DL-Serine

Enzymatic Process. Chemically synthesized substrates can be converted to the corresponding amino acids by the catalytic action of an enzyme or the microbial cells as an enzyme source, t - Alanine production from L-aspartic acid, L-aspartic acid production from fumaric acid, L-cysteine production from DL-2-aminothiazoline-4-catboxyhc acid, D-phenylglycine (and D-/> -hydtoxyphenylglycine) production from DL-phenyUiydantoin (and DL-/)-hydroxyphenylhydantoin), and L-tryptophan production from indole and DL-serine have been in operation as commercial processes. Some of the other processes shown in Table 10 are at a technical level high enough to be useful for commercial production (24). Representative chemical reactions used ia the enzymatic process are shown ia Figure 6. 

Chemical Name DL-serine 2-[(2,3,4-trihvdroxvphenyl)methvl] hydrazide Common Name —... 

C) dl-Serine.—One-half (350-375 g.) of the crude bromo-methoxypropionic acid prepared from the saponification of 800 g. of methyl a-bromo-/3-methoxypropionate is heated with 3.5 1. of concentrated ammonium hydroxide in a glass-lined autoclave (Note T4) for ten to fifteen hours at 90-100°, and the solution from the bomb is concentrated to a thick syrup under reduced pressure (Note 15). Two liters of water is added, and the solution is concentrated to dryness. The cake is dissolved in 1.5 1. of 48 per cent hydrobromic acid and refluxed for two and one-half hours. The resulting dark solution is concentrated to a volume of about 500 cc. and then cooled under the tap. The... 

FIGURE 11 Effect of the concentrations of organic modifiers in TLC (a) of acetonitrile on the chiral resolution of dansyl-DL-serine, (O) D- and ( ) L-enantiomers (from Ref. 101), and (b) of methanol on the chiral resolution of RS-aminoglutethimide (from Ref. 103). 

Nohira, H. and Kurogami, S. (1983) Optical resolution of DL-serine, Jpn. Kokai Tokkyo Koho JP58-180464 Chem. Abstr. 100 121616 (1984). 

Chemical Name DL-Serine 2-[(2,3,4-trihydroxyphenyl)methyl]hydrazide Common Name -Structural Formula ... 

Fig. 9.7 Effects of /3-phenyl-DL-serine, L-threonine and a-methyl-DL-serine on absorption (A) and CD (B) spectra of tryptophanase in 100 mM potassium phosphate buffer, pH 7.8, containing 2 mM dithiothreitol and 2mM EDTA. Protein concentration 1.8 mg/ml. Curve 1, unliganded enzyme. Curve 2, same as 1 + 15 mM /3-phenyl-ni -serine (threo form). Curve 3, same as 1 + 165 mM L-threonine. Curve 4, same as 1 + 500 mM a-methyl-DL-serine. (Reproduced with permission from Zakomirdina el al., Biochimie., 71, 548 549 (1989)).

It has been found68-70 that the reaction of tryptophanase with the inhibitory amino acids, /3-phenyl-DL-serine (threo form), L-threonine and D-alanine, is accompanied by a manifold increase in the reduced LD, i.e. in the ratio of LD to absorbance (AA / A) in the 420-425 nm band (Fig. 9.12 Table 9.2). This band belongs to the protonated internal PLP-lysine... 

DL-Serine occurs as white crystals or crystalline powder. It is soluble in water, but insoluble in alcohol and in ether. It melts with decomposition at about 246° using a closed capillary tube and a bath preheated to 225°. It is optically inactive. 

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