Homochiral oligopeptides via surface recognition and enantiomeric cross impediment in the polymerization of racemic phenylalanine <i>N</i>‐carboxyanhydride crystals suspended in water

Nery, José Geraldo; Eliash, Ran; Bolbach, G.; Weissbuch, Isabelle; Lahav, Meir

doi:10.1002/chir.20363

Cited by 17 publications

(40 citation statements)

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“…The templates may be either parallel, as described here for ValNCA, or antiparallel as reported in a previous study of the polymerisation of (R,S)-PheNCA. [16,17] The packing arrangement of (R,S)-LeuNCA presumably does not permit the formation of either architecture as the isotactic peptides are not formed in substantial quantities from this starting material.…”

Section: Resultsmentioning

confidence: 98%

“…In the case of racemic ap b sheets, isotactic chains of the same absolute configuration as the initiator will be formed in lower concentration. [17] If enantiomorphous pleated sheets are formed, those composed of isotactic oligopeptides of the same absolute configuration as the initiator will be formed in excess. [4] The MALDI-TOF mass spectra of the water-soluble and water-insoluble diastereoisomeric peptides generated in the polymerisation reaction of (R,S)-ValNCA crystals suspended in aqueous solutions containing the (S)-Val-OMe initiator are shown in Figure 6a and b. Oligopeptides comprising up to 14 repeat units were detected and we noticed that the water-soluble isotactic di-and tripeptides formed in excess are of the same absolute configuration as that of the initiator (Figure 6a).…”

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confidence: 99%

“…This disadvantage might be overcome if the short polymers of homochiral sequence (isotactic) would self-assemble into ordered architectures that could exert steric control on the ensuing process of chain elongation occurring at the polymer/crystal interface. [15][16][17] The operation of such interplay requires an understanding of the role played by the structure of the monomer crystal at the early stages of the reaction, its role in dictating the self-assembly of the formed peptides into supramolecular architectures, such as a helices or b sheets, and the ultimate role played by the latter as stereospecific or enantioselective templates in the ensuing stages of polymer propagation. Here, we provide support for this hypothesis for the solidstate polymerisation of racemic crystals of valine N-carboxyanhydride (ValNCA, Scheme 1) and leucine N-carboxyanhydride (LeuNCA) suspended in hexane or water solutions of a primary-amine initiator.…”

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confidence: 99%

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Homochiral Oligopeptides via a Lattice‐Controlled Polymerisation in Racemic Crystals of Valine N‐Carboxyanhydride Suspended in Aqueous Solutions

Eliash¹,

Nery²,

Rubinstein³

et al. 2007

Chemistry A European J

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As part of our program on the biochirogenesis of homochiral peptides, we report the formation of racemic parallel (p) beta sheets composed of alternating R and S chains of up to 14-15 repeat units of the same handedness through the polymerisation of (R,S)-valine N-carboxyanhydride (NCA) crystals suspended in aqueous solutions of a primary amine as the initiator. The occurrence of such a lattice-controlled reaction accompanied by a reduction in volume implies the operation of a mechanism that differs from that of the common solid-state polymerisation in vinyl systems. The topotacticity of the reaction is explained through the operation of a multistep nonlinear process comprising lattice control coupled with an asymmetric induction in the formation of homochiral short peptides followed by their self-assembly into racemic p beta sheets, which operate as efficient templates in the ensuing process of enantioselective chain elongation at the polymer/crystal interface. The composition of the diastereoisomeric libraries of oligopeptides was determined by MALDI-TOF and MALDI-TOF-TOF MS analyses of the products obtained from monomers enantioselectively labelled with deuterium. The structure of the p beta sheets could be determined by initiating the polymerisation reaction with water-soluble esters of enantiopure alpha-amino acids or short peptides. The same reaction performed with the monomer crystals suspended in hexane yielded a complex mixture of diastereoisomeric oligopeptides, thus highlighting the indispensable role played by water in controlling the stereoselectivity of the reaction. By contrast, polymerisation of (R,S)-leucine NCA crystals, with a different packing arrangement that presumably does not endorse the formation of periodic peptide templates, yielded, both in aqueous and hexane suspensions, libraries of peptides dominated by heterochiral diastereoisomers.

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Section: Resultsmentioning

confidence: 98%

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confidence: 99%

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confidence: 99%

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Homochiral Oligopeptides via a Lattice‐Controlled Polymerisation in Racemic Crystals of Valine N‐Carboxyanhydride Suspended in Aqueous Solutions

Eliash¹,

Nery²,

Rubinstein³

et al. 2007

Chemistry A European J

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“…However, during these studies a different mechanism was identified, which allowed the synthesis of isotactic polymers in these solid-state polymerization reactions. The isotacticity of the products was tested by tagging, enantioselectively, the S-enantiomers with deuterium and analyzing the distribution of the diastereoisomeric oligopeptides, using MALDI-TOF MS [65][66][67].…”

Section: Generation Of Isotactic Oligopeptides Via Polymerization In mentioning

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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“…Zweifellos sollten wir die Chirogenese kleiner Moleküle und Polymere mit Blick auf diejenigen Substrate und Prozesse überdenken, die in einem präbiotischen Szenario plausibel sind, [1] solange niemand mit einer passenderen Erklä-rung als einer zufälligen spontanen Racematspaltung aufwarten kann. [2] Die Verstärkung einer sehr kleinen Unausgewogenheit in einem Gemisch chiraler Moleküle wird durch Grundprinzipien der Stereochemie und der physikalischen Chemie gelenkt, z.…”

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Entstehung von Homochiralität unter präbiotischen Bedingungen

Cintas¹

2008

Angewandte Chemie

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Homochiral oligopeptides via surface recognition and enantiomeric cross impediment in the polymerization of racemic phenylalanine N‐carboxyanhydride crystals suspended in water

Cited by 17 publications

References 44 publications

Homochiral Oligopeptides via a Lattice‐Controlled Polymerisation in Racemic Crystals of Valine N‐Carboxyanhydride Suspended in Aqueous Solutions

Homochiral Oligopeptides via a Lattice‐Controlled Polymerisation in Racemic Crystals of Valine N‐Carboxyanhydride Suspended in Aqueous Solutions

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

Entstehung von Homochiralität unter präbiotischen Bedingungen

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