A diamino acids

With the exception of cystine, a, a -diamino acids represent a class of compounds not found naturally in biological samples. However, it should be noted that such compounds have been isolated previously from certain... 

Scheme 1 Selective N -Protection of a Diamino Acid with a Weak Acylating Agentf ...

An alternative, new approach for the synthesis of co-carboxamide-containing amino acid derivatives is based on the oxidation of suitably protected a,a-diamino acids (2,4-diamino-butyric acid, ornithine, lysine) with permanganatet or ruthenium(lV) oxide,as shown in Scheme 6. The co-Boc-carboxamide group is stable toward catalytic hydrogenation, acetic acid, and 10% TEA/CH2CI2, is unstable in the presence of 1M NaOH/MeOH, and is cleaved with methanolic hydrazine hydrate, 25% TFA/CH2CI2, 25% HBr/AcOH, or HF.P l... 

Berg et al. synthesized peptide oligomers that incorporated 4-cyanoazobenzene for erasable holographic data storage [168]. The oligomer is a diamino acid-N -substituted peptide (DNO) repeat unit, compound 4, with an azobenzene side chain... 

Activation of amide bonds with an acid (usually at elevated temperatures) to facilitate the 1,2- (or 2,3-) bond formation is a useful method to prepare imidazoles and benzimidazoles (see Section 4.02.9.2(i)). For example, )3-ketoester 1093 possessing a diamino acid (diaminobutanoic acid or ornithine) group is activated by AcOH to form bicyclic imidazole 1094 <2003SL780>. A library of imidazolines, exemplified in Scheme 265, was prepared from Ugi products under acidic conditions <1999TL7925>. 

Although (V-sulfonylimines are useful precursors for the preparation of important synthetic intermediates such as oxaziridines and aziridines, as well as for the synthesis of compounds of biological importance such as e/yfAro-a, -diamino acids, only a handful of reports have been published on the use of )V (Diphenyl-methylene)-4-methylbenzenesulfonamide (2) no reports have appeared for )V-(Diphenylmethylene)benzenesulfonamide (1). 

The wool protein chains are joined periodically through the disulfide crosslinked cystine, a diamino acid that is contained within two adjacent chains. About 40% of the protein chains spiral upon themselves and internally hydrogen bond to form an a-helix. Near the periodic cystine... 

V. Synthesis of ot-Hydroxy- and a-Mercapto-a-amino Acids, a,a-Diamino Acids and the Corresponding Peptides and Piperazinediones.282... 

Matsumura, K., H. Shimadzu, O. Miyashita, and N. Hashimito Studies of Nitriles. Part 9. Reactions of 2-Acylamino-3,3-dichloroacrylic Amide and -N-Acyl-amide with Aliphatic Amines. (2). Syntheses of Some a,a-Diamino-Acid Derivatives. Chem. Pharm. Bull. 24, 941 (1976). 

Yamabe, Seno, and Takai [39] investigated the permeability of a monocarboxylic amino acid glutamic) and a diamino acid (lysine), solutions of which mixed with sodium chloride (0.1 N) were placed in the central cell of a five-compartment electrodialyzer. In the adjacent cells, which were separated from the central compartment by a cation-exchange membrane (on the cathodic side) and an anion-exchange membrane (on the anodic side), was placed 0.1 N sodium chloride solution. The changes in concentration of chloride and amino acid were determined as a function of the pH value in the central cell, which was varied by addition of alkali or hydrochloric acid. 

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