Amino acids as starting materials

Traditionally, amino acids have been utilized in the mainstream of organic chemistry primarily as building blocks for peptide syntheses. One may expect that in the future the use of amino acids as starting materials for non-peptide compounds will be a subject of ever-increasing interest. Many chiral target molecules with widely variable structures will be prepared from amino acids in the future. 

A simpler reaction using allylated amino acids as starting material may serve as an example (Scheme 84) [337] ... 

Figure 10 a-Amino acids as starting materials. Synthesis of (S)-8-hydroxyhexadecanoic acid, (5)-4-dodecanolide, fruiting-inducing cerebroside of Schizophyllum commune (Sch II), (5S,4S)-4-methyl-3-heptanol, and (—)-invictolide. 

Okuma et al. (2013) described a simple, rapid and efficient green synthesis of aryl methoxylated benzamides and 2-oxazolines from renewable Eucalyptus biomass-tar derivatives. One pot synthesis was realized using microwave irradiation as an alternative energy source, through a direct condensation reaction of amino alcohol with carboxylic acids as starting materials. 

Formation of N-Carboxy-(X-Amino AeidAnhydride (NCA) (85), NCAs are important as starting materials for amino acid polymers. They are prepared by the reaction of amino acids with phosgene in an aptotic solvent. 

Carboxylic acid, 161, also serves as starting material for a substituted pyrazine that has proven to be an important diuretic agent. As the first step in the synthesis the acid is converted to the corresponding amide (165). Treatment with a single equivalent of hypobromous acid effects Hoffmann rearrangement of only one of the amide groups. Ethanolysis of the intermediate carbamate leads directly to the amino ester (166). Exposure of the... 

Besides high effectiveness in the diastereoselective control of nucleophilic addition reactions, another major goal in the design of chiral auxiliaries is the use of readily available, chiral starting materials. The hexahydro-l//-pyrrolo[l,2-c]imidazole derivatives 9a-e are examples which use the inexpensive amino acid L-proline (7) as starting material. 

The use of backbone-modified poly (amino acids) as biomaterials was first suggested by Kohn and Langer (17) who prepared a polyester from N-protected trans-4-hydroxy-L-proline, and a poly(itiuno-carbonate) from tyrosine dipeptide as monomeric starting material (12,18). 

FIGURE 1 Schematic representation of the use of trifunctional amino acids as monomeric starting materials for the synthesis of pseudopoly-(amino acids), (a) Polymerization via the C terminus and the side chain R. (b) Polymerization via the N terminus and the side chain R. (c) Polymerization via the C terminus and the N terminus. The wavy line symbolizes any suitable nonamide bond. See text for details. ... 

Substances such as carbohydrates and amino acids as well as other small molecules available from natural sources are valuable starting materials in enantiospecific syntheses. Suggest reagents that could effect the following transformations, taking particular care to ensure that the product will be enantiomer-ically pure. 

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