Chapter 2 - Synthetic Studies Toward Nonribosomal Peptides

Abstract

Progress in the subject of peptides and amino acids has enabled us to think beyond the standard 20 proteinogenic amino acids, the majority of which belong to a certain class of peptide secondary metabolites known as nonribosomal peptides (NRPs). The discovery of amino acids like pyrrolysine, selenocystine, D-amino acids, etc., (now classified as nonproteinogenic or nonstandard amino acids) has triggered research on nonnatural amino acids. NRPs like actinomycin, vancomycin, bleomycin, etc., are synthesized by NRP synthetases (independent of m-RNA) and, hence, have the scope for incorporation of noncoded nonproteinogenic amino acids. Their broad ranges of biological and pharmacological properties have made them a much sought after targets in research, special significance has been given to their isolation and chemical synthesis for their use as antibiotics, immunosuppressants, etc. In a broader sense, chemical synthesis of peptides with nonproteinogenic amino acids has become imminent in order to meet the need for better and effective drugs. With this review, it will be our sincere effort to present a concise yet informative article on the recent developments toward the chemical synthesis of these NRPs.