Non-Protein Amino Acids and Peptides
Synthesis and Screening of Non-Protein Amino Acids and Peptides as Potential Constituents of Radiomodifying and Pharmacological Agents
Tech Area / Field
- CHE-SYN/Basic and Synthetic Chemistry/Chemistry
- MED-DRG/Drug Discovery/Medicine
8 Project completed
Senior Project Manager
Bunyatov K S
Institute of Biotechnology, Armenia, Yerevan
- The Scientific Centre of Radiation Medicine and Burns, Armenia, Yerevan
- Universite de Paris-Sud / Institut de Chimie Moleculaire et des Materiaux D’Orsay, France, Orsay
Project summaryThe goal of the project is to synthesize non-protein amino acids and peptides that contain various side-chain aliphatic, aromatic and heterocyclic substituents and to study their radio modifying and metabolic activities.
Nowadays optically active non-protein a-amino acids of an unusual structure have found successful application in medicine, pharmacology, microbiology and other areas of science and engineering. Non-protein acids are wide spread in nature and there are a number of common biosynthetic pathways for their formation [1-5]. It is known that replacement of protein a-amino acids by the corresponding non-protein analogies in peptide component of some medicines increases stability to the proteolytic enzymes action that results in prolongation of their effect . Optically active a-amino acids of non-protein origin are the important components of various antitumor drugs - antibiotics, both pharmacologically and physiologically active peptides and other medicines. Among such kind of antibiotics are Peucinostatin A, Tuberactinomicin, Bleomycin, Edenin, Capriomicin, Dactinomycin, Leuprolide, Octreotide and Tuftsine etc. [7-11]. Non-protein amino acids are successfully used also in microbiology in selection of amino acids strain-producers . The wide spectrum of non-protein amino acids application requires development of their chemical synthesis. It is worth to mention that non-protein a-amino acids are physiologically active when they are involved in medicines composition as optically active isomers. The most appropriate approach to produce optically active amino acids of an unusual structure is asymmetric synthesis, providing the making of optically active amino acids directly, omitting the stage of racemates separation to optically active antipodes.
For the past years within the framework of International scientific programs as INTAS, INCO-COPERNICUS and ISTC we had a success in developing the universal methods for asymmetric synthesis of non-protein a-amino acids containing various side-chain aliphatic, aromatic and heterocyclic substituents (ISTC Project A-356). The background of these methods is a chiral plane-square complex of ion NiII of a Schiff’s base of amino acids or dehydroamino acids with chiral auxiliaries based on natural (S)-proline amino acid [13, 14] (Scheme).
The high-selective methods (d.e. 85-90%) of the asymmetric synthesis of more than 50 optically active (S)-a-amino acids with various side-chain substituents have been developed via C-alkylation of amino acid moieties in A complexes and nucleophilic addition of dehydroamino acid fragments in B complexes using the chiral N-benzyl-(S)-proline (X=H, ÂÐÂ)-based auxiliary [15-18]. This chiral (R)-proline-based auxiliary allows also to synthesize the same amino acids of (R)-absolute configuration. In the case of chiral auxiliary containing N-3,4-dichlorobenzyl-(S)-proline (X=3,4-CI2, CÐÂ) the incorporation of electron-acceptor substituents into the aromatic ring of N-benzylproline moiety resulted in sharp increase of reactivity of amino acid and dehydroamino acid moieties of A and B complexes (appr. 5-10 times) and stereoselectivity of the synthesis, as well (up to 98%). Within the framework of the proposed project it is supposed to synthesize new generations of chiral auxiliaries (X=2-CI, 2,6-CI2, 2,4-CI2, CI5, NO2, 3,4-F2, 2,6-F2, F5, 2,6-Me2, 3,4-Me2, 2,6-Et2 and 3,4-Et2, etc.) and use these auxiliaries purposeful in reactions of the asymmetric synthesis of new optically active non-protein amino acids as potential constituents of both physiologically and pharmacologically active peptides and other medicines. No doubt, the synthesis of new modified chiral auxiliaries that contain various electron-acceptor and electron-donor substituents in the aromatic ring of N-benzylproline moiety, will promote first the high-selective and high-rate asymmetric synthesis of amino acids, and second, will open an opportunity to obtain new optically active a-, b- and g- substituted a-amino acids with various side-chain aliphatic, aromatic and heterocyclic substituents the synthesis of which was failed while using chiral BPB. In the case of N-Form-Met and N-BOC-Met containing di-and tri-peptides the increase of their hemotactic and antagonistic activities was demonstrated while non-protein amino acids were incorporated into a peptide chain, in particular, by replacing (S)-alanine by (S)- a-allyl-L-alanine, or (S)-b-phenylalanine by (S)-a-methyl-b-phenylalanine. Medicines with adrenergic action are also of interest; in particular, b-adrenoblockers containing fragments of non-protein amino acids and also derivatives of optically active a-amino acids bound with various heterocyclic compounds. Taking as a background the experience of the specialists of the Institute of Fine Organic Chemistry (IFOC) NAS RA in the synthesis of the certain pharmacophoric fragment-based substances with cardiovascular action and their pharmacological study, a new level of pharmacological effect might be achieved. [19, 20].
The experience of our specialists in studies of antioxidant and protective properties of DMSO and other biocomplexes used as protectors was applied while testing the two synthesized non-protein amino acids: b- imidazolyl -L-alanine and a-methyl -L-phenylalanine [21, 22]. According to the preliminary results these compounds demonstrated physiological activity in nuclear-cell structure of mammals. The dependence of some cytogenetic characteristics (chromosomal aberration frequency, proliferation activity of bone-brain cells) on dosage of compounds was observed. Based on the data obtained it was assumed, that these synthesized compounds might have radio modifying properties. The screening of the chemical compounds possessing radio modifying properties (radio protection, early therapy, radio sensitizers, radio mimetic etc.) is necessary for new drugs discovery in radiation medicine, clinical radiobiology and radiation safety as a whole. New radio modification drugs discovery is especially actual in Armenia, where the atomic power station located on a small territory with rather high density of population which increases the risk in the cases of man-caused accidents or acts of terrorism on nuclear objects, and, also it is necessary because there are Chernobyl (the atomic catastrophe in1986 in Ukraine) liquidators and employes of the mining industry in Armenia for which the post radiation recovery agents are of utmost importance. Study of radio modifying compounds action will be useful for the identification of new classes of both radio protective and sensitizing (therapeutic, radiomimetic and antitumor) compounds, which can be recommended for pharmacological researches. Screening of a variety of chemical compounds to establish their modifying properties will contribute to "structure - function" and "dose - effect" relationship knowledge.
According to our data a number of the synthesized non-protein amino acids were shown to have an inhibitory effect on the growth of corynebacteria strains, but it has been restored by addition of the corresponding natural amino acid. The obtained results testified to their potential use in the selection of amino acid producers, since the selection of mutants resistant to analogies of natural amino acids is a universal method for selection of producers with the disturbed regulation of the target product biosynthesis. This approach was applied for successful construction of lysine, valine and phenylalanine producers [23, 24].
To reveal metabolic activities of the non-protein compounds it is supposed to investigate the effect of the synthesized compounds and radiation on the oxidative stress (super oxide dismutase (SOD), peroxidase) and also to detect the synthesized compounds toxicity and possible side effects (effect on skin, mucous, etc.). Studies of the synthesized compounds influence on regulation of the membrane lipids metabolism will allow estimating the role of these processes in pathogenesis of both radiation disease and the complications caused.
Studies on the metabolic activities of non-protein amino acids assume also investigation of their interaction with the key enzymes of the microorganisms that interact with natural amino acids: amino transferases, phosphoenolpyruvat – carboxylase, pyruvat- carboxylase, pyruvat-dehydrogenase. The planned studies on the influence of non-protein compounds on the activity of key enzymes, including the methodology of molecular modeling, will allow expanding our knowledge in molecular interactions and will reveal new targets for the screening of pharmacological and other bioactive preparations.
Within the framework of the proposed project it is supposed to synthesize new generations of chiral auxiliaries and use these auxiliaries purposeful in reactions of the asymmetric synthesis of new optically active non-protein amino acids as potential constituents of both physiologically and pharmacologically active peptides and other medicines. It is also supposed to study the action of non-protein amino acids and peptides on their basis on the mammalian chromosomes in vitro and in vivo and to carry out the screening of the chemical compounds possessing radio modifying properties, to study the effect of non-protein compounds and radiation on oxidative stress, to study the inhibiting action of the synthesized compounds as an amino acid analog on the growth of corynebacteria strains, to carry out the pharmacological screening of derivatives of optically active–amino acids bounded with various heterocyclic compounds, to study the toxicological characteristics of the synthesized compounds, to study the non-protein compounds interaction with bacterial enzymes, to study the potential interaction of the synthesized compounds with known molecular targets via molecular modeling.
The project will fulfill the objectives of ISTC in the following way: providing weapons scientists opportunities to redirect their talents to peaceful activities; promoting integration of scientists into the International scientific community; supporting basic and applied research and technology development for peaceful purposes. The role of foreign collaborators considers as an information exchange in the course of Project implementation, comments to the technical reports, and discussions of results.