Esters amino acid

There are a few documented examples of studies of ligand effects on hydrolysis reactions. Angelici et al." investigated the effect of a number of multidentate ligands on the copper(II) ion-catalysed hydrolysis of coordinated amino acid esters. The equilibrium constant for binding of the ester and the rate constant for the hydrolysis of the resulting complex both decrease in the presence of ligands. Similar conclusions have been reached by Hay and Morris, who studied the effect of ethylenediamine... 

Simple esters cannot be allylated with allyl acetates, but the Schiff base 109 derived from o -amino acid esters such as glycine or alanine is allylated with allyl acetate. In this way. the o-allyl-a-amino acid 110 can be prepared after hydrolysis[34]. The Q-allyl-o-aminophosphonate 112 is prepared by allylation of the Schiff base 111 of diethyl aminomethylphosphonates. [35,36]. Asymmetric synthesis in this reaction using the (+ )-A, jV-dicyclohex-ylsulfamoylisobornyl alcohol ester of glycine and DIOP as a chiral ligand achieved 99% ec[72]. 

Aluminum chloride [7446-70-0] is a useful catalyst in the reaction of aromatic amines with ethyleneknine (76). SoHd catalysts promote the reaction of ethyleneknine with ammonia in the gas phase to give ethylenediamine (77). Not only ammonia and amines, but also hydrazine [302-01-2] (78), hydrazoic acid [7782-79-8] (79—82), alkyl azidoformates (83), and acid amides, eg, sulfonamides (84) or 2,4-dioxopyrimidines (85), have been used as ring-opening reagents for ethyleneknine with nitrogen being the nucleophilic center (1). The 2-oxopiperazine skeleton has been synthesized from a-amino acid esters and ethyleneknine (86—89). 

The history of the discovery of amino acids is closely related to advances ia analytical methods. Initially, quantitative and qualitative analysis depended exclusively upon crystallization from proteia hydrolysates. The quantitative precipitation of several basic amino acids including phosphotungstates, the separation of amino acid esters by vacuum distillation, and precipitation by sulfonic acid derivatives were developed successively duriag the last century. 

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. 

Reaction with Phosgene. This reaction of amino acid esters is used for preparing the corresponding isocyanates, especially lysine diisocyanate [4460-02-0] (LDI). LDI is a valuable nonyellowing isocyanate with a functional side group for incorporation in polyurethanes. 

Formation of Diketopiperazines. Esters of a-amino acids can be readily prepared by refluxing anhydrous alcoholic suspensions of a-amino acids saturated with dry HQ. Diketopiperazines are formed by heating the alcohohc solution of the a-amino acid ester. 

Currently available proteins are all deficient to greater or lesser extent in one or more of the essential amino acids. The recently advanced plastein reaction (229) has made it possible to use protein itself as substrate and to attach amino acid esters to the protein with high efficiency. By this method, soy bean protein (which is deficient in methionine) has been improved to the extent of having covalently attached L-methionine at 11%. 

An unusual approach to the lumazine nucleus was found in the photochemical transformation of 6-azido-l,3-dimethyluracil (289) with various amino compounds (78JA7661). Irradiation of (289) in the presence of ethyl a-amino acid esters forms 7-substituted 7,8-dihydrolumazin-6-ones (288), and with a-aminoketones 6-substituted 7,8-dihydro-lumazines (290) are formed (equation 103). 

The piperonyl ester can be prepared from an amino acid ester and the benzyl alcohol (imidazole/dioxane, 25°, 12 h, 85% yield) or from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 57-95% yield). It is cleaved, more readily than a p-methoxybenzyl ester, by acidic hydrolysis (CF3COOH, 25°, 5 min, 91% yield). ... 

Phenylhydrazides have been prepared from amino acid esters and phenylhydrazine in 70% yield they are cleaved by oxidation [Cu(OAc)2, 95°, 10 min, 67% yield FeCyi NHCl, 96°, 14 min, 85% yield ]. 

HCO2H, DCC, Pyr, 0°, 4 h, 87-90% yield. These conditions produce N-formyl derivatives of r-butyl amino acid esters with a minimum of race-mization. -... 

This vinylogous amide has been prepared in 70% yield to protect amino acid esters. It is cleaved by treatment with either aqueous bromine or nitrous acid (90% yield). ... 

These transition metal carbenes, prepared in 66-97% yield from amino acid esters, are cleaved by acid hyrolysis (CF3CO2H, 20°, 80% yield 80% AcOH M = W, BBr3, -25°). ... 

The advantages of the methoxyethyl ester over some of the other water-solubilizing esters are that many of the amino acid esters are crystalline and thus easily purified, are cleaved with a number of readily available lipases, and are useful for the synthesis of A-linked glycopeptides. ... 

The piperonyl ester can be prepared from an amino acid ester and the benzyl alcohol (imidazole/dioxane, 25°, 12 h, 85% yield) or from an amino acid and the... 

Phenylhydrazides have been prepared from amino acid esters and phenylhy-drazine in 70% yield. ... 

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. 

Conjugate addition of strong nucleophiles to the >C=N—C=C< moiety, followed by ring opening of the resulting saturated 5 4H)-oxazolone. Thus, 57 reacts with simple or peptidic amino acid esters [Eq. (31)]. Similarly, 62 gives 63 in methanolic 7i-propylamine, and... 

PclCOi-cdidlyzed subsdnidoa reacdoa, a aovel, mild reducdoa of a-nitro ester to an amino acid ester withTiCU, and an improved procedure for nracil ring formadon. 

D, L-amino acid ester L-amino acid D-amino acid ester... 

Simple aromatic acids Some amino acid esters... 

Hayama et al.132 discussed the catalytic effects of silver ion-polyacrylic add systems toward the hydrolyses of 2,4-dinitrophenylvinylacetate 84 (DNPVA) by using the weak nudeophilicity of carboxylic groups and the change-transfer interactions between olefinie esters and silver ions133Metal complexes of basic polyelectrolytes are also stimulating as esterase models. Hatano etal. 34, 13S) reported that some copper(II)-poly-L-lysine complexes were active for the hydrolyses of amino acid esters, such as D- and L-phenylalanine methyl ester 85 (PAM). They... 

Waldmann H., Braun M. Amino Acid Esters As Chiral Auxiliaries in Asymmetric Cycloadditions Gazz. Chim. Ital. 1991 121 277-284... 

Oxazolones (azlactones) are a form of activated lactones, so they are included in this section. CAL-B is an effective catalyst for the DKR of various racemic four-substituted-5 (4H)-oxazolones, in the presence of an alcohol, yielding optically active N-benzoyl amino acid esters as illustrated in Figure 6.24 [40]. Enantioselective biotransformations of lactides [72,73] and thiolactones ]74] have also been reported. 

Allcock HR, Shawn R, and Scopelianos AG. Poly [(amino acid ester) phosphazenes] as substrates for the controlled release of small molecules. Biomaterials, 1994, 1, 5563-5569. 

---