Peptides amino acid chelates

Fig. 15 The newly introduced principle of single amino acid chelators (42, SAAC) which can directly be subjected to automated solid phase peptide syntheses...

Table 12. Superoxide dismutase activity of different Cui+-amino acid chelates. All the amino acids and peptides used were in the L-form. The cytochrome-c reductase assay was performed as given in Table 11 (179)...

Co(III)-chelated amino acid ester reactant and/or peptide product (Scheme 1). This basic difficulty was quickly pointed out (5), and has subsequently been examined and commented upon by others (6, 7). Such criticisms are well-founded since epimerization (or racemization) is a common problem, at least to some degree, in all chemical methods of synthesis where acyl-activation is employed. As a result, metal-activation methods have received little attention. However, since 1981 we have refined the Co(III) method such that very fast, clean, couplings can now be carried out using A-[Co(en)2((S)-AAOMe)]3+ reagents, which involve minimal (<2%) epimerization/racemization provided experimental conditions are strictly adhered to. 

Amino acids coordinated to (en)2Co(III) centers are the most useful in peptide synthesis, and general routes to the preparation of these important A/) O-chelates are described below. Many of the corresponding trien complexes are also available, usually as /32 isomers, but [Co(NH3)4(AAO)]2+ species are less accessible. The [Co(en)2(AAO)]2+ complexes have been reported for 19 of the 20 naturally occurring... 

It has been shown that the Claisen rearrangement of lithium enolates of amino acid enynol esters allows the synthesis of very sensitive y, 5-unsaturated amino acids with conjugated enyne side chains.The chelate-enolate Claisen rearrangement has also been applied to the synthesis of unsaturated polyhydroxylated amino acids, polyhydroxylated piperidines, and unsaturated peptides. ... 

Fig. 10. The peptide carbonyl and the free a-amino group of an amino acid may complex a metal ion to form a five-membered chelate.

Ac-Phc-Lys-OH, enzymatic synthesis, 156f Acesulfame K, stnicture, 7f Acetoin, in reactions of aldehydes with ammonium sulfide, 36-54 Acid chelators, 57-58 Acid synergism, description, 58 Acidic amino acid peptides, taste,... 

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