Amino Decarboxylation

Aromatic diazonium salts need no further transformations but can be directly cyanated with Cu " CN, as demonstrated in the preparation of 1 " C1105". Alternatively, the use of diphenylphosphoryl azide permits a one-step amino-decarboxylation, without isolation of the intermediately formed acyl azides". ... 

Another protecting group of amines is 1-isopropylallyloxycarbonyl, which can be deprotected by decarboxylation and a /3-elimination reaction of the (tt-l-isopropylallyl)palladium intermediate under neutral conditions, generating CO2 and 4-methyl-1,3-pentadiene. The method can be applied to the amino acid 674 and peptides without racemization[437]. 

The reactions that amino acids undergo in living systems include transamination and decarboxylation... 

Amino acid-derived hormones include the catecholamines, epinephrine and norepinephrine (qv), and the thyroid hormones, thyroxine and triiodothyronine (see Thyroid AND ANTITHYROID PREPARATIONS). Catecholamines are synthesized from the amino acid tyrosine by a series of enzymatic reactions that include hydroxylations, decarboxylations, and methylations. Thyroid hormones also are derived from tyrosine iodination of the tyrosine residues on a large protein backbone results in the production of active hormone. 

Biosynthesis. Two closely related genes encode the three mammalian tachykinins. The preprotachykinin A gene encodes both substance P and substance K, while the preprotachykinin B gene encodes neuromedin K (45—47). The active sequences are flanked by the usual double-basic amino acid residues, and the carboxy-terrninal amino acid is a glycine residue which is decarboxylated to an amide. As with most neuropeptide precursors, intermediates in peptide processing can be detected, but their biological activities are not clear (ca 1994). 

Decarboxylation. Decarboxylation of linear and aromatic carboxyUc acids and of amino acids is common and of practical interest. L-Lysine [56-87-1] (48) can be synthesized by stereospecific decarboxylation of meso- (but not DL-) aa -diaminopimehc acid [2577-62-0] (49). The reaction is catalyzed by Bacillus sphaericus and proceeds in quantitative yields (92). 

L-tryptophan by hydroxylation to 5-hydroxy-L-tryptophan by the enzyme, ttyptophan-5-hydroxylase. 5-Hydroxy-L-tryptophan is then rapidly decarboxylated by aromatic-L-amino acid deacarboxylase to 5-HT. The actions of 5-HT as a neurottansmitter ate terminated by neuronal reuptake and metabobsm. 

With active methylene compounds, the carbanion substitutes for the hydroxyl group of aHyl alcohol (17,20). Reaction of aHyl alcohol with acetylacetone at 85°C for 3 h yields 70% monoaHyl compound and 26% diaHyl compound. Malonic acid ester in which the hydrogen atom of its active methylene is substituted by A/-acetyl, undergoes the same substitution reaction with aHyl alcohol and subsequendy yields a-amino acid by decarboxylation (21). 

Hydroxylated amino acids (eg, 4-hydroxyproline, 5-hydroxylysine) and A/-methylated amino acids (eg, /V-methylhistidine) are obtained by the acid hydrolysis of proteins. y-Carboxyglutamic acid occurs as a component of some sections of protein molecules it decarboxylates spontaneously to L-glutamate at low pH. These examples are formed upon the nontranslational modification of protein and are often called secondary protein amino acids... 

Strecker Degradation (Oxidative Deamination), Mild oxidizing agents such as aqueous sodium hypochlorite or aqueous A-bromosuccinimide, cause decarboxylation and concurrent deamination of amino acids to give aldehydes. 

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. 

Other chemicals of possible concern for health and safety found ia yeast proteias iaclude tyramiae (0—2.25 mg/g) and histamine (0.2—2.8 mg/g), formed by decarboxylation of the corresponding amino acids (38). These compounds are also found ia other fermeated (including pickled) foods. Their preseace ia yeast extracts used as condiments coatributes very Htde to human iatake. Likewise, the nephrotoxic compouad lysiaoalaniae has beea ideatified ia alkah-treated yeast extracts, at a level of 0.12 mg/g. However, the chemical occurs at similar low coaceatratioas ia almost all heat- and alkaU-treated foods. 

Imidazole-4-carboxylic acid, 5-amino-cyclization, 5, 583 decarboxylation, 5, 434—435 ethyl ester diazotization, 5, 414 synthesis, 5, 477... 

Claisen ester condensation, 6, 279 Thiazolecarboxylic acid chlorides reactions, 6, 279-280 Thiazolecarboxylic acid hydrazides synthesis, 6, 280 Thiazolecarboxylic acids acidity, 6, 279 decarboxylation, 6, 279 reactions, S, 92 6, 274 Thiazole-2-carboxylic acids decarboxylation, S, 92 Thiazole-4-carboxylic acids stability, S, 92 Thiazole-5-carboxylic acids decarboxylation, S, 92 Thiazole-4,5-dicarboxylic acid, 2-amino-diethyl ester reduction, 6, 279 Thiazole-4,5-dicarboxylic acids diethyl ester saponification, 6, 279 Thiazolediones diazo coupling, 5, 59 Thiazoles, 6, 235-331 ab initio calculations, 6, 236 acidity, S, 49 acylation, 6, 256 alkylation, S, 58, 73 6, 253, 256 analytical uses, 6, 328 antifogging agents... 

Benzyioxycarbonyi chioride (Cbz-Ci, benzyi cbioroformate) [501-53-1] M 170.6, b 103 /20mm, d 1.195, n 1.5190. Commercial material is better than 95% pure and may contain some toluene, benzyl alcohol, benzyl chloride and HCl. After long storage (e.g. two years at 4 , Greenstein and Winitz [The Chemistry of the Amino Acids Voi 2 p. 890, J Wiley and Sons NY, 1961] recommended that the liquid should be flushed with a stream of dry air, filtered and stored over sodium sulfate to remove CO2 and HCl which are formed by decomposition. It may further be distilled from an oil bath at a temperature below 85 because Thiel and Dent [Annalen 301 257 1898] stated that benzyioxycarbonyi chloride decarboxylates to benzyl chloride slowly at 100 and vigorously at 155 . Redistillation at higher vac below 85 yields material which shows no other peaks than those of benzyioxycarbonyi chloride by NMR spectroscopy. LACHRYMATORY and TOXIC. 

Triazole has been prepared by the oxidation of substituted 1,2,4-triazoles, by the treatment of urazole with phosphorus pentasulfide, by heating equimolar quantities of formyl-hydrazine and formamide, by removal of the amino function of 4-amino-l,2,4-triazole, by oxidation of l,2,4-triazole-3(5)-thiol with hydrogen peroxide, by decarboxylation of 1,2,4-triazole-3(5)-carboxylic acid, by heating hydrazine salts with form-amide,by rapidly distilling hydrazine hydrate mixed with two molar equivalents of formamide, i by heating N,N -diformyl-hydrazine with excess ammonia in an autoclave at 200° for 24 hours, and by the reaction of 1,3,5-triazine and hydrazine monohydrochloride. ... 

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