Au nanoparticles through numerical simulations and single-particle chiroptical measurements. The ability to tune the geometric chirality in a controlled manner represents an important step toward the development of chiral nanomaterials with increasing architectural complexity for chiroptical applications.

Copper(I)‐Catalyzed Enantioselective Synthesis of Chiral Cyclohexenylallenes and Transfer of Axial to Center Chirality by Ytterbium(III) Catalyzed [4+2] Cycloaddition

Chiral cyclohexenylallenes are readily accessed from 1‐enynes, aldehydes and chiral secondary amines in good yields (up to 79% yield) with excellent enantioselectivities (up to 99% ee), through CuI catalyzed the formation of chiral propargylamine intermediates.  Subsequent Yb(OTf)3 catalyzed [4+2] cycloaddition reaction of cyclohexylallenes with the dienophiles tetracyanoethylene and diethyl acetylenedicarboxylate afforded the corresponding bicyclic products in 69‐75% yield and 84‐90% ee.

Chiral Ni(Ⅱ)-Based coordination polymers with helixes and dinuclear clusters constructed from lactate synthons

Chiral coordination polymers [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15-R), [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15–S), [Ni((R)-ceba) (4,4′-dib) (H2O)0.5] (HU16-R) and [Ni((S)-ceba) (4,4′-dib) (H2O)0.5](HU16–S) were prepared from lactate-derived synthons and different N-donor linkers under hydrothermal conditions (H2ceba = 4-(1-carboxyethoxy)benzoic acid, 1,3-dpp = 1,3-di(pyridine-4-yl)propane, 4,4′-dib = 4,4′-di (1H-imidazole-1-yl)-1,1′-biphenyl). Structural analysis confirmed that that all complexes are three-dimensional frameworks containing dinuclear [Ni2(CO2)2(H2O)]2+ clusters. In addition, four types of helical structures were also obtained though chiral transfer and asymmetric induction from chiral synthons among them. (R)-ceba2- anions and Ni(Ⅱ) ions were bridged together to construct right-handed (R)-ceba-Ni chains in HU15-R and HU16-R, while (S)-ceba2- anions were linked by Ni(Ⅱ) ions to build right-handed (S)-ceba-Ni chains in HU15–S and HU16–S. Apart from chiral synthons, achiral linkers 1,3-dpp and 4,4′-dib assembled with Ni(Ⅱ) ions to form single 1,3-dpp-Ni chains in HU15-R and HU15–S and double 4,4′-dib-Ni chains in HU16-R and HU16–S, respectively. Meanwhile, the introductions of N-donor ligands resulted in varied topological structures. HU15-R and HU15–S are 4-connected dia nets, while HU16-R and HU16–S are 8-connected frameworks. Moreover, magnetic experiments indicated that antiferromagnetic interactions exist in these complexes.

Cholesterol-decorated porphyrin with circularly polarized luminescence: Design, synthesis and properties

Porphyrin was an excellent near-infrared dye but its rigid planar structure is not favorable for producing circularly polarized luminescence (CPL) property. Chirality transfer is an effective strategy to realize the CPL emission for achiral fluorescent unit. In this study, porphyrin derivatives with four cholesterol groups and dodecyl groups B4C and B4D were designed and synthesized. B4C and B4D exhibited good near-infrared emission in both solution and aggregated states. The solid film of B4C emitted strong left CPL fluorescence, while this CPL signal in mesomorphic film was stronger and switched to right CPL emission. The fluorescence dissymmetry factor (glum) of B4C was as high as 2.31×10−2. These results suggested the effective chirality transfer from cholesterol units to porphyrin units based on spiral columnar liquid crystalline stacking and the CPL signal of B4C was tunable by temperature, supplying a good way on design and synthesis of CPL material with tunable CPL signal based on achiral dyes.

Enigma of Pyramidal Neurons: Chirality-Centric View on Biological Evolution. Congruence to Molecular, Cellular, Physiological, Cognitive, and Psychological Functions

The mechanism of brain information processing unfolds within spatial and temporal domains inherently linked to the concept of space–time symmetry. Biological evolution, beginning with the prevalent molecular chirality, results in the handedness of human cognitive and psychological functions (the phenomena known as biochirality). The key element in the chain of chirality transfer from the downstream to upstream processes is the pyramidal neuron (PyrN) morphology–function paradigm (archetype). The most apparent landmark of PyrNs is the geometry of the cell soma. However, “why/how PyrN’s soma gains the shape of quasi-tetrahedral symmetry” has never been explicitly articulated. Resolving the above inquiry is only possible based on the broad-view assumption that encoding 3D space requires specific 3D geometry of the neuronal detector and corresponding network. Accordingly, our hypothesis states that if the primary function of PyrNs, at the organism level, is sensory space symmetry perception, then the pyramidal shape of soma is the best evolutionary-selected geometry to support sensory-motor coupling. The biological system’s non-equilibrium (NE) state is fundamentally linked to an asymmetric, non-racemic, steady state of molecular constituents. The chiral theory of pyramidal soma shape conceptually agrees that living systems have evolved as non-equilibrium systems that exchange energy with the environment. The molecular mechanism involved in developing PyrN’s soma is studied in detail. However, the crucial missing element—the reference to the fundamental link between molecular chirality and the function of spatial navigation—is the main obstacle to resolving the question in demand: why did PyrNs’ soma gain the shape of quasi-tetrahedral symmetry?

Optical Activity and Excitonic Characteristics of Chiral CdSe Quantum Dots.

Introduction of chirality to colloidal semiconductor quantum dots (QDs) triggers a chiroptical effect. However, there remains a knowledge gap in the mechanism of chirality transfer and amplification from molecules to QDs. By time-dependent density functional theory calculations combined with a correlated electron-hole picture, we explored the chiroptical activity of CdSe QDs decorated with different chiral monocarboxylic acids from an excitonic perspective. Our calculations showed strong circular dichroism (CD) signals in the visible region for the chiral CdSe QDs. The excitonic states with large CD originate from QDs, while the chiral molecules break the orthogonality between electric and magnetic transition dipoles, which synergistically facilitates the prominent dissymmetric effect. The considered monocarboxylic acid chiral molecules all favor the bidentate adsorption configuration of the carboxyl group on the CdSe surface, endowing an identical CD signature but distinct excitonic characteristics. These findings are crucial for the regulation of chirality and excitons in semiconductor QDs to develop excitonic devices.

Tunable Circularly Polarized Luminescence by Confining Dye Molecules within Chiral Layered Metal–Organic Framework

AbstractCircularly polarized luminescence (CPL) active materials have attracted widespread attention because of their potential applications. Nonetheless, it is still a great challenge to fabricate CPL materials with both high fluorescence quantum efficiency (Φ) and high luminescent asymmetry factor (glum). According to the unique structure characteristics of chiral layered metal–organic frameworks (CLMOFs), herein a novel strategy to construct high‐performance CPL materials, by utilizing the confinement effect of CLMOFs is developed. Conjugate dye molecules, such as fluorescent brighteners, fluorescein, and rhodamine B, which are readily subjected to aggregation‐caused quenching (ACQ) effect, are successfully intercalated into CLMOF matrix, affording blue, yellow–green, and red CPL, respectively. Both high Φ and glum values of up to 91% and 0.069 are obtained, owing to the distinct confinement effect of CLMOFs. After confining dye molecules within CLMOF, the ACQ effect is effectively inhibited, which is beneficial for fluorescence enhancement; simultaneously, the chirality transfer from CLMOF matrix to dyes by controlling their arrangement in the chiral confinement microenvironment, leading to the high glum values. Based on the full‐color and strong CPL, a multi‐dimensional code system is proposed. This work paves a new avenue to design and assemble CPL materials with high Φ and glum, which can be widely adopted.

Three-Dimensional Homochiral Covalent Organic Frameworks with Intrinsic Chiral qzd Topology.

Although a variety of chiral porous framework materials have been reported, there are few examples known to combine molecular chirality, helicity, and three-dimensional (3D) intrinsically chiral topology in one structure, which is beneficial for chirality transfer and amplification. Here, we report the synthesis of the first two 3D covalent organic frameworks (COFs) with an intrinsic chiral qzd topology, which exhibit unusual integration of various homochiral and homohelical features. By imine condensation of 4-connected porphyrin tetraamines and 2-connected enantiopure diene dialdehyde, we prepared two isostructural COFs with a noninterpenetrated qzd topology. The specific geometry and conformation flexibility of the V-shaped diene linker control the alignment of square-planar porphyrin units with rotational linkages and facilitate the creation of homochiral extended porous structures that feature a helical arrangement of porphyrins. Post-synthetic metalation of CCOF 23 with Rh(I) affords a heterogeneous catalyst for the asymmetric Michael addition reaction of aryl boronic acids to 2-cyclohexenone, which shows higher enantioselectivities compared to their homogeneous counterparts, presumably due to the confined effect of helical channels. This finding will provide an impetus to explore multichirality materials, offering new insights into the generation and control of helicity, homochirality, and enantioselectivity in the solid state.

A chiral zeolite material with improved enantioselective catalytic properties prepared from readily accessible ephedrine alkaloids

Substituted-benzyl-containing N-methyl-ephedrinium derivatives (BMEP), prepared from the highly-accessible (1R,2S)- or (1S,2R)-ephedrine alkaloids, have been found to act as efficient structure-directing agents for the synthesis of chiral zeolite GTM-4 with –ITV framework structure, promoting the enantio-enrichment in one of the chiral crystalline polymorphs as a function of the organic handedness. Results of a systematic variation of substituents in the benzyl ring attached to the ephedrine core (with methyl-, fluoro- or chloro-groups in the different positions of the aromatic ring) revealed that F-containing SDAs brought about an improvement in the structure-directing ability toward the –ITV framework, giving asymmetric zeolite acid-catalysts that yielded notable enantiomeric excesses in the range of 40–45 % for the trans-stilbene oxide ring-opening with 1-butanol. Interestingly, the incorporation of a methyl group in ortho-position (oMBMEP) had a double positive effect: on the one hand, this SDA prevented the crystallization of the competing BEC phase, allowing the crystallization of the -ITV structure at higher temperature and with higher crystallinity, and on the other, it drove to GTM-4 asymmetric catalysts that yielded enantiomeric excesses up to 60 %, resulting in the chiral GTM catalysts with the best enantioselective properties found so far. Remarkably, our catalytic results show the same chiral activity (in terms of zeolite handedness) for GTM-4 materials prepared from benzyl-containing (1S,2S)-N-methyl-pseudoephedrinium (BMPS) and (1S,2R)-N-methyl-ephedrinium (BMEP) derivatives, thus suggesting that the host-guest transfer of chirality during crystallization with these chiral organic aromatic agents is imposed by the absolute configuration of the C1 atom to which the OH group is attached. The relatively high enantiomeric excess of 60 % achieved, combined with the high accessibility of the ephedrine chiral precursors used for the synthesis that enables the production of both crystalline handedness of the –ITV framework, bring these materials closer to a potential application as heterogeneous asymmetric catalysts for the synthesis of chiral compounds of interest.

Ligand Chirality Transfer from Solution State to the Crystalline Self-Assemblies in Circularly Polarized Luminescence (CPL) Active Lanthanide Systems.

The synthesis of a family of chiral and enantiomerically pure pyridyl-diamide (pda) ligands that upon complexation with europium [Eu(CF3 SO3 )3 ] result in chiral complexes with metal centered luminescence is reported; the sets of enantiomers giving rise to both circular dichroism (CD) and circularly polarized luminescence (CPL) signatures. The solid-state structures of these chiral metallosupramolecular systems are determined using X-ray diffraction showing that the ligand chirality is transferred from solution to the solid state. This optically favorable helical packing arrangement is confirmed by recording the CPL spectra from the crystalline assembly by using steady state and enantioselective differential chiral contrast (EDCC) CPL Laser Scanning Confocal Microscopy (CPL-LSCM) where the two enantiomers can be clearly distinguished.

Symmetry breaking and chiral amplification in prebiotic ligation reactions.

The single chirality of biological molecules is a signature of life. Yet, rationalizing how single chirality emerged remains a challenging goal1. Research has commonly focused on initial symmetry breaking and subsequent enantioenrichment of monomer building blocks-sugars and amino acids-that compose the genetic polymers RNAand DNA as well as peptides. If these building blocks are only partially enantioenriched, however, stalling of chain growth may occur, whimsically termed in the case of nucleic acids as "the problem of original syn"2. Here, in studying a new prebiotically plausible route to proteinogenic peptides3-5, we discovered that the reaction favours heterochiral ligation (that is, the ligation of L monomers with D monomers). Although this finding seems problematic for the prebiotic emergence of homochiral L-peptides, we demonstrate, paradoxically, that this heterochiral preference provides a mechanism for enantioenrichment in homochiral chains. Symmetry breaking, chiral amplification and chirality transfer processes occur for all reactants and products in multicomponent competitive reactions even when only one of the molecules in the complex mixture exhibits an imbalance in enantiomer concentrations (non-racemic). Solubility considerations rationalizefurther chemical purification and enhanced chiral amplification. Experimental data and kinetic modelling support this prebiotically plausible mechanism for the emergence of homochiral biological polymers.