Amino acids and their derivatives

In Cosmetics. Amino acids and their derivatives occur in skin protein, and they exhibit a controlling or buffering effect of pH variation in skin and a bactericidal effect (216). Serine is one component of skin care cream or lotion. Ai-Acylglutamic acid triethanolamine monosalt is used for shampoo. Glucose glutamate is a moisturizing compound for hair and skin (234). 

Certain amino acids and their derivatives, although not found in proteins, nonetheless are biochemically important. A few of the more notable examples are shown in Figure 4.5. y-Aminobutyric acid, or GABA, is produced by the decarboxylation of glutamic acid and is a potent neurotransmitter. Histamine, which is synthesized by decarboxylation of histidine, and serotonin, which is derived from tryptophan, similarly function as neurotransmitters and regulators. /3-Alanine is found in nature in the peptides carnosine and anserine and is a component of pantothenic acid (a vitamin), which is a part of coenzyme A. Epinephrine (also known as adrenaline), derived from tyrosine, is an important hormone. Penicillamine is a constituent of the penicillin antibiotics. Ornithine, betaine, homocysteine, and homoserine are important metabolic intermediates. Citrulline is the immediate precursor of arginine. 

The most widely studied interactions between biologically active ligands and organotin(lV) cations relate to the amino acids and their derivatives (N- or S-protected amino acids and peptides), though new data on several of the most commonly occurring amino acids are still being published. This is specially true for aqueous speciation studies. Nice and very detailed reviews were published in this area by Molloy and Nath. ... 

Engel, M. H. and P. E. Hare (1985), Gas liquid chromatography of amino acids and their derivatives, in Barrett, G. C. (ed.), Chemistry and Biochemistry of the Amino Acids, Chapman Hall, London, pp. 462-499. 

WALLSGROVE, R.M., BENNETT, R.N., The biosynthesis of glucosinolates in Brassicas. In Amino Acids and Their Derivatives in Higher Plants, (R.M. Wallsgrove, ed.), Cambridge University Press, Cambridge. 1995, pp. 243-259. 

In terms of their chemical structures, signalling molecules fall into five main categories (i) peptides, (ii) steroids, (iii) amino acids and their derivatives, (iv) fatty acid derivatives, and (v) nucleotides. 

Cavazzini, A. et al.. Study of mechanisms of chiral discrimination of amino acids and their derivatives on a teicoplanin-based chiral stationary phase, J. Chromatogr. A, 1031, 143, 2004. 

A potential versatile route into a-amino acids and their derivatives is via a combination of (i) nitrile hydratase/amidase-mediated conversion of substituted malo-nonitriles to the corresponding amide/acid followed by (ii) stereospecific Hofmann rearrangement of the amide group to the corresponding amine. Using a series of a,a-disubstituted malononitriles 14, cyanocarboxamides 15 and bis-carboxamides 16, the substrate specificity of the nitrile hydratase and amidase from Rhodococcus rhodochrous IF015564 was initially examined (Scheme 2.7). The amidase hydrolyzed the diamide 16 to produce (R)-17 with 95% conversion and 98%e.e. Amide 17 was then chemically converted to a precursor of (S)-a-methyldopa. It was found... 

The utilization of a-amino acids and their derived 6-araino alcohols in asymmetric synthesis has been extensive. A number of procedures have been reported for the reduction of a variety of amino acid derivatives however, the direct reduction of a-am1no acids with borane has proven to be exceptionally convenient for laboratory-scale reactions. These reductions characteristically proceed in high yield with no perceptible racemization. The resulting p-amino alcohols can, in turn, be transformed into oxazolidinones, which have proven to be versatile chiral auxiliaries. Besides the highly diastereoselective aldol addition reactions, enolates of N-acyl oxazolidinones have been used in conjunction with asymmetric alkylations, halogenations, hydroxylations, acylations, and azide transfer processes, all of which proceed with excellent levels of stereoselectivity. 

However, the CMPA concept for CLEC. introduced by Lindner and co-workers139 for the resolution of dansyl amino acids using a chiral triamine and Zn(II) as transient metal ions parallel to the work of Gil-Av146, allowed the further development and successful use of amino acids and their derivatives together with Cu(II) as CMPAs in reverse-phase systems for the direct resolution of, for example, a-amino acids146. 

C) Intramolecular acylation of amino acids and their derivatives. 

Stereoselective elongation of the carbon skeleton is the central point of the synthesis of amino sugars from a-amino acids and their derivatives (Scheme 1). 

Reductive Alkylation of Amino Acids and Their Derivatives... 

Ligating Ambivalency vol. 9, Amino Acids and their Derivatives as Ambivalent Ligands , Dekker, New York. 

Studies of Frankel and Katchalski (31) proved that carbon dioxide reacts reversibly with amino acids and their derivatives giving the respective carbamic acids, viz. 

Amphoteric surfactants contain both an acidic and basic hydrophilic group. Ether or hydroxyl groups may also be present to enhance the hydrophilicity of the surfactant molecule. Examples of amphoteric surfactants include amino acids and their derivatives in which the nitrogen atom tends to become protonated with decreasing pH of the solution. Amino acid salts, under these conditions, contain both a positive and a negative charge on the same molecule. 

Amino acids and their derivatives undergo a wide range of reactions, e.g. racemization, peptide bond formation, ester hydrolysis, aldol-type condensation, Schiff base formation and redox reactions, which are catalyzed by coordination to a metal centre. A number of reviews are available which cover some of these reactions.48,69,70... 

The third section will contain direct reactions of stable chelates. This is a large and diffuse topic and many examples of reactions of this type are included in Chapter 7.4. In the current chapter, a more detailed discussion of the most important areas, namely complexes of fl-diketones and q-amino acids and their derivatives, will be offered. Also some important organic reactions of carbonyl compounds will be considered with regard to the nature of their chelated transition states and the effects these have on product formation. 

Armstrong et al. [54] resolved the enantiomers of some amino acids and their derivatives on x-CD-based CSPs using 1% aqueous triethylammonium acetate (pH 5.1). The same authors also tested a /LCD CSP for the chiral resolution of amino acids [55]. In addition, they evaluated a y-CD phase for the enantiomeric resolution of some dansyl amino acids and other drugs. The mobile phase was 38% methanol with 1% triethylammonium acetate [58]. In another study, the same authors reported the chiral resolution of 25 pairs of amino acids in less than 30 min [63]. The enantiomers of some /i-adrcncrgic blockers were resolved on a /LCD stationary phase, with 1% aqueous triethylammonium acetate, containing methanol, as the mobile phase [9,48]. 

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