Cryo-bioorganic chemistry: Freezing effect on stereoselection of L- and DL-leucine cooligomerization in aqueous solution

T. Vajda, M. Hollósi

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Abstract

The chirality of L-/DL-leucine (50-50%) cooligomerization was investigated in liquid and frozen aqueous solutions. Cooligomerization was carried out by carbonyldiimidazole activation without initiator at an ambient (+ 22 °C) and frozen (- 18 °C) temperature, respectively. The separated samples obtained after different time intervals of treatment were completely hydrolyzed (HC1) and the diastereomeric L- and D-leucine derivates of Marfey's reagent (1-fluoro-2,4-dinitrophenyl-5-L-alanine amide) were then traced and evaluated by RP-HPLC analysis. After 9 days of oligomerization, the L-Leu content was slightly enhanced in the liquid (57%) and somewhat more enhanced in the frozen (64%) samples. After 17 days, however, the L-Leu content had decreased in the liquid (53%) and frozen (56%) conditions. These L-enantiomer amplifications indicate that an L-antipode is preferentially incorporated into the α-helical turn of the oligomer in the earlier stage of cooligomerization, while, later, the D-antipode is also incorporated. The role of ice in the improved stereoselection is discussed. This is the first recorded example of the effect of freezing on stereoselection.

Original languageEnglish
Pages (from-to)343-346
Number of pages4
JournalCellular and Molecular Life Sciences
Volume58
Issue number2
DOIs
Publication statusPublished - Jan 1 2001

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Keywords

  • Cooligomerization
  • Enantiomeric excess
  • Freezing
  • Prebiotic chiral amplification
  • Stereoselection

ASJC Scopus subject areas

  • Molecular Medicine
  • Molecular Biology
  • Pharmacology
  • Cellular and Molecular Neuroscience
  • Cell Biology

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