Ketonic carbonyl groups

Like aldehydes ketone functions take precedence over alcohol functions double bonds halogens and alkyl groups m determining the parent name and direction of numbering Aldehydes outrank ketones however and a compound that contains both an aldehyde and a ketone carbonyl group is named as an aldehyde In such cases the carbonyl oxy gen of the ketone is considered an 0x0 substituent on the mam chain... 

The systematic lUPAC name of ethyl acetoacetate is ethyl 3 oxobutanoate The presence of a ketone carbonyl group is indicated by the designation oxo along with the appro priate locant Thus there are four carbon atoms m the acyl group of ethyl 3 oxobutanoate C 3 being the carbonyl carbon of the ketone function... 

Ammonia reacts with the ketone carbonyl group to give an mine (C=NH) which is then reduced to the amine function of the a ammo acid Both mine formation and reduc tion are enzyme catalyzed The reduced form of nicotinamide adenine diphosphonu cleotide (NADPH) is a coenzyme and acts as a reducing agent The step m which the mine is reduced is the one m which the chirality center is introduced and gives only L glutamic acid... 

Ketose (Section 25 1) A carbohydrate that contains a ketone carbonyl group in its open chain form Kiliam-Fischer synthesis (Section 25 20) A synthetic method for carbohydrate chain extension The new carbon-carbon bond IS formed by converting an aldose to its cyanohydnn Reduction of the cyano group to an aldehyde function com pletes the synthesis... 

In Example 1 the solute, acetone, contains a ketone carbonyl group which is a hydrogen acceptor, i.e., solute class 5 according to Table 15-4. This solute is to be extracted from water with chloroform solvent which contains a hydrogen donor group, i.e., solvent class 4. The solute class 5 and solvent class 4 interaction in Table 15-4 is shown to give a negative deviation from Raonlt s law. 

Ketonic carbonyl groups are commonly encountered in steroids and their reduction is facile, even in the absence of an alcohol. The lithium-ammonia reduction of androsta-l,4-diene-3,17-dione affords androst-4-ene-3,17-dione in 20% yield but concurrent reduction of the C-17 ketone results in formation of testosterone in 40% yield, even though the reduction is performed rapidly at —40 to —60° and excess lithium is destroyed with solid ammonium chloride. Similar reduction of the C-17 carbonyl group has been observed in other compounds. In the presence of an alcohol, a ketone is complete-... 

Ketose (Section 25.1) A carbohydrate that contains a ketone carbonyl group in its open-chain form. 

A histidine deprotonates the acetyl-CoA enol, which adds to the ketone carbonyl group of oxaloacetate in an aldol-like reaction. Simultaneously, an acid N-H proton of another histidine protonates the carbonyl oxygen, producing (S)-citryl CoA. 

Look at the side chains of the 20 amino acids in Table 26.1, and then think about what is not present. None of the 20 contain either an aldehyde or a ketone carbonyl group, for instance. Is this just one of nature s oversights, or is there a likely chemical reason What complications might an aldehyde or ketone carbonyl group cause ... 

Steps 6-8 of Figure 29.5 Reduction and Dehydration The ketone carbonyl group in acetoacetyl ACP is next reduced to the alcohol /S-hydroxybutyry] ACP by yS-keto thioester reductase and NADPH, a reducing coenzyme closely related to NADH. R Stereochemistry results at the newly formed chirality center in the /3-hydroxy thioester product. (Note that the systematic name of a butyryl group is biitanoyl.)... 

Note that the hydroxyl-bearing carbon of citrate is a prochirality center and contains two identical "arms." Because the initial aldol reaction of acetyl CoA to oxaloacetate occurs specifically from the Si face of the ketone carbonyl group, the pro-S arm of citrate is derived from acetyl CoA and the pro-R arm is derived from oxaloacetate. 

Step 3 of Figure 29.12 Oxidation and Decarboxylation (2K,3S)-lsocitrate, a secondary alcohol, is oxidized by NAD+ in step 3 to give the ketone oxalosuccinate, which loses C02 to givea-ketoglutarate. Catalyzed by isocitrate dehydrogenase, the decarboxylation is a typical reaction of a /3-keto acid, just like that in the acetoacetic ester synthesis (Section 22.7). The enzyme requires a divalent cation as cofactor, presumably to polarize the ketone carbonyl group. 

Concealed within spirocyclic intermediate 16 are rings B and F of ginkgolide B. Intermediate 16 is readily formed in two steps from a readily available starting material and it contains a strategically placed ketone carbonyl group which provides several options for further advance. A particularly straightforward route to 15 includes the conversion of ketone 16 into enol triflate 21 by means of McMurry s protocol.16 Thus, enolization of 16 with LDA in dimethoxyethane at -78 °C followed by triflation of the enolate oxygen atom with /V-phenyltrifluoromethanesulfonimide furnishes enol triflate 21 in a yield of 80%. 

Other compounds with reactive methylene and methyl groups are completely analogous to the nitroalkanes. Compounds with ketonic carbonyl groups are the most important. Their simplest representatives, formaldehyde and acetone, were considered for many decades to be unreactive with diazonium ions until Allan and Podstata (1960) demonstrated that acetone does react. Its reactivity is much lower, however, than that of 2-nitropropane, as seen from the extremely low enolization equilibrium constant of acetone ( E = 0.9 x 10-7, Guthrie and Cullimore, 1979 Guthrie, 1979) and its low CH acidity (pK = 19.1 0.5, Guthrie et al., 1982). ... 

Monosaccharides with an aldehydic carbonyl or potential aldehydic carbonyl group are called aldoses those with a ketonic carbonyl or potential ketonic carbonyl group, ketoses. 

Monosaccharides containing two (potential) ketonic carbonyl groups are termed diketoses (see 2-Carb-l 1). 

The most senior of other functional groups expressed in the suffix receives the lowest possible locant, i.e. carboxylic acid (derivatives) > (potential) ketonic carbonyl groups. 

Names of individual ketoaldonic acids are formed by replacing the ending -ulose of the corresponding ketose by -ulosonic acid , preceded by the locant of the ketonic carbonyl group. The anion takes the ending -ulosonate . The numbering starts at the carboxy group. 

The combination of thionation by Lawesson s reagent [98] of oxoenamino-ketones 96 with normal electron-demand Diels-Alder reaction of conjugated aldehydes allows a variety of thiopyrans 97 to be synthesized by a regio-selective and chemoselective one-pot methodology [99] (Equation 2.28). Thionation occurred at the more electrophilic ketonic carbonyl group. O O... 

A more highly oxidized indole relative is isatin (47). The ketonic carbonyl group is nonenolizable and has interesting properties. In strong acid it... 

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