Aminoacids amino group

Preparation of optically active P-aminoesters, P-aminonitriles, and P-aminocarbox-amides are of special relevance for the synthesis of enantiomerically pure P-aminoacids compounds of special relevance in several areas of medicinal chemistry. The resolution of P-aminoesters can be carried out by acylation of the amino groups or by other biocatalytic reactions of the ester groups, such as hydrolysis, transesterification, or aminolysis. The resolution of ethyl ( )-3-aminobutyrate... 

Silk fibroin contains no cystine and the content of lysine and histidine is also low (about 1% in total), but it does contain tyrosine phenolic (13%) and serine alcoholic (16%) sidechains. Since glycine accounts for 44% of the total aminoacid content, an N-terminal glycine residue is reasonably representative of most of the primary amino dyeing sites in silk fibres. Amino acid analysis of hydrolysed reactive-dyed silk indicates that the reaction between fibroin and reactive dyes takes place mainly at the e-amino group of lysine, the imino group of histidine and the N-terminal amino group of the peptide chain. In an alkaline medium, the hydroxy groups of tyrosine and serine also react [114]. 

Much research has been carried out into the functionalisation of the primary amino groups on the surface of PAMAM dendrimers with a number of conjugates (e.g. aminoacids, sugars, lipids), leading to a variety of decorated PAMAM dendrimers with improved transfection abilities both in vitro and in vivo [192-201]. 

Only little is known about the structure of six-membered chelate rings in complexes with )3-aminoacids. The most probable is a distorted boat conformation with the more voluminous substituent neighboring the amino group in an equatorial arrangement. 

The same sequence of reactions was accomplished on the bicyclic iodide 16-R (Scheme 10), the reaction of which with tetrabutylammonium azide in toluene at 60 °C afforded the azide 33-R in 76% yield. Selective deprotection of the primary hydroxyl group of compound 33-R and Jones oxidation, finally afforded compound 35-R as masked glyco-aminoacid. The azido group was maintained in these compounds as protected equivalent of the amino group. 

A somewhat similar diazotization in the presence of HF Py was used for making fluoropenicillin (equation 18)34 and a-fluoroacids from various aminoacids (equation 19)35. When a secondary carbon vicinal to the amino group is present, a mixture of a-and f1-fluoroacids was obtained. Their ratio was controlled by the relative stability of the resulting carbocations and the HF concentration in the (HF)/Py complex36. 

C-terminal and N-terminal are the end and the start respectively, of a peptide chain in a protein. The N-terminal aminoacid in a protein has a fijee amino group. This group is often acylated. When it is free and protonated and positively charged at neutral pH, it may be also called NH2-terminal or NH3+ -terminal. At the C terminus, the carbo-xylgroup is free. Since it is mostly unprotonated and uncharged, the C-terminus may also be named carboxyterminal. 

The biogenesis of Winterstein s acid and phenylisoserine has been investigated in detail [42-43], These P-aminoacids are derived from phenylalanine, probably through a diotopic reaction involving the migration of the amino group from the a- to the P-carbon of the amino acid [44], Cinnamic acid was not incorporated in the yew P-amino acids [44],... 

Another example of selectivity is that aminoalcohols can be oxidised to aminoacids in slightly alkaline solution. In this application, gold is remarkably superior to other metals because the free amino group has a strong interaction with other catalytic metals such as Pd and Pt [361,363]. 

This review article is concerned with chemical behavior of organo-lithium, -aluminum and -zinc compounds in initiation reactions of diolefins, polar vinyls and oxirane compounds. Discussions are given with respect to the following five topics 1) lithium alkylamide as initiator for polymerizations of isoprene and 1,4-divinylbenzene 2) initiation of N-carboxy-a-aminoacid anhydride(NCA) by a primary amino group 3) activated aluminum alkyl and zinc alkyl 4) initiation of stereospecific polymerization of methyloxirane and 5) comparison of stereospecific polymerization of methyloxirane with Ziegler-Natta polymerization. A comprehensive interpretation is proposed for chemistry of reactivity and/or stereospecificity of organometallic compounds in ionic polymerizations. 

Initiation of N-Carboxy-g-Aminoacid Anhydride(NCA) by a Primary Amino Group... 

In the amicoumacins, AI-77 compounds, and xenocoumacins, where there is no oxygen function at C6, H6 resonates at ca. 6 7.5 as a triplet J 7-8 Hz, and H5, H7 as doublets, J 7-8Hz at ca. 5 6.8. In the spectra of these compounds the aminoisopentyldihydroisocoumarin system and the aminoacid moiety attached through amide formation with the 5 -amino group give rise to two distinct coupling systems whose connectivities can be established completely in favourable cases. 

A related example was provided by Jung and coworkers, ho reacted the insoluble polymeric active ester 27 (Scheme 1.6.13) with the free amino group of a soluble aminoacid- or peptide polyethyleneglycol ester 28. 

It seems appropriate to remember that there are also other classes of molecules that are catalytically active thanks to one of the mentioned mechanisms (ureas, thioureas, phosphoric acids, etc.) as well as molecules with two or more different functional sites (bifunctional organocatalysts) one of which is often an alcoholic/phenolic/carbojqrlic group (amino-alcohols, aminoacids, proline derivatives, aminophenols, etc.) they will be not discussed in this chapter because they have already been examined in previous chapters or because they contain nonsustainable elements. 

One of the known mechanisms of biosynthesis is shown in the next scheme. The enzyme aminotransferase transfers the amino group from the precursor amino acid to the a-ketoacid, which is rearranged into the product amino acid. In this process, the precursor amino acid is transformed into the corresponding a-ketoacid. It must be pointed out that besides transferring the amino group, the enzyme aminotransferase also preserves the stereochemistry the L-precursor amino acid leads to the formation of the L-product aminoacid. This mechanism presented below is for the biosynthesis of L-glutamic acid. 

As suggested by the name, the process of transamination effectively removes the amino group of one aminoacid and replaces it with a carbonyl group while affecting the opposite change on its reacting partner, that is. 

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