Exploration of Naturally Occurring γ-amino acids in the Design of Foldamers and Biologically Active Peptidomimetics

Abstract

Extensive efforts have been made over the years to design protein structure mimetics using a variety of unnatural amino acid building blocks. The advancement in the field of peptide foldamers not only facilitated understanding the mechanism of folding but also proved to be relevant in the field of drug discovery, molecular recognition and bio-catalysis. Perhaps, the oligomers of the b and g amino acids are among the most extensively studied unnatural oligomers. Our previous studies have shown the utility of g-amino acids in the design of helices, b-hairpins, b-double helices, and multi-stranded b-sheets. In the present study, we have reported a cost-effective, efficient and racemize free protocol for the synthesis of b-amino alcohols using 2-MBT and further utilized them to synthesize g4-amino acids, β-hydroxy g-amino acids, β-keto g-amino esters and E-vinylogous amino acids. Later, we explored naturally occurring β-hydroxy g-amino acids (statine) in the design of peptide foldamers. Further, we have examined the inhibitory potency of a, γ-hybrid peptides against the γ-secretase, a multi-subunit protease complex known to be responsible for the pathogenesis of Alzheimer's disease. We have also utilized β-hydroxy γ-amino acid to design proteolytically stable water-soluble analogues of pepstatin (a universal aspartic acid protease inhibitor) and studied their inhibitory activity against proteases. We have also studied antimicrobial properties of short hybrid cationic lipopeptides containing β-hydroxy γ-amino acids and water-soluble cationic β-hairpins composed of E-vinylogous amino acids with lipid chain at the N-terminal. These peptides have displayed broad-spectrum antimicrobial activities against various microbial strains. Finally, we have shown the transformation of amino acids β-keto esters, precursors for the synthesis statines, into 1,4-dihydropyridines. Overall, the synthesis, conformational properties, inhibitory activity against the aspartic acid proteases, antimicrobial activity of γ4 and functionalized γ4-amino acids have been reported in this thesis that open wide opportunities to further, explore them as building blocks for the design of biologically active peptidomimetics.