Amino N-acetylated

SYNS -ACETYL-N -METHYL-4 -AiMINO-N,N-DIMETHYL-4-AMINOAZOBENZENE 4-(N-ACETYL-N-METHYL)AMINO-4 -(N, N -DIMETHYL. MINO)-AZO-BENZENE N, N -DIMETHYL-4 -AMINO-N-ACETYL-N-MONOMETHYL-4-AMINOAZOBEKZENE N-(4-((4-(DIMETHYL. MINO)PHENYL)AZO)PHENYL)-N-METHYLACETAMIDE... 

N, N -DIMETHYL-4 -AMINO-N-ACETYL-N-MONOMETHYL-4-A. nNOAZOBENZENE see DPQ200... 

Acetyl-a-amino-n-butyric acid [34271-24-4] M 145.2, pK 3.72. Crystd twice from water (charcoal) and air dried [King and King J Am Chem Soc 78 1089 7956]. 

A recent report describes the conversion of A-formyl- and N-acetyl-L-leucine into optically active azlactones with dicyclohexyl-carbodiimide (DCC) [Eq. (29)]. Other cyclization reagents, e.g. acetic anhydride, POCI3, SOCI2, and polyphosphoric acid, cause racemiza-tion. These azlactones react with optically active amino acid esters to give esters of dipeptides with retention of activity. 

Derivatives of nalidixic acid (69a-69d), containing an amino or acetyl-amino substituent at position 7 and an alkyl group at N-1, were successfully nitrated to give (70a-70d). However, in all cases hydrolysis of the amino and acetylamino group was observed (79YZ155 80CPB235). 

Amino sugars, such as o-glucosamine, have an OH group leplaced by an -NH2. The N-acetyl amide derived from o-glucosamine is the monosaccharide unit from which chitm, the hard crust that protects insects and shellfish, is made. Still otheramino sugars are found in antibiotics such as streptomycin and gentamicin. 

Several L-amino acids are produced on a large scale by enzymatic resolution of N-acetyl-D,L-amino adds (Figure A8.4). Acylase immobilised on DEAE-Sephadex is for example employed in a continuous process while Degussa uses the free acylase retained in a membrane reactor. In the latter process the advantage of reuse of the enzyme and homogeneous catalysis are combined. 

D, L-N-acetyl amino acid L-amino acid D-N-acatyl amino acid... 

Figure A8.4 Commercial process for the enzymatic production of L- and D-amino acids from N-acetyl-D,L-amino acids.

Microbial serine proteases, such as chymotrypsin, catalyse the hydrolysis of N-acetyl-L-amino add esters (Figure A8.ll). 

Figure A8.11 Enzymatic resolution of N-acetyl-D,L-amino add esters.

Tylenol paracetamol N-acetyl-para-aminophenol para-acetyl-amino-phenol... 

Silica gel [11] or alumina [11a, 12] alone, or silica and alumina together modified by Lewis-acid treatment [13] and zeolites [14], have been widely used as catalysts in Diels-Alder reactions, and these solids have also been tested as catalysts in asymmetric Diels-Alder reactions [12,13b,14]. Activated silica gel and alumina at 140 °C were used [15] to catalyze the asymmetric cycloaddition of (-)-menthyl-N-acetyl-a, S-dehydroalaninate (3) (R = NHCOMe) with cyclopentadiene in the key step for synthesizing optically active cycloaliphatic a-amino acids. When the reactions were carried out in the absence of solvent, a higher conversion was obtained. Some results are reported in Table 4.5 and compared with those obtained by using silica and alumina modified by treatment with Lewis acids. Silica gel gives a reasonable percentage of conversion after 24 h with complete diastereofacial selectivity in exo addition. 

In a first report [24], the enantioselectivities of various proteases were evaluated by comparing the biocatalyzedhydrolysis of2-chloroethyl esters of N-acetyl-i- and D-amino acids in water and their transesterification with w-propanol in butyl ether. By comparing the ratio of the kc t/Ku values for the l- and D-enantiomers in the two reactions, a remarkable relation of the proteases enantioselectivity was observed apparently, in this case, the organic solvents destroyed the selectivity of the tested enzymes. This finding... 

Recently, a very interesting preparation of P-peptides has been carried out by Kanerva and coworkers through a two-step lipase-catalyzed reactions in which N-acetylated P-amino esters were first activated as 2,2,2-trifluoroethyl esters with CALB [55]. The activated esters were then used to react with a P-aminoester in the presence of CALA in dry diethylether or diisopropylether (Scheme 7.31). In this peptide synthesis, the aminoester was used in excess and the unreacted counterpart was easily separated and later recyded. 

Aminoglycoside antibiotics la 107,270, 284,354,380,423,434 Amino groups lb 194 4-Aminohexoses, N-acetyl derivatives lb 233... 

A substantial number of bioactive molecules, such as polypeptides, N-acetyl-DL-penicillamine, p-(dipropylsulfamoyl)benzoic acid, and nicotinic acid, contain a carboxylic acid function, and this provides a site for linkage to a polyphosphazene chain. A number of prototype polymers have been synthesized in which pendent amino groups provide coupling sites for the carboxylic acid (34). The amide linkages so formed are potentially bioerodible, but the use of a hydrolytic sensitizing cosubstituent would be expected to accelerate the process. 

Figure 13-10. Glucosamine (2-amino-D-glucopyra-nose) a form). Galactosamine is 2-amino-D-galactopy-ranose. Both glucosamine and galactosamine occur as N-acetyl derivatives in more complex carbohydrates, eg, glycoproteins.

Among the spectroscopic methods applicable to polysaccharides, u.v. spectrophotometry is of little value for characterizing heparin, whose main, electronic chromophore (the C02 group) displays a band at 220 nm, that is, in a region where all glycosaminoglycans absorb (also through their N-acetyl chromophores), and where minor proportions of unsaturated or aromatic contaminants cause serious interference.77 With pure heparin preparations, the carboxylate chromophore is most useful for chiroptical measurements, and a semi-quantitative evaluation of the extent of N-acetylation of 2-amino-2-deoxy-D-glucose residues is also possible.78... 

The amino sugar counterparts of D-glucuronic acid and nonsulfated L-iduronic acid in heparin are either N-acetylated, or nonsulfated at C-6, or both. 2-Acetamido-2-deoxy-D-glucosyl residues account for only a minor proportion of the total hexosamine in heparin, and are especially low in beef-lung preparations (see Table II).8,138,147 -149 In contrast, they... 

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