Lactic acid from alanine

A pH-dependent chemoselective catalytic reductive amination of a-keto acids, affording a-amino acids with HCOONH4 in water, was achieved using the complex 31 or its precursor 28 as the catalyst [51]. The formation rates of alanine and lactic acid from pyruvic acid exhibited a maximum value around pH 5 and pH 3, respectively, and therefore, alanine was obtained quite selectively (96%) with a small amount of lactic acid (4%) at pH 5 (Scheme 5.18). A variety of nonpolar, uncharged polar and charged polar amino acids were also synthesized in high yields. 

The second approach is to look for a suitable naturally occurring compound with a three carbon chain and a chirality centre as the starting material. The obvious candidates are lactic acid and alanine or one of their derivatives. The scheme shown on the right outlines two of the possible synthetic routes starting from (S)-lactic acid ethyl ester, which is both cheap and... 

Chiral dioxolanone 71 and oxazolidinone 72 alkenes, which can be readily prepared from lactic acid or alanine, respectively, undergo diastereoselective radical... 

Scheme 4.22 Synthesis of lactic acid or alanine starting from vinyl chloride via a hydroformylation step.

Racemic dinitropyridyl, dinitrophenyl, and dinitrobenzoyl amino acids were resolved on C-18W/UV TLC and HPTLC plates (Macherey-Nagel) developed with 2% aqueous isopropanol containing 2-5% BSA. Development times were 1-2 h, and visualization was under 254 nm UV hght. Ri differences ranged from 0.06 to 0.49 [34]. The same plates with mobile phases composed of isopropanol -E BSA-E sodium tetraborate, acetic acid, or sodium carbonate served to separate enantiomeric D,L-methylthiohydantoin andphenylthiohydantoin derivatives of amino acids, kynureyne, 3-(l-naphthyl)alanine, lactic acid derivatives, alanine and leucine p-nitroanilides, and 2,2,2-trifluoro-l-(9-anthryl)ethanol [35], and with mobile phases composed of water with 5-7% BSA -E 2% isopropanol to separate dansyl amino acid derivatives [36]. 

Fig. 12 A- D. Separation of a mixture of cyctochromes C from various sources in 20 pm i. d. capillary columns. (Reprinted with permission from [78]. Copyright 2000 Elsevier). Conditions A bare capillary B unetched C18 modified capillary C,D etched C18 modified capillary, total column length 50 cm, active length 25 cm, voltage 30 kV (A,B,C) and 15 kV (D), mobile phase 60 mmol/1 a-alanine and 60 mmol/1 lactic acid pH 3.7, detection at 211 nm, pressurized injection for 2 s using vacuum...

Gluconeogenesis is the de novo synthesis of glucose from none carbohydrate sources. These sources (precursors) are lactic acid, glycerol and the amino acids, especially alanine, glntamine and aspartic acid (Fignre 6.22). 

Figure 9. VCD and absorption spectra in the CH stretching region of (a) L-alanine,. l M m D2O, path length 200 and b) L-lactic acid, 2.1 A in D2O, path length 300 /rM. (Reproduced with permission from ref. 89. Copyright 1985 American Chemical Society.)...

Now let us consider the further conversion of PEP and of the triose phosphates to glucose 1-phosphate, the key intermediate in biosynthesis of other sugars and polysaccharides. The conversion of PEP to glucose 1-P represents a reversal of part of the glycolysis sequence. It is convenient to discuss this along with gluconeogenesis, the reversal of the complete glycolysis sequence from lactic acid. This is an essential part of the Cori cycle (Section F) in our own bodies, and the same process may be used to convert pyruvate derived from deamination of alanine or serine (Chapter 24) into carbohydrates. 

FIGURE 4.21 H NMR spectra (400 MHz) of time course evolution of red wine in alcoholic and malolactic fermentations for grape red must (pH 3). Peaks 1, ethanol 2, ethanol satellites 3, lactic acid 4, acetic acid 5, succinic acid 6, malic acid 7, 2,3-butanediol 8, proline 9, alanine. (From Avenoza et at, 2006.)... 

Suggest a method for the synthesis of the unnatural D enantiomer of alanine from the readily available L enantiomer of lactic acid. 

Figure 10 ITP-CZE analysis of lO il of five times diluted untreated serum. (A) ITP step in the preseparation capillary, ID 0.8 mm, LE 10mmoll HCI + j3-alanine, pH 3.3, TE lOmmoll" propionic acid. Denoted components migrating behind lactic acid are driven to the second capillary. (B) CZE step in the analytical capillary, ID 0.2mm, BGE SOmmolP propionic acid + -alanine, pH 3.8. The combination of electrolytes corresponds to the T-S-T, system as shown in Figure 6. LOD 5x10 moll ascorbate. Estimated concentration of ascorbic acid in serum 1 5.74mg in serum 2 12.15mg l (Reprinted with permission from Prochazkova A, Kfivankova L, and Bocek P (1998) Quantitative trace analysis of L-ascorbic acid in human body fluids by on-line combination of capillary isotachophoresis and zone electrophoresis. Electrophoresis, vol. 10, p. 302 Wiley-VCH.)...

C12H2ooio,MO,H O. The synthesis of alanine, C H NOS by Strecker from aldehyde ammonia, formic acid, and hydrocyanic acid, and the conversion of alanine into lactic acid by means of nitrous acid, seemed to indicate the formula C H O for lactic acid, and this was confirmed by Wurtz, who obtained it by oxidisihg propylene glycol, at the same time regarding it as dibasic (C = 12, O = 16) ... 

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