New Naturally Occurring Amino Acids

The majority of the 500 or so naturally occurring amino acids known today were discovered during the last 30 years, for example during the search for new antibiotics in the culture media of microorganisms, or as components of the antibiotics in fungi, seeds, in numerous plants and fruits, and in the body fluids of animals. Some 240 of these amino acids occur free in nature, some only as intermediates in metabolism. This article provides an overview of the developments that have taken place in this area since 1956 when the last review appeared. Summary accounts are presented, dealing with new unsaturated amino acids, cyclopropane- and cyclobutane-amino acids, heterocyclic amino acids, halogen-containing amino acids sulfur-, selenium- and phosphorus-containing amino acids as well as aliphatic amino acids. In a few cases, e. g. betalamic acid and muscaflavin, the biosynthesis is described in detail.