Aminoisobutyric

Hydroxyl Group. The OH group of cyanohydrins is subject to displacement with other electronegative groups. Cyanohydrins react with ammonia to yield amino nitriles. This is a step in the Strecker synthesis of amino acids. A one-step synthesis of a-amino acids involves treatment of cyanohydrins with ammonia and ammonium carbonate under pressure. Thus acetone cyanohydrin, when heated at 160°C with ammonia and ammonium carbonate for 6 h, gives a-aminoisobutyric acid [62-57-7] in 86% yield (7). Primary and secondary amines can also be used to displace the hydroxyl group to obtain A/-substituted and Ai,A/-disubstituted a-amino nitriles. The Strecker synthesis can also be appHed to aromatic ketones. Similarly, hydrazine reacts with two molecules of cyanohydrin to give the disubstituted hydrazine. 

RS- P-Aminoisobutyric acid (a-methyl-P-alanine) [10569-72-9] M 103.1, m 176-178 , 178-180 , 181-182 , R -(-)- isomer [144-90-1] m 183 , [a] -21 (c 0.43, HjO), pKes,(,) 3.7, pKEst(2) 10.2. Colorless prisms from hot H O, were powdered and dried in vacuo. The purity is checked by paper chromatography (Whatman 1) using ninhydrin spray to visualise the amino acid Rp values in 95% MeOH and n-PrOH/5N HCOOH (8 2) are 0.36 and 0.50 respectively. [Kupiecki and Coon Biochem Prep 7 20 7960 Pollack J Am Chem Soc 65 1335 7943.] The R-enantiomer, isolated from iris bulbs or human urine was crystd from H2O and sublimed in vacuo [Asen et al. J Biol Chem 234 343 7959]. The RS-hydrochloride was recrystd from EtOH/Et20 m 128-129 , 130° [Bbhme et al. Chem Ber92 1258, 1260, 1261 7959]. 

The effect of C ,C -disubstituted amino acids (aaAAs) on peptide secondary structure has been studied in recent years.2a d While longer side-chain C ,C -di-n-alkyl amino acids promote extended peptide conformation,23 alicyclic aaAAs, in which the Ca carbon forms a cyclic bridge with itself, such a 1-aminocyclopentane-l-carboxylic acid (Ac5c) and 1-aminocyclohexane-l-carboxylic acid (Ac6c), have helix-forming characteristics similar to those of 1 -aminoisobutyric acid (Aib).2ax... 

We present here a kinetic study of the decomposition of the N-bromo derivatives of alanine, aminoisobutyric acid and proline in alkaline medium, where the mechanism of decomposition is not fiilly understood. A discussion of the different microscopic mechanisms that can be proposed is done in the light of the obtained experimental results. 

In the case of the decomposition reaction of N-Br-aminoisobutyric acid and N-Br-proline, the absorbance-time data obtained at 289 nm and 293 nm respectively, were well fitted to first order integrated equations ... 

Fig. 2. Absorbance-time graph showing first order compliance for the decomposition reaction of N-Br-aminoisobutyric acid. [BrO"] = 2.0 x lO M, [Aib] = 0.02 M, [NaOH] = 0.25 M, T = 298 K.

With a fixed amino acid concentration of 0.02 M, the rate constant proved independent of the concentration of BrO" over the range (0.38-3.09) x 10"3M for N-Br-aminoisobutyric acid and N-Br-Proline. The plot of the obtained initial absorbance values against the initial N-Br-amino acid cone tration shows that Beer s law is obeyed, and the values for the molar absorptivity of the studied N-bromoamino acids are listed in Table 2. 

It should be noted that the absence of a proton in the a position in the case of N-Br-aminoisobutyric acid makes unoperative its decomposition to form an a-ketoacid, and the slight increase in the observed reaction rate constant upon increasing the NaOH concentration can be attributed to a secondary decomposition process, probably leading to the formation of an hydrazine (refs. 22 - 24). 

Influence of ionic strength on the reaction rate constant. The influence of the ionic strength on the reaction rate constant was studied using KCl as electrolyte. The results obtained in this study are listed in Table 4, where we can see that the reaction rate constant for N-Br-alanine decomposition undergoes an increment of 40 % upon changing the ionic strength from 0.27M to IM, while in the case of N-Bromoaminoisobutyric acid the increment of the reaction rate constant is of about 12 %. This is an evidence of a non ionic mechanism in the case of the decomposition of N-Br-aminoisobutyric acid, as it is expected for a concerted decarboxylation mechanism. For the decomposition of N-Br-proline the increase on the reaction rate constant is about 23 % approximately, an intermediate value. This is due to the fact both paths (concerted decarboxylation and elimination) have an important contribution to the total decomposition process. 

Amino acid abbreviations aa, generic amino acid Ala, L-alanine Aib, 2-aminoisobutyric acid Cys, L-cysteine Asp, L-aspartic acid Glu, L-glutamic acid Gly, glycine Lys, L-ly-sine Ser, L-serine Trp, L-tryptophan Ser, 2-amino-3-(5-methyl-2,4-dioxo-3,4-dihydro-2H-... 

P-aminoisobutyrate are elevated in the rare metabohc disorder hyperbeta-alaninemia. 

Unlike the end products of purine catabolism, those of pyrimidine catabolism are highly water-soluble COj, NH3, P-alanine, and P-aminoisobutyrate (Figure 34-9). Excretion of P-aminoisobutyrate increases in leukemia and severe x-ray radiation exposure due to increased destruction of DNA. However, many persons of Chinese or Japanese ancestry routinely excrete P-aminoisobutyrate. Humans probably transaminate P-aminoisobutyrate to methylmalonate semialdehyde, which then forms succinyl-CoA (Figure 19-2). 

Farkas WR, Fischbein A, Solomon S, et al. 1987. Elevated urinary excretion of beta-aminoisobutyric acid and exposure to inorganic lead. Arch Environ Health 42 96-99. 

The analysis of extraterrestrial matter is concentrated on the detection of nucleic acid and protein building blocks, i.e., N-heterocycles and amino acids. The search for such compounds began immediately after the fall of the Murchison meteorite. Twenty-two amino acids were detected in it as early as 1974 eight of them pro-teinogenic, ten which hardly ever occurred in biological material, and four which were unknown in the biosphere. Up to now, about 70 amino acids have been identified (Cronin, 1998), the most common being glycine and a-aminoisobutyric acid. The latter is a branched-chain amino acid with the smallest possible number of carbon atoms. The most frequently found amino acids occur in concentrations of... 

The number of scientific articles published on meteorites has increased dramatically in the last few years few of these, however, concern themselves with small meteorites, the size of which lies between that of the normal meteorites (from centimetres to metres in size) and that of interplanetary dust particles. In the course of an Antarctic expedition, scientists (mainly from French institutions) collected micrometeorites from 100 tons of Antarctic blue ice (Maurette et al 1991). These micrometeorites were only 100 400 pm in size five samples, each consisting of 30-35 particles, were studied to determine the amount of the extraterrestrial amino acids a-aminoisobutyric acid (AIBS) and isovaline—both of which are extremely rare on Earth—which they contained. The analysis was carried out using a well-tested and extremely sensitive HPLC system at the Scripps Institute, La Jolla. Although the micrometeorites came from an extremely clean environment, the samples must have been contaminated, as they all showed traces of L-amino acids. Only one sample showed a significantly higher concentration of AIBS (about 280 ppm). The AIBS/isovaline ratio in the samples also lay considerably above that previously found in CM-chondrites. 

A ngstrom unit (ICE10 m) adenosine diphosphate N-(2-aminoethyl)-glycine a-aminoisobutyric acid residues adenosine monophosphate amidotriphosphate adenosine triphosphate... 

Barone, V., F. Fratemali, and P. L. Cristinziano. 1990. Sensitivity of Peptide Conformation to Methods and Geometrical Parameters. A Comparative Ab Initio and Molecular Mechanics Study of Oligomers of a-Aminoisobutyric Acid. Macromolecules 23, 2038-2044. 

Aminoisobutanol, a216 2-Aminoisobutyric acid, a217 5-Aminoisophthalic acid, a 14... 

Using the Multipin method, Gilbertson then synthesized 27 undecapeptides on solid phase, which were presumed to have a helical conformation. This was induced by frequent use of the a-alkylated amino acid aminoisobutyric acid. The phosphine-thiooxide-containing residues were positioned in the i and i + 4 positions, which would lead to the two phosphines being adjacent in the helical peptide chain. In addition, Gilbertson synthesized 36 peptides containing phosphines in the i and i + 1 positions. 

VV Suresh Babu, HN Gopi. Rapid and efficient synthesis of peptide fragments containing a-aminoisobutyric acid using Fmoc-amino acid chlorides/potassium salt of 1-hydroxybenzotriazole. Tetrahedron Lett 39, 1049, 1998. 

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