Valine ethyl ester

The p-nitrophcnyl ester prepared in part (e) is an active ester. The p-nitrophenyl group is a good leaving group and can be displaced by the amino nitrogen of valine ethyl ester to form a new peptide bond. 

An extension of this reaction leading to a general synthesis of N-substituted (3-lactams involves the addition of a primary amine to a freshly prepared solution of cyclopropanone, conversion of the resulting carbinol amine to the N-chloro derivative, and then decomposition of this intermediate with silver ion in acetonitrile. 87a> The method permits one to prepare N-substituted (3-lactams of great variety (Table 14), including those constructed from amino acid esters. 87b The use of valine ethyl ester (123) as a nitrogen source leading to 124 is illustrated. 

Name Carbonyl-b/s-(L-valine ethyl ester) Structure ... 

Phthaloylleucylvaline ethyl ester 710 DL-Valine ethyl ester hydrochloride (1.82 g, 10 mmoles) in dry tetrahydrofuran (20 ml) is treated at 0° with triethylamine (1.38 ml). The triethylamine hydrochloride is filtered off after an hour and washed well with tetrahydrofuran. Phthaloyl-leucine (2.57 g, 10 mmoles) is dissolved in the filtrate, and then at —8° dicyclohexylcarbo-diimide (2.26 g, 11 mmoles). The mixture is left for 2 h at — 5° and then at room temperature overnight. The separated 1,3-dicyclohexylurea is filtered off and the filtrate is evaporated in a vacuum, leaving a syrup which is dissolved in ethyl acetate (25 ml) and washed with 2n-hydrochloric acid (25 ml) and water (two 25-ml portions). The solution is dried over sodium sulfate, filtered, and evaporated in a vacuum, the residue (3.5 g, 90%) solidifying to a glass on storage this product is very soluble in alcohols, chloroform, ethyl acetate, pyridine, or dimethylformamide, moderately soluble in benzene or toluene, but insoluble in ether, light petroleum, or water. 

Valeric acid metal complexes geochemistry, 867 Valine ethyl ester... 

Draw the product formed when valine ethyl ester is treated with Sanger s reagent. 

More recently, binaphthyl fused with a furane ring ((/ )-( )[9,9 ]-bi[naphtho (2,l- )furanyl]-8,8 -diol) linked to a crown ether residue 20 was shown to be able to discriminate between enantiomers of phenylethylamine and valine ethyl ester by quenching, allowing calibration of the quenching effect as a function of enantiomeric composition [52]. 

It has been clearly shown in many detailed studies that the substitution of adjacent bulky side groups, for example, at the a-C position of amino acid esters, shields the polyphosphazene backbone from the attack of water molecules resulting in more hydrolytically stable polymers (Figure 2.7). This provides a very simple method to tailor the rate of degradation of amino-acid-ester-substituted polyphosphazenes. For example, the glycine ethyl ester derivative is reported to degrade in around 3 months (half-life), the alanine derivative in 6 months, whilst the valine ethyl ester requires approximately 1 year to reach this level of degradation [26]. 

An all-trons structure was assigned to poly(endo,endo-N,N-(norborn-5-ene-2,3-dicarbimido)-L-valine ethyl ester) (Scheme 8.11). Finally, Wagener et al. published details of the formal synthesis of poly(ethylene-co-vinyl alcohol), poly(ethylene-co-vinyl acetate), poly (ethylene-co-methylacrylate) and poly(ethylene-co-acrylic acid) copolymers, obtained via the ROMP of cyclooctene with hydroxy-, acetoxy-, methoxy-carbonyl and carboxylate-functionahzed cyclooctenes, followed by hydrogenation... 

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