Pyruvic acid R

A specific example is the transamination of alanine (R = Me) to make pyruvic acid (R = Me) and glutamic acid (R = (CH2)2COOH). 

Fig. 22, Dehydrogenation of pyruvic acid (R = —CHg) and cx-ketoglutaric acid (R = —CHg —CHa—COOH)...

The enzyme is a single enantiomer of a chiral molecule and binds the coenzyme and substrate m such a way that hydride is transferred exclusively to the face of the carbonyl group that leads to (5) (+) lactic acid Reduction of pyruvic acid m the absence of an enzyme however say with sodium borohydride also gives lactic acid but as a racemic mixture containing equal quantities of the R and S enantiomers... 

In this scheme the reversible conversion of A to O is the reaction whose rate is to be studied, whereas the reduction of O to R is the electrode process. Scheme XIV can also represent a pseudo-first-order formation of O. A specific example is the acid-base equilibrium of pyruvic acid, shown in Scheme XV. 

Only in the case of the pyruvic acid condensation product was it possible to isolate the corresponding ethyl ester under these conditions. This, on mild hydrolysis, reverted to 1-methyl-1,2,3,4-tetrahydro-j8-carbohne-1-carboxylic acid, identical with the starting material, which therefore had the assigned structure 26 (R = CH3) and was not the SchiflF s base 25 (R = CH3). Alkaline hydrolysis of the ester was accompanied by decarboxylation. ... 

Iminium ions bearing an electron-withdrawing group bonded to the sp carbon of the iminium function are very reactive dienophiles. Thus, iminium ions 26 generated from phenylglyoxal (Scheme 6.15, R = Ph) or pyruvic aldehyde (R = Me) with methylamine hydrochloride, react with cyclopenta-diene in water at room temperature with good diastereoselectivity [25] (Scheme 6.15). If glyoxylic acid is used, the formation of iminium salt requires the free amine rather than the amine hydrochloride. 

Methyl-1,2-benzenediamine (215, R = Me) with the hydrate of 3,3,3-trifluoro-pyruvic acid gave a mixture of isomers (216, R = Me) and (217, R = Me) (dioxane, reflux, 30 min 98%) from which neither appears to have been isolated in a pure state in contrast, 4-nitro-1,2-benzenediamine (215, R = NO2) and the same synthon gave a mixture of 6-nitro- (216, R = NO2) and 7-nitro-3-trifluoromethyl-2(l//)-quinoxalinone (217, R = NO2) (dioxane, reflux, 4 h 95%), from which both isomers were isolable, albeit with... 

Some sugar residues in bacterial polysaccharides are etherified with lactic acid. The biosynthesis of these involves C)-alkylation, by reaction with enol-pyruvate phosphate, to an enol ether (34) of pyruvic acid, followed by reduction to the (R) or (5) form of the lactic acid ether (35). The enol ether may also react in a different manner, giving a cyclic acetal (36) of pyruvic acid. 

The mechanism of this elegant, surprising, and widely applicable synthesis of indole derivatives was only explained recently (R. Robinson). It must be assumed that the keto-phenylhydrazones, in tautomeric hydrazo-form, undergo a species of benzidine rearrangement which, like the latter, can often occur even in dilute acid solution, e.g. with the phenylhydrazone of pyruvic acid. 

R. Guedj, A.I. Ayi u. M. Remli, Synthesis and Properties of Monofluorinated Compounds of Biological Interest, fi-Fluoro a-Amino Acids and homologous P-Fluoro-Derivates of Pyruvic Acid, Ann. Chim. (Paris) 9, 691 (1984). 

Since fluoro-carbonyl compounds are such useful and versatile synthetic intermediates, much effort has been devoted to their preparation [124], but only in a few instances has elemental fluorine been used directly. One of the earliest successful direct fluorinations of a simple carbonyl compound was the fluorina-tion of pyruvic acid derivatives which have a high enol content (R = Aryl, Acyl) (Fig. 47) [125] in the solvent being used (mixtures of CF2C1CFC12 and acetonitrile). However, in derivatives where the enol content was low (R = Alkyl), complicated mixtures of products were obtained. 

The synthesis of 23 was known to be amazingly simple pyruvic acid 22 is mixed with ammonia The yield is low, but who minds If you must have a low-yielding step, it is a good idea to have it at the start of the synthesis to avoid the waste of materials and energy. In this case, so much is achieved that a low yield is acceptable. Esterification gave the diester 21 R = Me which could be brominated with NBS (chapter 24) and combined with Ph P to give the phosphonium salt. This is the first branch complete. 

Amino acid (alanine) H-Cjl-H HO—C Pyruvic acid, a-keto acid H-(r ho-c H... 

In most cases, the stereochemistry of the quaternary carbon atom in branched-chain carbohydrates cannot be elucidated from H-n.m.r. spectra, but 13C-chemical shifts, or long-range, 13C- H coupling-constants, may often yield valuable information.114-118 Likewise, the stereochemistry of acetal carbon atoms of benzylidene derivatives,103, 104 and of acetals derived from pyruvic acid,105,106 may be determined from l3C-chemical shifts. 

Minder et al. studied various modifiers containing a nitrogen base for the enantioselective hydrogenation of ethyl pyruvate.223,224 Up to 82% ee with (R)-l-(l-naphthyl)ethylamine and up to 75% ee with (/ )-2-( 1 -pyrrolidinyl)-1 -(1 -naphthyl)-ethanol as modifiers were achieved in the hydrogenation of ethyl pyruvate to (R)-ethyl lactate over Pt-Al203 in acetic acid. 

V. DiNinno, E. L. McCandless, and R. A. Bell, Pyruvic acid derivative of a carrageenan from a marine red algae (Petrocelis species), Carbohydr. Res., 71 (1979) Cl—C4. 

P. J. Garegg, B. Lindberg, and I. Kvamstrom, Preparation and N.M.R. studies of pyruvic acid and related acetals of pyranosides Configuration at the acetal carbon atom, Carbohydr. Res., 11 (1979) 71-78. 

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