Acyl uniqueness

The reverse reaction is an intramolecular acidolysis of amide group by the o-carboxyhc acid to reform anhydride and amine. This unique feature is the result of an ortho neighboring effect. In contrast, the acylation of an amine with ben2oic anhydride is an irreversible reaction under the same reaction conditions. The poly(amic acid) stmcture (8) can be considered as a class of polyamides. Aromatic polyamides that lack ortho carboxylic groups are very... 

Reaction 3 is analogous to the dehydrogenation of fatty acyl-CoA thioesters (see Figure 22—3). In isovaleric acidemia, ingestion of protein-rich foods elevates isovalerate, the deacylation product of isovaleryl-CoA. Figures 30-20, 30-21, and 30-22 illustrate the subsequent reactions unique to each amino acid skeleton. 

We have also recently observed a unique example of an aryl to acyl migration (Scheme 30).26 In this case, the intermediate is easily trapped by running the reaction in an alcohol solvent to form the carbamate. 

The most striking feature of these results is the orientation of the unique 13C hyperfine matrix axes, relative to those of the 57Fe hyperfine axes. This orientation led Fairhurst et al.41 to assign the spectrum to [Fe(CO)5] (2) and to describe the species as a substituted acyl radical. However, these authors did not discuss the orientation of the g-matrix axes. The y-axis, normal to the reflection plane, is common to all three matrices. The x- and z-axes of the g-matrix, however, are oriented about 21° away from the corresponding 57Fe hyperfine matrix axes. Since the iron d-orbital contribution to the SOMO appears to be nearly pure dz2, the 57Fe hyperfine matrix major axis must correspond to the local z-axis, assumed to be essentially the Fe-C bond. Thus we must ask Why are the g-matrix axes different The SOMO can be written ... 

The method (i) can be applied to the synthesis of almost all heavy ketones (Tables 3-5). Silanethiones and a silaneselone stabilized by the coordination of a nitrogen group have been synthesized by the method (ii) (Table 4). The method (iii) is effective to the synthesis of kinetically stabilized tricoordinate heavy ketones, although it cannot be applied to the synthesis of double-bond compounds between heavier group 14 elements and tellurium due to the instability of polytellurides (Table 3). The method (iv) can be used only when the unique dilithiometallanes can be generated (Table 3). The synthesis of heavy ketones by the method (v) demands the isolation of the corresponding heavy acyl chlorides as stable compounds (Table 5). 

Conjugation between the imino and acyl [121], or nitrile (in complex 1.47) [122] moieties permitted the remote activation of nickel. Another catalyst (1.48) exhibiting coordination via an alkenyl moiety is noteworthy because of its sterically small size, which should prohibit the production of high molecular weight polymers [123], This is believed to be possible because of the catalyst s unique electronic properties. As bulkier imino-aryl substituents are introduced, polymerization activity and polymer molecular weight increases, as expected [124],... 

The purpose of this article is to review recent results on the carbonylation chemistry of actinide-to-carbon sigma bonds, bearing in mind the unique properties of 5f-organometallics cited above. We focus our attention on the properties of bis(pentamethylcyclopentadienyl) actinide acyls. Just as transition metal acyls (A) occupy a pivotal role in classical carbonylation chemistry, it will be seen that many of the unusual... 

A few enzymes, such as the previously mentioned CNP, are believed to be fairly specific for myelin/oligodendro-cytes. There is much more in the CNS than in peripheral nerve, suggesting some function more specialized to the CNS. In addition, a unique pH 7.2 cholesterol ester hydrolase is also enriched in myelin. On the other hand, there are many enzymes that are not myelin-specific but appear to be intrinsic to myelin and not contaminants. These include cAMP-stimulated kinase, calcium/calmodulin-dependent kinase, protein kinase C, a neutral protease activity and phosphoprotein phosphatases. The protein kinase C and phosphatase activities are presumed to be responsible for the rapid turnover of MBP phosphate groups, and the PLP acylation enzyme activity is also intrinsic to myelin. 

In a recent report [67], the spirocyclopropyloxy structural motif was incorporated in sulbactam, and the compounds 12a and 12b had good activity against various -lactamases. The mechanism of inhibition of /3-lactamase by 12a or 12b is unique. After the initial acylation, the cyclopropyloxy group can promote the subsequent chemical events to form the aldehyde or the oxycar-benium moiety for further cross-linking with other active site residues of the enzyme (Scheme 5). 

In contrast to pheromones that involve single complex compounds, many moth species have been found to utilize a specific blend of relatively simple fatty acid-derived compounds. It appears that the evolution of a unique enzyme, A1 desaturase, used in combination with 2-carbon chain-shortening reactions (Figure 3) has allowed moth species to produce a variety of unsaturated acetates, aldehydes, and alcohols that can be combined in almost unlimited blends to impart species specificity. For example, biosynthetic precursors for the six-component pheromone blend of acetates for the cabbage looper moth (12) (Figure 2) can be determined easily from the cascade of acyl intermediates produced by the A11-desaturase and chain-shortening reactions (Figure 3). 

Acyl azides (see Section 2.13) The acyl-azide method of coupling is unique for two reasons. First, it is the only case in which the immediate precursor of the activated form of the peptide is not the parent acid. The starting material is the peptide ester that is obtained from the amino acid ester by usual chain assembly (Figure 2.25, path A). Second, it is the only method that just about guarantees production of a peptide that is enantiomerically pure, provided scrupulous attention is paid to details of procedure. There is no danger for loss of chirality during conversion of the ester to the hydrazide and then the azide, but care must be taken to avoid contact of... 

Acyl glucuronides (i.e., ester glucuronides of general structure 11.6) are formed as conjugates of carboxylic acids. These compounds are rather uniquely reactive a) they are far more sensitive to chemical hydrolysis than ether... 

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