Vitaly M. Boitsov

Rate equation approach to understanding the ion-catalyzed formation of peptides

The salt-induced peptide formation is important for assessing and approaching schemes of molecular evolution. Here, we present experimental data and an exactly solvable kinetic model describing the linear polymerization of L-glutamic amino acid in water solutions with different concentrations of KCl and NaCl. The length distributions of peptides are well fitted by the model. Strikingly, we find that KCl considerably enhances the peptide yield, while NaCl does not show any catalytic effect in most cases under our experimental conditions. The greater catalytic effect of potassium ions is entirely interpreted by one and single parameter, the polymerization rate constant that depends on the concentration of a given salt in the reaction mixture. We deduce numeric estimates for the rate constant at different concentrations of the ions and show that it is always larger for KCl. This leads to an exponential increase of the potassium- to sodium-catalyzed peptide concentration ratio with length. Our results show that the ion-catalyzed peptides have a higher probability to emerge in excess potassium rather than in sodium-rich water solutions.

Reaction of 6,6-dimethylfulvene with aromatic imines in the presence of Lewis acids

Formal aza-Diels-Alder (Povarov) reaction of 6,6-dimethylfulvene with aromatic imines is described for the first time.

Stereoselective cycloaddition of diphenylisobenzofuran to N-arylitaconimides

A reaction of 1,3-diphenylisobenzofuran with N-arylitaconimides gives the [4+2] cycloaddition products with the 11′-oxaspiro[pyrrolidine-3,9′-tricyclo[6.2.1.02,7]undeca-2′,4′,6′-triene-2,5-dione] skeleton as a single diastereomer.

A highly diastereoselective one-pot three-component 1,3-dipolar cycloaddition of cyclopropenes with azomethine ylides generated from 11H-indeno[1,2-b]-quinoxalin-11-ones

A simple and efficient method has been developed for the synthesis of complex compounds with spiro-fused 11H-indeno[1,2-b]quinoxaline and cyclopropa[a]pyrrolizine or azabicyclo[3.1.0]hexane moieties. All the products have been synthesized in good to high yields and excellent diastereoselectivity by one-pot three-component 1,3-dipolar cycloaddition reactions of various derivatives of cyclopropene with azomethine ylides. Azomethine ylides were in situ generated from 11H-indeno[1,2-b]quinoxalin-11-one derivatives and amines, such as N-substituted and N-unsubstituted α-amino acids, benzylamines, and also peptides (dipeptide Gly-Gly and tripeptide Gly-Gly-Gly). To understand the mechanism that allows for azomethine ylide generation followed by 1,3-dipolar cycloaddition, a quantum chemical investigation was performed. The anticancer activity of some of the obtained compounds against the human leukemia K562 cell line was evaluated by flow cytometry in vitro.

The Influence of Different Potassium and Sodium Ion Concentrations on the Rate of Abiogenic Peptide Synthesis

The physicochemical conditions of the aqueous environment at the dawn of biological evolution were of key importance for abiogenic peptide synthesis. Recently, we have shown theoretical and experimental evidence for the unique role of potassium ions in the exponential acceleration of undirected peptide synthesis from L-glutamic acid. These data have confirmed our previous hypothesis that the first protocell emerged in a potassium rather than sodium-rich aqueous solution (seawater). The present work provides experimental data for an interpretation of concentration dependence and of optimal effective concentration of potassium and sodium ions in L-glutamic acid peptide formation.