Carbonic acid amino derivatives

Amino-2-hydroxybenZOiC acid. This derivative (18) more commonly known as 4-aminosa1icy1ic acid, forms white crystals from ethanol, melts with effervescence and darkens on exposure to light and air. A reddish-brown crystalline powder is obtained on recrystallization from ethanol —diethyl ether. The compound is soluble ia dilute solutioas of nitric acid and sodium hydroxide, ethanol, and acetone slightly soluble in water and diethyl ether and virtually insoluble in benzene, chloroform or carbon tetrachloride. It is unstable in aqueous solution and decarboxylates to form 3-amiaophenol. Because of the instabihty of the free acid, it is usually prepared as the hydrochloride salt, mp 224 °C (dec), dissociation constant p 3.25. 

The preparative value of this compound lies in the surprising fact that bis(l,3-diphenylimidazolidinylidenc-2) behaves in many reactions ie.g., with aromatic aldehydes,2,7 and with carbon acids 2 7-fJ) as if it dissociated to form a nucleophilic carbene. The hydrolytic cleavage of these derived imidazolidine derivatives makes possible the preparation of formyl compounds, so that the amino olefin can be considered as a potential carbonyla-tion reagent. In many reactions it is not necessary to isolate... 

The most widely used method for the preparation of [l,2,4]triazolo[3,4-A][l,3,4]thiadiazoles 85 employs 4-amino-5-thio-4/7-[l,2,4]triazoles 83 or 4-amino[l,2,4]-triazole-5(47T)-thiones 84 as starting materials. The reaction of the triazoles 83 or 84 with carbonic acid derivatives furnishes [l,2,4]triazolo[3,4-4][l,3,4]thiadiazoles with a heteroatom substituent (N, O, S) at position 6 the O- and S-functions are formulated as 6-hydroxy and 6-thio derivatives 85a or as thiadiazol-(5/7)6-ones and -thiadiazole-(577)6-thiones 85b, respectively reaction with carboxylic acid derivatives provides the 6-substituted-[l,2,4]triazolo[3,4-4][l,3,4]-thiadiazoles 85c (Equation 20 Table 3). 

Numerous reports published in recent years have focused on carbon-centered radicals derived from compounds with selected substitution patterns such as alkanes [40,43,47], halogenated alkanes [43,48,49,51-57], alkenes [19], benzene derivatives [43,47], ethers [51,58], aldehydes [48], amines [10,59], amino acids [23,60-67] etc. Particularly significant advances have been made in the theoretical treatment of radicals occurring in polymer chemistry and biological chemistry. The stabilization of radicals in all of these compounds is due to the interaction of the molecular orbital carrying the unpaired electron with energetically and spatially adjacent molecular orbitals, and four typical scenarios appear to cover all known cases [20]. 

Biochemical reactions include several types of decarboxylation reactions as shown in Eqs. (1)-(5), because the final product of aerobic metabolism is carbon dioxide. Amino acids result in amines, pyruvic acid and other a-keto acids form the corresponding aldehydes and carboxylic acids, depending on the cooperating coenzymes. Malonyl-CoA and its derivatives are decarboxylated to acyl-CoA. -Keto carboxylic acids, and their precursors (for example, the corresponding hydroxy acids) also liberate carbon dioxide under mild reaction conditions. 

Glycine is in a class by itself. It is the only protein amino acid that is not chiral. It is neither hydrophilic nor hydrophobic. With the exception of proline, all other protein amino acids are derived from it by substituting various groups on the oi carbon atom. Glycine is an important inhibitory neurotransmitter in the central nervous system. 

All human tissues are capable of synthesizing the nonessential amino acids, amino acid remodelling and conversion of non-amino-acid carbon skeletons into amino acids and other derivatives that contain nitrogen. However, the liver is the major site of metabolism of nitrogenous compounds in the body. Dietary proteins are the primary source of essential amino acids (or nitrogen). Digestion of dietary proteins produces amino acids, which are absorbed through epithelial cells and enter the blood. Various cells take up these amino acids that enter the cellular pools. 

Dietary purines are not an important source of uric acid. Quantitatively important amounts of purine are formed from amino acids, formate, and carbon dioxide in the body. Those purine ribonucleotides not incorporated into nucleic acids and derived from nucleic acid degradation are converted to xanthine or hypoxanthine and oxidized to uric acid (Figure 36-7). Allopurinol inhibits this last step, resulting in a fall in the plasma urate level and a decrease in the size of the urate pool. The more soluble xanthine and hypoxanthine are increased. 

Diomides. These compds are the dibasic acid derivs of ammonia or amines, and contain two -CONH2 groups. Numerous combinations of diacids, diamines, and amino acids have been interacted. Copolymers contg various proportions of two or more diacids have been prepd (Ref 2). The diamide of carbonic acid is called urea, H2NCONH2. It is a product of animal metabolism and is prepd industrially by reaction of CO2 with excess NH3 at high temp, or by an older method involving the hydrolysis of cyanamide (Ref 5)... 

FIGURE 22-9 Overview of amino acid biosynthesis. The carbon skeleton precursors derive from three sources glycolysis (pink), the citric acid cycle (blue), and the pentose phosphate pathway (purple). 

Direct amination of quinoxalinones with hydroxylamine-O-sulfonic acid produces the 1-amino derivatives (135) in 70-80% yield, and subsequent oxidation with lead tetraacetate gives the 1,2,4-benzotriazines (138). Benzotriazine formation probably involves the formation of an intermediate nitrene (136), ring expansion to a benzo-triazepinone (137) and subsequent loss of carbon monoxide. The nitrene (136 R = Ph) was trapped as the sulfoximide 139 when the oxidation was carried out in the presence of dimethyl sulfoxide.147... 

Sulphur and Carbon —Carbon Subsnlphide, Carbon Monosulpliide—Carbon Disulphide and its Derivatives, Reduction Products of Carton Disulphide, Tliio-aoids and -salts Derived from Carbon Disulphide—Carbon Oxysulplnde —Halogen Derivatives of Sulphur and Carbon—Amino-derivatives of Tluo-carbonic Acid—Thioeyanogcn and its Derivatives, Tluoeyame Acid and the Thiocyanates. 

The six carbons of the benzene ring of the aromatic amino acids are derived from the four carbons of erythrose 4-phosphate and two of the three carbons of phosphoenolpyruvate (PEP). The initial step in the pathway (Fig. 25-1, step a) is the condensation of erythrose 4-P with PEP and is catalyzed by 3-deoxy-D-arafrmo-heptulosonate-7-phosphate (DAHP) synthase. Closely analogous to an aldol condensation, the mechanism provides a surprise.10 When PEP containing lsO in the oxygen bridge to the phospho group reacts, the lsO is retained in the eliminated phosphate biochemical intuition would suggest that it should stay in the... 

Importantly, TV-carbamoyl derivatives of primary amines obtained from photolabile benzoins exist in varying proportions as cyclic hydroxyoxazolidinone tautomers. Therefore, the preparation of TV-carbamoyl derivatives of benzoins is applicable only for secondary amines and TV-alkylated amino acids. 244 At basic pH unsymmetrical benzoins, such as 3,5-dimethoxybenzoin, their mixed carbonate and carbamate derivatives, tend to equilibrate to the isomeric forms. Nevertheless, in TFA and aqueous solutions at pH 8 the structural integrity is fully maintained. 244 Preparation of 3,5-dimethoxybenzoin-derived carbamates of secondary amines and amino acids can be mediated by either CDI/methyl triflate in ni-tromethane 246 or 4-nitrophenyl chloroformate/DMAP in dry THF. 244 ... 

Entry Carbonic Acid Derivative Parent Peptide or Amino Acid Coupling Conditions Product Yield (%) Ref... 

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