Amino-acid Salts

Amino-acids can, of course, form basic and acidic salts, and the frequencies arising in hydrochlorides have already been discussed above. Salt formation through the carboxyl group removes the 

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Cram and his coworkers have pioneered the use of bis-binaphthyl crowns as chiral com-plexing agents for ammonium salts and amino acid salts. In these systems, the chiral binaphthyl unit provides a steric barrier within the macrocycle which allows discrimina-... 

Substances determined amines, amine salts, amino acids, salts of acids... 

Parenteral nutrition (amino acid salts) and arginine... 

Amino Acid Salts as Lewis Acids for Asymmetric Diels-Alder Reactions... 

Figure 5-7. Transition state of amino acid salt catalyzed Diels-Alder reaction. Reprinted with permission by Am. Chem. Soc., Ref. 34.

TABLE 5-3. Solvent Effect of Amino Acid Salt-Catalyzed Diels-Alder Reaction... 

The movement of solutes from the external environment into the cell is usually achieved using cell membrane-spanning proteins that facilitate solute transfer. These are necessary, since most solutes (e.g. sugars, amino acids, salts) will not readily diffuse through the hydrophobic cell membrane. Movement of solutes into the epithelial cell can involve a variety of protein carriers or channels including (see Figure 1) ... 

Most of the work on chiral recognition has been carried out with amino-acid ester salts. The limited number of available data of similar experiments with amino-acid salts point to an increased enantiomeric differentiation (Table 69 Peacock and Cram, 1976). The reason might be the higher -acidity of the carboxyl group (vide ir fra). In solid-liquid chromatography (see Table 68) the difference between amino-acid salts and amino-acid ester salts is not consistent and not always in favour of the amino-acid salts. However, it should be... 

With amino-acid salts the effect of the medium is considerably larger. Peacock and Cram (1976) reported that the degree of chiral recognition of DL-phenylglycine perchlorate by crown ether [285] depends on the ratio of acetonitrile and chloroform. The observed EDC values vary from 6 to 52, which corresponds to a difference in free energy of —1.15 kcal mol-1 (Table 72). The optimum is very sharply defined (23.1% of acetonitrile) and is... 

The role of these tastes has been nicely summarized Taste is in charge of evaluating the nutritious content of food and preventing the ingestion of toxic substances. Sweet taste permits the identification of energy-rich nutrients, umami allows the recognition of amino acids, salt taste ensures the proper dietary electrolyte balance, and sour and bitter warn against the intake of potentially noxious and/or poisonous chemicals. ... 

Different insect species posses different gustatory receptor cells, their response spectra being adapted to the perception of chemical components distributed in their host plant species (9 ). Taste perception in P. brassicae larvae forms a representative example for phytophagous insects, which are able to discriminate a number of compounds like sugars, amino acids, salts, and secondary plant substances acting as feeding inhibitors or feeding incitants (3,6,, 10). 

Nylon 6 is also a polyamide, but is made from the monomer e-caprolactam, which is a cyclic amide of e-aminocaproic acid. Heat opens the lactam ring to give the amino acid salt, which forms amide bonds with other molecules by eliminating water. 

It has recently been found that the bis-spirophosphorane (182) (easily available from catechol and phosphorus trichloride) undergoes addition of a peptide carboxylate giving the reactive intermediate (183) which can be further reacted with O- protected amino acid salts to produce a new peptide (for example the tripeptide 184) with very little (0.1%) racemization (Scheme 29) (82CC298). 

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. 

A simple amino acid salt, sodium L-phenylglycinate, catalyses the enantioselective... 

Our interest in expanding the acylative pyrrole annulation approach to additional heterocyclic systems has led to an efficient synthesis of pyrrolo[3,2-c]pyridin-2-ones and pyrido[3,4-6]pyrrolizidin-l-ones starting from 4-chloro-N-benzyl-2(l//)-pyridinone and amino acid salts.811 Over the years pyrrolo[3,2-c]pyridines (5-azaindoles)41 have been of interest for applications as elements in new drug design, nucleotide analogues,42 and biochemical tools. However, available synthetic routes to multifunctionalized members from this class of heterocyclic structures are limited.41 43... 

To test the generality of this reaction, the indole systems 70a,b were prepared from hexahydro-8-oxopyrrolo[ 1,2-a]indole 67 and tetrahydro-4-oxindole 68 (Scheme 11). These compounds in turn were readily obtained from cyclohexane-1,3-one and the appropriate amino acid salt according to Franck s pyrrole acylation protocol.53 Attempts to directly oxidize 67 or 68 to the hydroxyindole oxidation state using DDQ met with failure despite numerous attempts involving variation in solvent and reaction temperature. To circumvent this limitation, it was reasoned that... 

The iV-Boc-imine-derived Mannich products can readily be converted into the corresponding a,P-branched-P-amino acids (f)2,3-amino acids). For example, oxidation of the product 1 to the carboxylic acid followed by acid-mediated deprotection provided the amino acid salt 2 without... 

Fig. 12. A posdble binding of an amino acid salt to Cyclo-(Pio ly)4. An inward rotation of tiie four Pro carbonyl groups can give the second binding site on the opponte side of the peptide plane...

FI. Kimoto, K. Saigo, Y. Ohashi, M. Flasegawa, Molecular recognition in the formation of conglomerate crystal. 2. The role of arenesulfonic acid in the conglomerate crystals of amino acid salts. Bull. Chem. Soc. Jap. 62 (1989) 2189-2195. 

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