Substituted hydrocarbons amino acids

Synthetic methods targeting amino acid incorporation into functional materials vary widely. Free-radical polymerization of various amino acid substituted acrylates has produced many hydrocarbon-amino acid materials [161, 162]. In separate efforts, MorceUet and Endo have synthesized and meticulously characterized a library of polymers using this chain addition chemistry [163- 166]. Grubbs has shown ROMP to be successful in this motif, polymerizing amino add substituted norbornenes [167-168]. To remain within the scope of this review, the next section wiU focus only on ADMET polymerization as a method of amino add and peptide incorporation into polyethylene-based polymers. 

The amino acid 26, which has been isolated from various Amanita fungi [35], is one of the few examples of a natural product with an achiral allene moiety (Scheme 18.10) and was prepared inter alia by Strecker synthesis and also substitution reactions of allenic bromides and phosphates [36]. Recently, even unfunctionalized allenes have been found in nature seven allenic hydrocarbons 27 with chain lengths ranging from C23 to C31 were isolated from the skin of the Australian scarab beetle Anti-trogus consanguineus and related species (Scheme 18.10) [37]. Also these allenes do not occur in enantiomerically pure form, but with enantiomeric excesses of86-89% ec. 

Certain fundamental characteristics of MECC that influence retention have been investigated (5). The technique has been used in the analysis of a variety of samples including phenolic compounds (1), phenylthiohydantoin—amino acids (6), and metabolites of vitamin Bg (7). In related electrokinetic separation techniques, substituted benzene compounds have been separated based on the formation of inclusion complexes with an ionic cyclodextrin derivative in the mobile phase (8) and polyaromatic hydrocarbons have been separated based on solvophobic interactions with a tetraakyl— ammonium ion in the mobile phase (9). The effects of injection procedures on efficiency have also been studied (10). 

When ammonia is substituted in organic acids in place of a hydrogen atom of the hydrocarbon radical we obtain amino acids. 

Derivatives of the amino acid type in which phenyl hydrazine, as an amjne, is substituted for a hydrogen atom of the hydrocarbon radical of an acid. They are known as hydrazino acidSy e.g. ... 

As both nitration and sulphonation take place with comparative ease, with either hydrocarbons or acids, and as the nitro compounds yield amino compounds and these yield diazo compounds, with their numerous reactions, in particular the Sandmeyer reaction for obtaining nitriles and as sulphonic acids are easily converted into phenols or nitriles it will be seen that by a combination of these synthetic reactions practically any desired ring-substituted mono-basic or poly-basic ring-carboxy acid may be obtained. 

Amino acid residues, except hydrocarbon chains, may provide nucleophilic sites (electron-rich centers) or electrophilic sites (electron-deficient centers) for chemical modifications. Electron-rich centers include sulfur nucleophiles (thiol of Cys and thioether of Thr), nitrogen nucleophiles (e-amino of Lys, imidazole of His and Guanidyl of Arg), oxygen nucleophiles (phenolic of Tyr, carboxyl of Asp and Glu and hydroxyl of Ser and Thr), and carbon nucleophile (a-position of indole ring of Trp), with an increasing nucleophilicity in that order. They provide nucleophilic sites for alkylation (nncleophilic substitution), acylation, addition and oxidation at pH near or above their pK values. Electron-deficient centers include ammonium cation of Lys, guanidiiun cation of Arg and imidazolium cation of His. They provide electrophilic sites for metalation and reduction at pH near or below their pK values. 

Mercapturic acid production seems to have first call on the sulphur amino acid reserves and serious deficiency states can be induced in rats by hepatotoxic hydrocarbons. Diets high in cysteine and methionine will protect against the liver damage. Some mercapturic acid production may also result from reaction of protein thiol groups with the hydrocarbons, hydrolysis of the protein to the S-substituted cysteine and its N-acylation. However, the vast majority is formed via the glutathione adducts if the hydrocarbon dose is not so great as to deplete the glutathione reserves of the liver. 

One of the most general and frequently applied indirect methods is the transformation of an organic compound into a nitrocompound. The method is applied to hydrocarbons and other aromatic compounds, mainly those bearing a phenyl ring, e.g. phenols, substituted anilines, phenyl-bearing amino acids etc. The nitrating mixture consists of nitric acid, either pure or... 

Since the main reaction product is /3-alanine, the propionic acid group evidently migrates more readily than the methyl group. It appears that in aliphatic and alicyclic /3-keto esters the acetic or substituted acetic ester residue migrates in preference to the hydrocarbon residue thus the reaction of substituted acetoacetic esters with hydrazoic acid affords a convenient way to synthesize a-amino acids in excellent yields. ... 

The synthesis of A/-acyl-a-chloroglycine and its use in the preparation of other a-substituted glycines has been described.N-Acylhemiaminals, prepared from glyoxylic acid and amides, carbamates, or ureas, can be converted into N-acyl-a-arylglycines by reaction with aromatic hydrocarbons in sulphuric acid. The same type of hemiaminals may be converted into N-acyl-y-keto-a-amino-acids by reactions with 1,3-dicarbonyl compounds again in the presence of concentrated sulphuric acid. °°... 

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