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RESEARCH ARTICLE Open Access Condensation oscillations in the peptidization of phenylglycine

By Mieczysław Sajewicz, Monika Gontarska, Dorota Kronenbach, Marcin Leda, Teresa Kowalska and Irving R Epstein

Abstract

In earlier studies, we showed that certain low-molecular-weight carboxylic acids (profens, amino acids, hydroxy acids) can undergo spontaneous in vitro chiral conversion accompanied by condensation to from oligomers, and we proposed two simple models to describe these processes. Here, we present the results of investigations using non-chiral high-performance liquid chromatography with diode array detector (HPLC-DAD) and mass spectrometry (MS) on the dynamics of peptidization of S-, R-, and rac-phenylglycine dissolved in 70 % aqueous ethanol and stored for times up to one year. The experimental results demonstrate that peptidization of phenylglycine can occur in an oscillatory fashion. We also describe, and carry out simulations with, three models that capture key aspects of the oscillatory condensation and chiral conversion processes. Background The remarkable phenomenon of spontaneous in vitro oscillatory chiral conversion of selected profens, amino acids, and hydroxy acids has been the focus of our attention for some time. We first observed oscillatory chiral conversion in selected profens: S(+)-ibuprofen, S (+)-naproxen, S,R(±)-2-phenylpropionic acid, S(+)-flurbiprofen, R(-)-flurbiprofen, and S,R(±)-ketoprofen [1-3]. Later we described an analogous behavior in several amino acids: L-alanine, L-a-phenylalanine, and L-tyrosine [4-6]. We have characterized similar phenomena in selected hydroxy acids [7,8] (L-lactic acid, R-a-hydroxybutyric acid, S-a-hydroxybutyric acid, R-mandelic acid, and S-mandelic acid) as well. Most of these oscillatory chiral conversions take place with the acid samples dissolved in 70 % aqueous ethanol. The general scheme of these chiral conversions can be simply summarized as enantiomer + � enol � enantiomer (1) If we consider chiral conversion of selected carboxylic acids in aqueous solution in greater detail, then eq. (1) can be written as [9]

Year: 2013
OAI identifier: oai:CiteSeerX.psu:10.1.1.320.1134
Provided by: CiteSeerX
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