Amides Aspartic acid

C. Monoaminodicarboxylic acids and their amides Aspartic acid Asparagine Glutamic acid Glutamine... 

Acidic amino acids and their m-amides Aspartic acid Glutamic acid Asparagine Glutamine -CH2-COOH -(CH2)2-C00H -CH2-CONH2 -(CH2)2-C0NH2... 

Alitame (trade name Adame) is a water-soluble, crystalline powder of high sweetness potency (2000X, 10% sucrose solution sweetness equivalence). The sweet taste is clean, and the time—intensity profile is similar to that of aspartame. Because it is a stericaHy hindered amide rather than an ester, ahtame is expected to be more stable than aspartame. At pH 2 to 4, the half-life of aUtame in solution is reported to be twice that of aspartame. The main decomposition pathways (Fig. 6) include conversion to the unsweet P-aspartic isomer (17) and hydrolysis to aspartic acid and alanine amide (96). No cyclization to diketopiperazine or hydrolysis of the alanine amide bond has been reported. AUtame-sweetened beverages, particularly colas, that have a pH below 4.0 can develop an off-flavor which can be avoided or minimized by the addition of edetic acid (EDTA) [60-00-4] (97). 

The carboxamidomethyl ester was prepared for use in peptide synthesis. It is formed from the cesium salt of an A-protected amino acid and o -chloroacet-amide (60-85% yield). It is cleaved with 0.5 M NaOH or NaHC03 in DMF/H2O. It is stable to the conditions required to remove BOC, Cbz, Fmoc, and t-butyl esters. It cannot be selectively cleaved in the presence of a benzyl ester of aspartic acid. ... 

A more general method for preparation ofa-amino acids is the amidotnalmatesynthesis, a straightforward extension of the malonic ester synthesis (Section 22.7). The reaction begins with conversion of diethyl acetamidomalonate into an eno-late ion by treatment with base, followed by S 2 alkylation with a primary alkyl halide. Hydrolysis of both the amide protecting group and the esters occurs when the alkylated product is warmed with aqueous acid, and decarboxylation then takes place to vield an a-amino acid. For example aspartic acid can be prepared from, ethyl bromoacetate, BrCh CCHEt ... 

In an attempt to design the p-turn-peptide-mimics, aspartic acid (an amino acid also known as aspartate) and lysine (an amino acid especially found in gelatin and casein) were attached to each amine group of 1,3-diaminoada-mantane in the form of amide bonds. The term p-turn refers to a peptide chain that forms a tight loop such that the carbonyl oxygen of one residue is hydrogen... 

The NPN content has been demonstrated to range from 15 to 37% at harvest (6, 7). The only published report of the composition showed the NPN fraction to be nutritionally unbalanced, containing mostly amino acids and amides (6). The major components were asparagine, 61% aspartic acid, 11% glutamic acid, 4% serine,... 

Fig. 6.27. Simplified representation of the reaction mechanisms by which aspartic acid residues can facilitate the hydrolytic cleavage of Asp-Xaa or Xaa-Asp peptide bonds. Pathway a begins as a nucleophilic attack of the C-flanking N-atom (i.e., the amide N-atom of the n+1 residue) at the carbonyl C-atom of the Asp side chain. Pathway b, which cleaves the Asp-Xaa bond, begins as a nucleophilic attack internal to the Asp residue. Pathway c, which cleaves the Xaa-Asp bond, is analogous to Pathway b, except that the attack is at the carbonyl C-atom of the N-flanking residue (i.e., the carbonyl of the n-1 residue).

Asparagine is derived from aspartic acid. Its side chain is an amide. 

Asparagine, the amide of aspartic acid, was first isolated by Robi-quet and Vauquelin, in 1806, from the juice of Asparagus officinalis hence its name. Not only is asparagine found in asparagus, but also in the seedlings of lupines, peas, vetches, etc., from which it is best and most easily prepared. 

Its composition, C H7N04, was established in 1833 by Boutron-Charlard and Pelouze, and confirmed by Liebig. In 1848 Piria showed that aspartic acid was converted into malic acid by the action of nitrous acid, and he regarded aspartic acid and asparagine as the two amides of malic acid... 

This idea of their constitution was proved to be erroneous by Kolbe in 1862, who showed that aspartic acid did not give off ammonia when boiled with dilute caustic alkali, and that asparagine only lost half of its nitrogen when thus treated. Aspartic acid was therefore not the amide of malic acid, but amino-succinic acid, and asparagine the amide of this compound. 

The major metal-binding amino acid side chains in proteins (Gurd and Wilcox, 1956 see Voet and Voet, 1990) (Table II) are carboxyl (aspartic acid and glutamic acid), imidazole (histidine), indole (tryptophan), thiol (cysteine), thioether (methionine), hydroxyl (serine, threonine, and tyrosine), and possibly amide groups (asparagine and glutamine, although... 

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