A-Aminobutyrate

Fig. 9. Stmcture of nisin where Dha = dehydroalanine Dhb = dehydrobutyrine Abu = a-aminobutyric acid Ala-S-Ala = me50-lanthionine and Abu-S-Ala = t/ireo-methyllanthionine. The first amino acid residue (Ala or Abu) of the lanthionine or methyUanthionine is a D residue all other amino...

MeVal = A-methylvaline and Abu = a-aminobutyric acid. The dotted lines indicate hydrogen bonds. 

Of the twenty amino acids that are normally found in proteins, only two contain sulfur, cysteine and methionine. Cysteine has long been recognized as being easily oxidized and this oxidation is associated with the loss of biological activity of many proteins. In recent years, it has been shown that methionine also shares these characteristics. Methionine was first isolated by Mueller19 and was one of the last amino acids discovered. Its structure was later proven to be y-methylthio-a-aminobutyric acid by Barger and Coyne20 who named the amino acid methionine as a contraction for its chemical name. 

Cyclic peptide from 11 amino acids. Preparation by fermentation of Tolypocladium inflatum Gams with addition of DL-a-aminobutyric acid to the fermentation medium. Isolation by homogenization of mycelium, extraction with 90 % methanol and column chromatographic purification. 

Scheme 5.25 2,4,6-Triisopropylbenzenesulfonamide of a-aminobutyric acid ligand for B-catalysed Diels-Alder reactions.

However, the amino acids were not necessarily formed in the gas phase. John Oro, one of the pioneers in prebiotic chemistry, carried out syntheses in the liquid phase by reacting HCN, NH3 and H2O at 353 K. The results were confirmed by Lowe et al. (1963) and developed further ten years later, Jim Ferris took them up and did considerable further work (Ferris et al., 1973, 1974). In all these simulation experiments, the simplest amino acids (glycine, alanine and in small amounts aspartic acid and a-aminobutyric acid) are, as expected, the main products the yields of glycine are around 1%, those of the other amino acids much lower. 

By means of a procedure described above, Hanson and Fittkau (HI) isolated seventeen different peptides from normal urine. One of them, not belonging to the main peptide fraction, consisted of glutamic acid, and phenylalanine with alanine as the third not definitely established component. The remaining peptides contained five to ten different amino acid residues and some unidentified ninhydrin-positive constituents. Four amino acids, i.e., glutamic acid, aspartic acid, glycine, and alanine, were found in the majority of the peptides analyzed. Twelve peptides contained lysine and eight valine. Less frequently encountered were serine, threonine, tyrosine, leucine, phenylalanine, proline, hydroxyproline, and a-aminobutyric acid (found only in two cases). The amino acid composi-... 

Chiral 1,2,3-oxazaborolidines simply obtained from a-amino acid derived sulfonamides and borane were first applied in Diels-Alder reactions by Taliasu and Yamamoto228, and Helmchen and colleagues229. Yamamoto prepared catalysts from a-aminobutyric acid derived arylsulfonamides and found that the enantioselectivity of the reaction between... 

Novel Enzymes for Biotransformation and Resolution of Alpha-Amino Acids 81 5.03.4.2 Whole-Cell Procedure for Producing a-Aminobutyrate... 

When thiram (100 ppm) was inoculated with activated sludge (30 ppm) at 25 °C and pH 7.0 for 2 wk, 30% degraded. Metabolites included methionine, elemental sulfur, formaldehyde, dimethyldithiocarbamate-a-aminobutyric acid, and the corresponding keto acid (Kawasaki, 1980). 

Dimethyl-2,6-dinitroaniline, see Pendimethalin Dimethyl disulfide, see Aldicarb. Methyl mercaptan Dimethyldithiocarbamate, see Thiram Dimethyldithiocarbamate-a-aminobutyric acid, see... 

Cyclosporin A contains II amino acids, joined in a cyclic strncture by peptide bonds. The structure is also stabilized by intramolecular hydrogen bonds. Only two of the amino acids, i.e. alanine and valine, are typical of proteins. The compound contains several A-methylated amino acid residues, together with the even less common L-a-aminobutyric acid and an Ai-methylated butenylmethylthreonine. There is one o-amino acid, i.e. o-alanine, and the assembly of the polypeptide chain is known to start from this residue. Many of the other natural cyclosporin structures differ only with respect to a single amino acid (the a-aminobutyric acid residue) or the number of amino acids that have the extra Ai-methyl group. 

Amino-acul complexes. frans-(0,X)-[CoX(aminoacidato)(dien)]Y (X == CN, NO2, or Cl Y = Br, Cl, or ClO aminoacid === Gly, a-aminobutyric acid, L-Ala. L-Val, L-Thr, or L-Pro) complexes have been isolated. The cyano-complexes were shown to exist in the new conformational isomeric endo- and cxo-forms. This refers to the position of the hydrogen atom bonded to the central N of dien w ith respect to the cyanide group. The tetramine ligands 1,3-diaminopropane, 3,7-diaza-l,9-nonanediamine (2,3,2-tet), and 4,7-diaza-1.10-decanediamine (2,2,3-tet) exhibit marked topological specificity in the complexes [Co(tetramine)(aa)] (aa = Gly. Ala, Val. or Sar). Thus a-[Co-(3,2,3-tet)aa] and P2-[Co(2,3,2-tet)aa] appear to be formed exclusively under the synthetic conditions employed. 

Alanine, aspartic acid, glutamic acid, tyrosine, leucine, phenylalanine and also a-amino-n-caproic acid and a-aminobutyric acid have in this way been separated by Fischer into their optically active isomers. To these must be added ornithine which was synthesised by Sorensen in 1903, and separated into d- and 1-ornithine in 1905. 

The coordination geometry of these Cu(III) complexes is presumed to be square planar, indicative of high field d complexes. This has been demonstrated in the crystal structure of deprotonated tri-a-aminobutyric acid, Cu "(H 2Aib3), in which the copper-donor atom bonds were found to be 0.12-0.17 A shorter than for the corresponding Cu(II) complex... 

The Pd-catalyzed amidocarbonylation was used for the synthesis of a-arylglycines that are antimicrobial agents and enzyme inhibitors.Thus, iV-acyl-a-arylglycines and other iV-acyl-a-amino acids were synthesized in highly efficient and economical manner under the standard conditions. In a similar manner, an advanced intermediate for the synthesis of antiepileptic Levetiracetam 7, iV-acetyl-a-aminobutyric acid 6, was synthesized in high yield from propanal and acetamide (Equation (1)). ... 

---