Propionic generation from acetic acid

Succinyl-CoA derived from propionyl-CoA can enter the TCA cycle. Oxidation of succinate to oxaloacetate provides a substrate for glucose synthesis. Thus, although the acetate units produced in /3-oxidation cannot be utilized in glu-coneogenesis by animals, the occasional propionate produced from oxidation of odd-carbon fatty acids can be used for sugar synthesis. Alternatively, succinate introduced to the TCA cycle from odd-carbon fatty acid oxidation may be oxidized to COg. However, all of the 4-carbon intermediates in the TCA cycle are regenerated in the cycle and thus should be viewed as catalytic species. Net consumption of succinyl-CoA thus does not occur directly in the TCA cycle. Rather, the succinyl-CoA generated from /3-oxidation of odd-carbon fatty acids must be converted to pyruvate and then to acetyl-CoA (which is completely oxidized in the TCA cycle). To follow this latter route, succinyl-CoA entering the TCA cycle must be first converted to malate in the usual way, and then transported from the mitochondrial matrix to the cytosol, where it is oxida-... 

Silyloxy)alkenes were first reported by Mukaiyama as the requisite latent enolate equivalent to react with aldehydes in the presence of Lewis acid activators. This process is now referred to as the Mukaiyama aldol reaction (Scheme 3-12). In the presence of Lewis acid, anti-aldol condensation products can be obtained in most cases via the reaction of aldehydes and silyl ketene acetals generated from propionates under kinetic control. 

Type iii-b This reaction leads to products (67). The electrochemical oxidation of the sodium salts of acetic, propionic, and isovaleric acids in the presence of ethylenic compounds bearing electron-withdrawing substituents gives 1,2-dialkylated adducts as the main products. A methyl radical generated from an acetate ion reacts with diethyl fumarate to give diethyl 2,3-dimethylsuccinate in 80% yield [106]. 

The homolytic substitution of thiophene by electrophilic carbon radicals provides a good method for the synthesis of (2-thienyl)acetic and (2-thienyl)propionic acids. The electrophilic radical, CH2C02Et, generated from ICH2C02Et, H202 and catalytic Fe2+ in DMSO, reacts with thiophene to form (2-thienyl)acetic ester in 62% yield (92JOC6817). 

Challenging the dynamic thiolester system CDS-1B with acetylcholinesterase resulted in similar product formations, but a slightly slower enzyme resolution process, than CDS-1A due to the larger size of CDS-1B. To probe the effect of the thiol moiety, dynamic thiolester systems, using only one thiol per system, were furthermore generated and applied to the enzyme resolution process. Thus, the additional CDS-1B, 1C, ID, and IE were prepared with equimolar amounts of five thiolesters 1A-E and one equivalent of either thiol 2, 8,10, or 12 (Table 1). These systems contained ten thiolesters and two thiols. Challenging these systems with acetylcholinesterase resulted in half-lives of formation of the different hydrolysis products, acetic, propionic, and butyric acids, as shown in Table 1. These results indicate that only CDS-1 A (Table 1, Entry 2), generated from five thiolesters 1A-E... 

Acetic acid decomposed on the (114[-faceted of the TiOi (001) surface to produce ketene as well as acetone [44]. The acetone generated arose from bimolecular coupling of pairs of surface acetates at four-fold coordinate cations this is analogous to the production of formaldehyde from surface formate on identically prepared surfaces. The reaction of propionic acid corresponded directly to the reaction of acetic acid, producing methyl ketene and 3-pentanone [46]. 

Table 3. Experimental conditions and the weight percent of original organic matter converted to acetic, propionic, butyric, and valeric acids at the maximum for acetic acid generation from organic matter in samples of whole rock (WR), solvent-extracted rock (ER) and isolated kerogen (IK)... 

The Ireland-Claisen reaction of ( )-vinylsilanes has been applied to the stereoselective synthesis of syn- and c/nti-2-substituted 3-silyl alkcnoic acids. a R-2-Alkyl-3-silyl acids are prepared by rearrangement of ( )-silyl ketene acetals which are generated in situ from the kinetically formed (Z)-enolate of the corresponding propionate ester40. Chelation directs the stereochemistry of enolization of heteroelement-substituted acetates in such a way that the syn-diastereomers are invariably formed on rearrangement403. 

Since dienolates 1 and 2 represent diacetate synthons, the dienolate derived from 6-ethyl-2,2-dimethyldioxinone can be seen as a propionate-acetate syn-thon. The synthesis of the corresponding dienolate provides a mixture of the E and Z enolates in a 3 5 ratio. The reaction with Ti-BINOL complex 5 generates a 5 1 mixture with the syn isomer as the major diastereomer. After separation of the diastereomers, the enantiomeric excess of the syn isomer was determined to be 100%. The anti isomer was formed in 26% ee. The same transformation performed with boron Lewis acid 7 gave the anti isomer as the major compound, but only with 63% ee. The minor syn isomer was produced with 80% ee. The observed selectivity could be rationalized by an open transition state in which minimization of steric hindrance favors transition state C (Fig. 1). In all three... 

Aldol Addition. A catalyst generated upon treatment of Cu(OTf)2 with the (5,5)-r-Bu-box ligand has been shown to be an effective Lewis acid for the enantioselective Mukaiyama aldol reaction. The addition of substituted and unsubstituted enolsilanes at -78 °C in the presence of 5 mol % catalyst was reported to be very general for various nucleophiles, including silyl dienolates and enol silanes prepared from butyrolactone as well as acetate and propionate esters. 

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