Common b-Amino Acids - Nomenclature b-Alanine b-Alanine 1 is a widespread b-amino acid found in plants, fungi, animals, and bacteria (Schemes 1.5.1 and 1.5.2). This is not surprising, as b-Ala 1 is a precursor of pantothenic acid, an intermediate in coenzyme A biosynthesis [30], that is essential for primary metabolism in all kingdoms. Furthermore b-Ala moieties are found in the widespread non-proteinogenic amino acids carnosine (b-Ala-L-His) and anserine (3-methylcarnosine) [31]. Several peptides, cyclopeptides, and cyclo-depsipeptides of secondary metabolism contain b-Ala 1 as a non-proteinogenic building block, often combined with hydroxylated amino acids and D-amino acids. These peptides and peptolides are secondary metabolites from non-ribosomal protein biosynthesis that is typical for microorganisms. Accordingly, the Ca2+ channel

phascoline (15)

Scheme 1.5.1. Natural peptides, cyclopeptides, and cyclodepsipeptides related to b-Ala 1.

Scheme 1.5.2. Natural products related to b-AiB 2.

YM-170320 (21)

Scheme 1.5.2. Natural products related to b-AiB 2.

Tab. 1.5.1. Occurrence of natural b-amino acids related to proteinogenic «-amino acids.

b-Amino Acid [28] Type Source(s) of the Free Amino Acida and/or Related

Natural Productsb'c h2iu ß A

2 co2h

0 0

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