Pyruvic dimethyl

Acid moieties include formic acid itself, formates and orthoesters, formamide, DMF dimethyl acetal and ethyl diethoxyacetate, acids, acid chlorides and anhydrides, the last including a rare [3,4-oxalate esters, 2-acyl or 2-ethoxycar-bonyl derivatives e.g. 180) are formed. 

Lubineau and coworkers [18] have shown that glyoxal 8 (Ri = R2 = H), glyoxylic acid 8 (Ri = H, R2 = OH), pyruvic acid 8 (Ri = Me, R2 = OH) and pyruvaldehyde 8 (Ri = H, R2 = Me) give Diels-Alder reactions in water with poor reactive dienes, although these dienophiles are, for the most part, in the hydrated form. Scheme 6.6 illustrates the reactions with (E)-1,3-dimethyl-butadiene. The reaction yields are generally good and the ratio of adducts 9 and 10 reflects the thermodynamic control of the reaction. In organic solvent, the reaction is kinetically controlled and the diastereoselectivity is reversed. 

Variety of a-keto esters, such as methyl and ethyl pyruvate, methyl mandalate, dihydro-4,4 - dimethyl-2,3 fiiranedione were used to calculate the shielded form of [CDdosed - a-keto ester] complexes leading to the formation of ( R) or (S) product, respectively. The details of these results will be a subject of a subsequent paper [17]. As emerges from these calculations the favourable directionality is maintained in complexes (R), even for dihydro-4,4 - dimethyl-2,3 fiiranedione. 

Recently, platinum nanoparticles protected by N,N-dimethyl-N-cetyl-N-(2-hydro-xyethyl)ammonium chloride salt and modified with cinchonidine were investigated in the enantiomeric hydrogenation of ethyl pyruvate in pure biphasic liquid-liquid (water/substrate) media at room temperature [139]. For the first time, the aqueous phase containing Pt(0) nanocatalysts with an average size of 2.5 nm could be reused for successive hydrogenations, and with a total conversion of activity and enantioselectivity in (R)-(+)-ethyl lactate up to 55% (Scheme 9.12). 

Salzer et al. prepared a set of planar-chiral diphosphine ligands based on the arene chromium tricarbonyl backbone (Fig. 36.3) [21]. The straightforward four-step synthetic route allowed the preparation of 20 ligands of this family. These ligands were tested in Ru- and Rh-catalyzed enantioselective hydrogenation of various substrates, including the standard C=C substrates (dimethyl itaconate, methyl-2-acetamidocinnamate, methyl-2-acetamidoacrylate) as well as MEA-imine (l-(methoxymethyl)ethylidene-methylethylaniline) and ethyl pyruvate. Moderate conversions and ee-values were obtained. 

A different approach is the combination of a Pt-carbonyl-cluster with a special dye, Safranine O (Saf 3,7-diamino-2,8-dimethyl-5-phenylphenazinium) in an aqueous/organic two-phase system [48]. The dye is reduced in the organic phase and subsequently, in a type of phase-transfer catalysis, it reduced the cofactor in the aqueous phase. In this example l-LDH is used as a production enzyme, reducing pyruvate to L-lactate (Scheme 43.6). Complete conversion was obtained within 48 h, the mixture containing pyruvate, NAD+ and the Pt-cluster catalyst in a 600 10 1 molar ratio. The TOF for NAD+ was 15 h-1. 

Rhodium and iridium nanoparhcles entrapped in aluminum oxyhydroxide nanofibers were shown by Park et al. to be suitable catalysts for the hydrogenation of arenes and ketones at room temperature, with hydrogen at ambient pressure [103]. Rhodium in aluminum oxyhydroxide [Rh/A10(0H)] and iridium in aluminum oxyhydroxide [Ir/A10(0H)], were simply prepared from readily available reagents such as RhCls and IrCls hydrates, 2-butanol and Al(O-sec-Bu) at 100°C. Substrates such as cyclopentanone, 2-heptanone, ethyl pyruvate, acetone and 2,6-dimethyl-4-heptanone were reduced to the corresponding alcohols either in n-hexane at room temperature (maximum TOF 99 h" for ethyl pyruvate) or in solventless conditions at 75 °C using 4 atm of H2 (maximum TOF 660h" for acetone, 330 for 2-heptanone). 

A hypothetical biosynthetic sequence has been proposed for the 3-alkyl-2,6-dimethylpyrazines (482) from various species of Odontomachus ants, as shown in Scheme 65. The acyloin (507), prepared by condensation of the pyruvate with active acetate, or the derived dione (508) may condense with the amide (509) of alanine, ultimately giving the 3-alkyl-2,6-dimethylpyrazines (482) (141). A separate biogenesis is envisaged for the 3-alkyl-2,5-dimethylpyrazines (481) such as 3-isopentyl-2,5-dimethyl (20h) and 2,5-dimethyl-3-styrylpyrazines (20j,... 

A recent synthesis of 1 by Ganem et al.2 uses dimethyl diazomalonate for introduction of the enol pyruvate side chain. 

A model system demonstrating the nutritional destruction of lysine in bovine plasma albumin (BPA) by reaction with either a dialdehyde (MA) or a keto-aldehyde (MGA) was studied in relation to reaction rates as affected by pH, temperature, reaction time and carbonyl concentration. The BPA was Fraction V obtained from Schwartz/Mann and had a molecular weight of 69 x 103 with sixty lysine residules/mole, an assayed content of 11.4%. It was dissolved in 0.0200 M phosphate-citrate buffer adjusted to the desired pH. Malonaldehyde was prepared by acid hydrolysis of its bis-(dimethyl acetal). An aqueous solution of pyruvic aldehyde was diluted with distilled water and phosphate-citrate buffer to give an MGA solution of the desired pH (16). 

Thermolysis of 2-acetoxy-2-methoxy-5,5-dimethyl-A3-l,3,4-oxadiazoline affords acetoxy(methoxy) carbene.60 The thermal rearrangement of acetoxy(methoxy) car-bene to methyl pyruvate was studied by DFT at the B3PW91/6-31G(d,p) level. The conformation of the carbene was considered, as were competing fragmentations to radical pairs. The authors concluded that the reaction is a concerted 1,2-migration rather than a fragmentation-recombination process. 

Similar product ratios were reported for the methyl pyruvate/2,3-dimethyl-2-butene photoreaction. In this case, however, a state selectivity effect is responsible for the formation of the different ether and alcohol products [31]. Obviously the existence of allylic hydrogens favors the formation of unsaturated acyclic products via hydrogen migration steps at... 

In 1957, Breslow (13) showed that the hydrogen atom in the 2-position of the thiazolium-ion portion of thiamin is ionized readily the electronic structure of the anion imitates that of cyanide ion. The chemistry of thiamin can then be explained the decarboxylation of pyruvate and the acetoin condensation are processes that follow conventional mechanisms in modern language, thiamin allows an acyl group to become an anion equivalent. Subsequent to Breslow s initial discovery, he and McNelis (14) synthesized 3,4-dimethyl-2-acetylthiazolium ion, and showed that in fact it is hydrolyzed rapidly. 

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