L-2-aminobutyric acid

An alternative method of synthesis consists of preparing (+) 2-aminobutanol (34.1.3) by redncing ethyl ester of L-2-aminobutyric acid hydrochloride with hydrogen nsing simnlta-neonsly Raney nickel and platinum oxide catalysts. This gives pure (+) 2-aminobutanol. Reacting this with 1,2-dichloroethane in the presence of sodium hydroxide gives the desired ethambutol (34.1.4) [16,17]. 

Examples of uimatural L-amino acids that can be accessed by transaminase methodology are L-2-aminobutyric acid, i.-homophcnylalaninc, and L-lert-leu-cine the latter is not accessible by an asymmetric hydrogenation approach because of the absence of a P-hydrogen. 

Some of the modules in LPS1 recognize alternative substrates supplied in vitro (Riederer et al., 1996). For example, L-2-aminobutyric acid or L-valine... 

In the oxidative deamination reaction, the enzyme was active toward N-[l-D-(carboxyl)ethyl]-L-methionine, N-[l-D-(carboxyl)ethyl]-L-phenylalanine, etc. The substrate specificity for amino donors of ODH in the reductive secondary amine-forming reaction was examined with pyruvate as a fixed amino acceptor [15,24]. The enzyme utilized L-norvaline, L-2-aminobutyric acid, L-norleucine, P-chloro-L-alanine, o-acetyl-L-serine, L-methionine, L-isoleucine, L-valine, L-phenylalanine, L-homophenylalanine, L-leucine, L-alanine, etc. 3-Aminobutyric acid and L-phenylalaninol also acted as substrates for the enzyme. Other amino compounds, such as P-amino acids, amino acid esters and amides, amino alcohols, organic amines, hydroxylamines, and hydrazines, were inactive as substrates. Pyruvate, oxaloacetate, glyoxylate, and a-ketobutyrate were good amino acceptors. We named the enzyme as opine... 

Ergo Stine Et L-2-aminobutyric acid CHjPh L-phenylalanine... 

L 2 aminobutyric acid can substitute for L-alanine (CyV). N-Methyl-L-leucine in position 4 may be replaced by N-methyl-L isoleucine (Cy29) or by L-valine in CyQ and CyS. Regarding possible biosynthetic pathways, variations at position 1 are of special interest CyF and CyK contain deoxy-MeBmt, whereas N-methyl-L-Z-amino-octanoic acid is found in CyZ, Both building units probably stem from a common precursor of the genuine amino acid (4R) 4 l E) 2 butenyI] 4 fnethYl L-threonine (Bmt). A full exchange of this characteristic structural unit by N-methyl-L-leucine is observed in CyO. At present, positions 3 and 8 containing sarcosine and D-alanine, respectively, are the only conserved building units. 

NMR analysis of the four differently X2-labeled CyA samples, as exemplified in Figure 3 for [1-i Cj- and [6- C]glucose, it was concluded that L-2-aminobutyric acid originates... 

Figure 4.7 Chemical structures of the amino acids L- //o-isoleucine (L-aiLe), D-leucine (D-Leu), L-norvaline (L-Nva), D-methionine (D-Met), L-2-aminobutyric acid (L-Abu) and D-norleucine (D-Nle).

Screening for novel biocatalyst also afforded some interesting synthetic approaches to this challenging goal. A PLP-dependent a-methylserine aldolase from different microorganisms [190, 191] was uncovered to catalyze the addition of L-alanine and L-2-aminobutyric acid to formaldehyde (Scheme 10.25), which resulted in the stereoselective formation of a quaternary C-center, rather unprecedented for naturally occurring aldolase. The enzyme from Ralstonia sp. Strain AJ110405 was applied in a whole-cell catalyzed stereospecific synthesis of a-methyl-L-serine [190]. 

Amino acids L-2-Aminobutyric acid co-TA V. fluvialis) 2-Oxobutyric acid + benzylamine AS [46]... 

For the synthesis of L-2-aminobutyric acid, the -transaminase from Vibrio flu-vialis with 2-oxobutyric acid and benzylamine as substrates was established [46]. 

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