Amino acids as building blocks

Synthesis of N-Alkyl Amino Acids as Building Blocks for N-... 

Aliphatic aldehydes typically provide only moderate yields in the Biginelli reaction unless special reaction conditions are employed, such as Lewis-acid catalysts or solvent-free methods, or the aldehydes are used in protected form [96]. The C4-unsubstituted DHPM can be prepared in a similar manner employing suitable formaldehyde synthons [96]. Of particular interest are reactions where the aldehyde component is derived from a carbohydrate. In such transformations, DHPMs having a sugar-like moiety in position 4 (C-nucleoside analogues) are obtained (see Section 4.7) [97-106]. Also of interest is the use of masked amino acids as building blocks [107, 108]. In a few cases, bisaldehydes have been used as synthons in Biginelli reactions [89, 109, 110]. 

Fig. 21 Enzymatic synthesis of unnatural amino acids as building blocks for omapatrilat. (a-c) Enzymatic approaches to 6-oxonorleucine analogs...

Arsequell, G. and Valencia, G. (1997) 0-Glycosyl a-amino acids as building blocks for glycopeptide synthesis. Tetrahedron Asymmetry 8, 2839-2876. 

Using photolabile amino acids as building blocks, small photolabile peptides can be made by total synthesis, rather than by chemical modification. This method is preferable as analogs with structures closely similar to the unmodified ligand can be made. However, total synthesis will not become a method of choice in most laboratories until reagents fully compatible with rapid solid-phase peptide chemistry have been fully explored. 

The importance of amino acids as building blocks for asymmetric synthesis is well documented (105). A number of amino acids have been shown to exist as conglomerates. Shi-... 

Proteins are polymers of amino acids. With 20 different fundamental amino acids as building blocks, an extraordinarily large variety of proteins can be biosynthesized under the direction of the genetic code. 

The overall charge of a protein is dependent on the number of acidic and basic amino acids that are charged at a particular pH. Proteins are least soluble in aqueous solution at pH equal to its p7. With a large number of diversified a-amino acids as building blocks, nature is able to promote an extremely large variety of combinations, and can thus control the subtle functions performed by proteins. 

Production of an enzyme by a bacterial or a fungal strain is more complicated since a protein is composed of 20 amino acids as building blocks. Theoretical protein mass yield on glucose is then best estimated from the stoichiometry of the building blocks and is close to 50%, according to Equation 6.1, based on the elemental composition (Nielsen et al., 2002) ... 

Proteins are macromolecules made from amino acids as building blocks and are arranged in a three-dimensional folded strucmre. The basic structure of amino acids is given Fig. 1.15. As one of the most important classes of biomolecules and a major component of the natural tissues, proteins and other amino acid-derived polymers have been a preferred biomaterial for sutures, haemostatic agents, scaffolds for tissue engineering, and dmg dehvery vehicles. Furthermore, protein based biomaterials are known to undergo naturally controlled degradation processes (Meinel et al., 2005). 

The asymmetric synthesis via a-transaminases was described for L-phenylalanine and L-homophenylalanine in several reports and reviews [17,62,86]. Herein the focus is on ffl-transaminases that catalyzed the asymmetric synthesis of optically pure nonproteinogenic amino acids as building blocks for peptidomimetic and other pharmaceutical compounds. The overall advantage of -transaminase-catalyzed reactions is the ability to use achiral amino donors like benzylamine, which thermodynamically favors the equilibriinn toward the product side. 

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