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A -acylamino acids/esters

In the third transition state (TS3), the neutral catalyst is recovered by transferring the proton back from the catalyst to the substrate. In other words, the (former) azlactone ether oxygen atom deprotonates the tertiary ammonium ion. For proton transfer, again an LBHB is formed (N-0 distance 2.479 A, <(0,H,N)=166.2°). In the product complex, the catayst is neutral and the A-acylamino acid ester is bound in its iminol form to the catalyst (Product(iininol)). Finally, an additional 66.6 kJ moF are gained by the subsequent iminol-amide tautomerization (Product(ainide)) (Fig. 1). [Pg.10]

In addition, the use of an enantioselective or diastereoselective hydrolysis of racemic oxazolones offers another possibility to obtain new synthetic amino acids. Similarly, alcoholysis of 5(4H)-oxazolones gives the corresponding A -acylamino acid esters. [Pg.178]

Tajima obtained a-acylamino-a-alkoxy esters from a-acylamino acid esters reacting with DCCD/ROH (476). The intermediate azlactones underwent autoxidation which was followed by DCCD-supported hydroxy-alkoxy-exchange. An electrochemical synthesis of N-acyl-2-alkoxyproline derivatives was reported by Horikawa et al. (477). [Pg.299]

Alkylethers (269), R2 = alkyl, are obtained by the action of phosphorus pentasulfide on alkyl esters of a-acylamino acids (64, 334, 711) by means of the GabriePs synthesis (Section II.4), while aryl ethers (269), = aryl,... [Pg.304]

Enzymatic hydrolysis of A/-acylamino acids by amino acylase and amino acid esters by Hpase or carboxy esterase (70) is one kind of kinetic resolution. Kinetic resolution is found in chemical synthesis such as by epoxidation of racemic allyl alcohol and asymmetric hydrogenation (71). New routes for amino acid manufacturing are anticipated. [Pg.279]

Stannyl esters have been prepared to protect a -COOH group in the presence of an -NH2 group [( -Bu3Sn)20 or -Bu3SnOH, CgH, reflux, 88%]. Stannyl esters of A -acylamino acids are stable to reaction with anhydrous amines and to water and alcohols aqueous amines convert them to ammonium salts. Stannyl esters of amino acids are cleaved in quantitative yield by water or alcohols (PhSK, DMF, 25°, 15 min, 63% yield or HOAc, EtOH, 25°, 30 min, 77% yield). ... [Pg.442]

The use of homochiral complexation agents to separate the fluorine-19 chemical shifts of enantiomers containing fluorine has also been examined. Addition of the supported dipeptide 9 to a solution of the racemic iV-acylamino acid ester 10 in carbon tetrachloride leads to the appearance of two CF3 peaks corresponding to the two enantiomers. The separation is obviously concentration-dependent, but peak separation was sufficient for mixtures of enantiomers to give enantiomeric excesses comparable with those determined by gc analysis55. [Pg.280]

The synthesis of 5-alkoxyoxazoles (10) from acylated a-amino acid esters is analogous to the cyclization of a-acylamino carbonyl compounds (1). The reactions are usually carried out in the presence of phosphorus pentachloride or pentoxide in chloroform solution. [Pg.108]

K. Lloyd, G.T. Young, The use of acylamino acid-esters of 2-mercaptopyridine in peptide synthesis. J. Chem. Soc. Chem. Commun. 1968, 1400-1401 Amino acids and peptides. PartXXXrV. Anchimerically assisted coupling reactions the use of 2-pyridyl thiol esters. J. Chem. Soc. 1971,2890-2896 A.S. Dutta, J.S. Morley, Polypeptides. Part XII. The preparation of 2-pyridyl esters and their use in peptide synthesis. J. Chem. Soc. C. 1971, 2896-2900... [Pg.101]

Triethylamine (s. a, under MeS02Cl) a-Acylamino-a, -ethylenecarhoxylic acid esters... [Pg.243]

Reaction between amines and the reactive HPMA copolymers forms the basis for attachment of oligopeptide sequences, targeting residues or therapeutic agents to the polymer precursor (Fig. 3). Reaction of aliphatic amines (tertiary butylamine and diisopropylamine) in dimethylsulphoxide at 25 C with reactive copolymers containing different side-chains has been used to characterize copolymer reactivity.It has been shown that copolymers of HPMA with p-nitrophenyl esters of a-(acylamino) acids react faster with amines than copolymers with p-nitrophenyl esters of g-(acyl-amino) acids or, e-(acylamino) acids.21... [Pg.99]

Amino acid-based surfactants are derived from simple amino acids or mixed amino acids from synthesis or protein hydrolysates. They are composed of amino acid as the hydrophilic part and a long hydrocarbon chain as the hydrophobic part. The hydrophobic chain can be introduced through acyl, ester, amide, or alkyl linkage. Interest in amino acid surfactants is not new, as shown by early work in the area. In 1909, Bondi performed the first research on the introduction of a hydrophobic group to obtain A-acylgiycine and A-acyla-lamine [18], Subsequent work in this area focused on A-acylamino acids, as reported by Funk [19], Izar [20], Karrer [21], Staudinger and Becker [22],... [Pg.5]

Further work on the preparation of chiral a-amino-acids reported in the past year (see also the section on asymmetric hydrogenation) includes an extension of the utility of anions derived from lactim ethers (228) in the synthesis of such compounds by condensations with aldehydes and ketones chiral inductions are somewhat lower than in the alkylations of (228) reported previously (4, 320). Enzyme-mediated hydrolysis of 5(4H)-oxazolones by chymotrypsin or subtilisin gives a-acylamino-acids with good enantiomeric enrichments, especially if the substrate carries bulky substituents. Schiff s bases of a-amino-esters can be enriched enantiomerically to an extent of up to 70% by sequential deprotonation with a chiral lithium amide and protonation with an optically pure tartaric acid. ... [Pg.143]


See other pages where A -acylamino acids/esters is mentioned: [Pg.576]    [Pg.79]    [Pg.576]    [Pg.79]    [Pg.270]    [Pg.333]    [Pg.21]    [Pg.215]    [Pg.647]    [Pg.303]    [Pg.523]    [Pg.237]    [Pg.105]    [Pg.186]    [Pg.10]    [Pg.14]    [Pg.16]    [Pg.127]    [Pg.94]    [Pg.98]    [Pg.360]    [Pg.94]    [Pg.207]    [Pg.234]    [Pg.548]    [Pg.292]    [Pg.83]    [Pg.218]    [Pg.216]    [Pg.385]    [Pg.229]    [Pg.171]   
See also in sourсe #XX -- [ Pg.94 , Pg.97 , Pg.98 , Pg.107 , Pg.109 , Pg.117 , Pg.274 , Pg.360 , Pg.362 ]




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