N-Carboxylation

FIGURE 1.9 (a) Amino acids build proteins by connecting the n-carboxyl C atom of one amino acid to the n-amino N atom of the next amino acid in line, (b) Polysaccharides are built by combining the C-1 of one sugar to the C-4 O of the next sugar in the polymer, (c) Nucleic acids are polymers of nucleotides linked by bonds between the 3 -OH of the ribose ring of one nucleotide to the 5 -P04 of its neighboring nucleotide. All three of these polymerization processes involve bond formations accompanied by the elimination of water (dehydration synthesis reactions). 

Kricheldorf HR, Greber G (1971) N-silylated amino acid N-carboxylic acid anhydrides (oxazolidine-2.5-diones). Chem Ber 104 3131... 

Organo copper and lithium enolates of cyclic ketones, lactones, and lactams or acyclic ketones are converted with acylimidazoles or imidazole-N-carboxylates into the corresponding / -diketones or / -ketoesters ... 

Activation of a C-H bond requires a metallocarbenoid of suitable reactivity and electrophilicity.105-115 Most of the early literature on metal-catalyzed carbenoid reactions used copper complexes as the catalysts.46,116 Several chiral complexes with Ce-symmetric ligands have been explored for selective C-H insertion in the last decade.117-127 However, only a few isolated cases have been reported of impressive asymmetric induction in copper-catalyzed C-H insertion reactions.118,124 The scope of carbenoid-induced C-H insertion expanded greatly with the introduction of dirhodium complexes as catalysts. Building on initial findings from achiral catalysts, four types of chiral rhodium(n) complexes have been developed for enantioselective catalysis in C-H activation reactions. They are rhodium(n) carboxylates, rhodium(n) carboxamidates, rhodium(n) phosphates, and < // < -metallated arylphosphine rhodium(n) complexes. 

N-Carboxylic esters are readily cleaved under basic conditions. It is not known whether direct cleavage of the ester group is initiated by nucleophilic attack on the carbonyl group (c/. cleavage of acyl groups, Section 3.05.2.6) or whether the ester group is initially hydrolyzed. 

Wiesenberg, G. L. B., Schwarzbauer, I, Schmidt, M. W. I., and Schwark, L. (2004). Source and turnover of organic matter in agricultural soils derived from n-alkane/n-carboxylic acid compositions and C-isotope signatures. Org. Geochem. 35,1371-1393. 

Class D /3-lactamases show specificity toward oxacillins and are therefore named oxacillinases. In this class, the catalytic serine is activated by an N-carboxylated lysine <2001PNA14280, 2003PSC82>. 

Table 7-12 Flavor Character of Some N-Carboxylic Acids...

Enolate > amine > azo compounds > ring N > carboxylate > ether > carbonyl... 

Other base catalyzed methods for N-carboxylation of amines and hydrazines using CO2 and CS2 to generate the corresponding carbamate or thiocarbamate, respectively, are provided (1). Urea derivatives of Step 1 have also been prepared and are described (2). 

Ethoxyvinyllithium also adds stereoselectively to 1 to provide an adduct that is converted in several steps to the < n/(-carboxylic aeid 4. The, vvn-isomer 5 is available by addition of methyllithium, trapping with QH SeCI, and a sila-Pummerer rearrangement (Scheme 11). 

Phylogeny of Hydrocarbon Chains. An important chapter in the geochemistry of oil shales is the one dealing with the "genealogy" of the final products - the hydrocarbons. The results (28) of the phylogenetic study of the serie carboxylic acids aldehydes alcohols - hydrocarbons from the bitumen of a sample from the Irati F. showed no correlation between n-acids (C ) (C-.-.-C ) and n-tty drocarbons (C (the linear correlation coefficient 6 = 0,15). Between n-carboxylic acids (C ) and normal carbonyl/hydroxy com... 

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