N-acetylamino acids

These observations are common to the series of N-acetylamino acids which have been investigated. Whereas the carbon monoxide to carbon dioxide yield for the aliphatic carboxylic acids are in the approximate ratio of 1 10, the corresponding ratio for the N-acetyl amino acids is much smaller, because of the much smaller yields for carbon monoxide. This suggests that there must be another site on which the ejected electron can be trapped with greater efficiency than that for trapping on the carboxyl group. 

Tlie amino group of the racemic amino acid is acetylated with acetic anhydride to give racemic N-acetylamino acid. The deacylase hydrolyzes only the i. enantiomer, which is thereby separated from the d enantiomer. The latter is then chemically hydrolyzed to give the free d amino acid. 

Lack of congruence of sequence and structure with function Common sequence and structure, indeed identity of the protein itself, do not imply a unique function Each pair, o-succinylbenzoate synthase (OSBS)-N-acetylamino acid racemase, and lens crystallin-lactate dehydrogenase, share sequence and structure but differ in function. 

Enolases mandelate racemase (MR), muconate-lactonizing enzyme (MLE), N-acetylamino acid racemase (NAAR) Hasson, 1998 Palmer, 1999... 

NAAR N-acetylamino acid racemase OSBS O-succinylbenzoate synthase. 

N -Acetylamino acid hydrolase N -Acetyl amino acids Amino acids 36, 37... 

H-labeled model compounds prepared from the inactivator and N-acetylamino acids showed that only histidine and cysteine were labeled in the protein. 

Mercuric salts of carboxylic acids decompose in uv light or in the presence of peroxides to form alkylmercury derivatives. Aqueous peroxydisulfate can be used to decarboxylate N-acetylamino acids to give aldehydes or ketones, acetamide, and CO2. ... 

The most established method for enzymatic L-amino acid synthesis is the resolution of racemates of N-acetylamino acids by acylase I from AspergiUus oryzae fungus. The N-acetyl-L-amino acid is cleaved to yield L-amino acid whereas the N-acetyl-D-amino acid does not react. After separation of the L-amino acid through ion exchange chromatography or crystallization, the remaining N-acetyl-D-amino acid can be... 

Esterification with diazomethane. Treatment with acetic anhydride Methyl esters of N-acetylamino acids 18,19... 

Table I. y-ray Induced Degradation of Solid N-acetylamino Acids, GH3CONHCH(R)COOH ...

Table III. Ammonia and Fatty Acid Yields in the y-Radiolysis of Aliphatic N-Acetylamino Acid...

The model chiral phases, iV-(tert-butylaminocarbonyl)-(5 )-valylaminobutane (Phase 1) and (J )-l-(a-naphthyl)ethylaminocarbonyl-glycylaminobutane (Phase 2) are shown in Figure 8.1. Phase 1 was used for the enantioseparation of N-acetylamino acid methylesters and [R]- and (5)-4-nitrobenzoyl amino acids, but Phase 2 could not separate these enantiomers. The enantiomer selectivities of N-(5 )-l-(a-naphthyl)ethylaminocarbonyl-(5)-valylaminobutane (Phase 3), N-(5 )-l-(a-naphthyl)ethylaminocarbonyl-(P)-valylaminobutane (Phase 4), N-[R]-1-(oc-naphthyl)ethylaminocarbonyl-(R)-valylaminobutane (Phase 5), and N-[R)-l- a-naphthyl)ethylaminocarbonyl-(5 )-valylaminobutane (Phase 6), which all have two chiral centers, were examined by computational chemical analysis. The structures of model Phases 3-6 are also shown in Figure 8.1. 

Table 8.2 Separation factors and molecular properties of some N-acetylamino acid methylesters. a represents the separation factor, Eo the elution order, El the eluent (A=n-hexane/l,2-dichloromethane/ethanol 40 10 1 and B = n-hexane/l,2-dichloroethane/ethanol 100 20 1). The units for fs, he, es and vw are kcal mol. ...

Molecular properties of some N-acetylamino acid methylesters, some N-3,5-dinitrobenzoylamino acid methylesters, and their complexes with CRM 4. Reproduced by permission of Elsevier, ref. 29. 

A number of groups have shown how enantiomeric resolution of amino acids derivatized with non-chiral reagents is possible in SFC with chiral stationary phases. N-Acetylamino acid t-butyl ester racemates were rapidly resolved [17] on (N-formyl-L-valylamino)propyl silica with CO2 modified with methanol, acetonitrile and diethyl ether. A similar stationary phase allowed (18 rapid (< 5 min) separation of racemic N-4-nitrobenzoyl-amino acid isopropyl esto-s with methanol-modified CO2 the enantioselectivity in SFC was comparable with that in HPLC with isopropanol/n-hexane as mobile phase. Capillary column SFC on polysiloxane stationary phases containing chiral side chains has been employed... 

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