Acids V-acylamino

TABLE 7.21 V-ACYLAMINO ACID ESTERS FROM ALCOHOLYSIS OF SATURATED 5(4//)-OXAZOLONES, 181... 

A method that has been used to approach 100% theoretical yield in asymmetric syntheses is dynamic kinetic resolution, or DKR. Although this method has been practiced based on strictly chemical reactions, only those chemoenzymatic DKR reactions will be discussed here. Most often, the enzyme used by this method is a hydrolase (lipase, esterase, protease), but other enzymes such as hydantoinases, /V-acylamino acid racemases, and dehydrogenases have also been exploited to effectively carry out DKR reactions.196 For additional details the reader is directed to the many review articles written on DKR.197 206... 

A more important cause of enantiomerisation stems (Scheme 7.10) from the cyclisation of carboxy-activated derivatives of -/V-acylamino acids including peptides (7.55) to form a 5(4)-oxazolone (7.56) concurrently with the formation of a coupled product (7.55—>7.60) Enolisation of the 5(4H)-oxazolone (7.56 = 7.57 7.58) destroys the chirality and the rate of enantiomerisation depends on the... 

Dehydration of (V-acylamino-acids generates azlactones these are in equilibrium with mesoionic species, which can be trapped by reaction with alkynes, final loss of carbon dioxide giving the aromatic pyrrole. 

The V-acylamino-acid-releasing enzyme (Takara Shuzo Co., Ltd., Tokyo, Japan) liberates the V-terminal acylamino acid from V-acylated peptides (Tsunasawa and Narita, 1976). An V-terminal triptic peptide with a blocked V-terminus was dissolved in 10 pi of 15 mM sodium phosphate buffer (pH... 

In the last decade, many efforts have been devoted to the study of the influence of chiral molecules on the enzymatic processes at the membrane surfaces. V -Acyl-L-and D-amino acid derivatives have been employed as model substances for simulating biomembranes and interfacial processes at biomembrane surfaces [32]. It has been found that chiral monolayers of V -acylamino acid methyl esters on a pure water surface showed that hydrogen bond formation via NH, COOH, and p-hydroxyphenyl groups (i.e., tyrosine side chains) lead to a pronounced chiral discrimination [33,34]. Homochiral (d-d or L-L interactions) and heterochiral (d-l interaction) discrimination can be observed depending on the area per molecule ( min)> which depends on the conformation of the amino acid residue and on the alkyl chain length. 

NL Benoiton, YC Lee, FMF Chen. Studies on asymmetric induction associated with the coupling of iV-acylamino acids and /V-ben/.yloxycarbonyldi peptides. Ini J Pent Prot Res 38, 574, 1991. 

Br prevents side reactions and makes BiBr3 a better Lewis acid catalyst, which is in accordance with our work BiBr3 affords only Ritter reaction products in the high dielectric constant solvent CH3CN, while BiCl3 originates a mixture of both v7 -/V-acylamino-hydroxy compounds and chlorohydrins. 

V-Alkyl- and JV-aryl-a-acylamino acids with a mixture of acetic anhydride and perchloric acid form 1,3-oxazolonium perchlorates... 

The 2,6-dichloropyridine /V-oxidc-Ru(IV)(TMP)Cl2 (TMP = tetramesitylporphy-rinato) system converts /V-acyl cyclic amines to N-acylamino acids via oxidative C-N bond cleavage. The kinetic isotope effect was measured using N-benzoyl [2,2-di Ipyrrolidine. The intramolecular kinetic isotope effect in the oxidation of was found to be 9.8 0.2, strongly suggesting that the rate-determining step is hydrogen abstraction and not one-electron oxidation.75... 

Routes to 4/7-1,3-oxazines and 4/7-1,3-thiazines involve the cyclization of amides or thioamides with acidic reagents or the appropriate sulfur atom donor (e.g., Scheme 163) <1978AHC(23)1, CHEC-III(8.08.9.6)594>. For example, thionation of 3+V-acylamino ketones 353 with Lawesson reagent (LR) gives the intermediate 3-A-thioacylamino thiones which cyclize to the 1,3-thiazines 354 with loss of H2S (Scheme 164) <2001HCA2347>. 

Various trpentadienoic acids (57) by the mixed anhydride method (equation 37). The procedure is reproducible when V,V-diisopropylethyl-amine is used in place of triethylamine. 

Mixed Anhydride Coupling. This very popiilar method, involving the use of alkyl chloroformates as reagents to make anhydrides v/ith acylamino acids or acylpeptides, has been reinvestigated. Determann, Heuer, Pfaender and Reinartz o have shown that exposinre of the mixed anhydride... 

An important variation of the Perkin reaction is the Erlenmeyer azalactone synthesis exemplified by equation (4), involving condensation of an aldehyde and an /V-acylglycine derivative in the presence of acetic anhydride and sodium acetate.6 Although this reaction, analogous to the classical Perkin condensation, was initially limited to the use of aromatic aldehydes, Baltazzi and Robinson reported31 that the use of lead acetate and THF allowed the preparation of several azalactones derived from aliphatic aldehydes (equation 15). The results for the condensation of several aldehydes and ketones with hippuric acid (28) under these conditions are shown in Table 2. The reaction proceeds through the intermediate (26) (intramolecular condensation of 25), which reacts with the aldehyde in Perkin fashion to provide the so-called azalactone product (Scheme 8). It is the formation of such oxazolones from acylamino acids which is be-... 

The catalyst for cleavage of peptide deformylase was searched with a library of catalyst candidates synthesized by the Ugi reaction (Scheme 2) (134). In this multicomponent condensation reaction, the mixture of a carboxylic acid, an amine, an aldehyde, and an isocyanide produces an iV-acyl amino acid amide. The catalyst candidates, therefore, are iV-acylamino acid amides containing various polar and nonpolar pendants as well as the Co(III) complex of cyclen. The Co(III) complex of cyclen (135) was chosen as the proteolytic center in view of the results described in Section V.A. Cyclen with three secondary amines protected with ferf-butyloxycarbonyl (t-boc) groups was incorporated in either the carboxyl or the amine component of the Ugi reaction. Later, the t-boc groups were removed and Co(III) ion was inserted to the cyclen portion. 

The acylase-catalyzed resolution of /V-acetyl-DL-amino acids is a key commercial process. The racemization of the remaining /V-acetyl-D-amino acid after separation of the L-amino acid must be performed, but adds complexity and cost. Therefore, in situ racemization with a racemase possessing specificity for N-acylamino acids without affecting the stereochemistry of the product L-amino acids is very desirable. The pentameric enzyme from Streptomyces sp. Y-53 specifically catalyzes the racemization of N-acylamino acids without acting on amino acids [182],... 

Bondi reported the first research on tV-acylamino acid in 1909 [5], in it he synthesized lipoamino acid from glycine and alanine as a form of V-lauroyl-amino acid. In that research, Bondi speculated that the necrosis of fat in the cell should be attributed to the decomposition of acylamino acid to amino acid and fatty acid. To elucidate this theory, he studied the biodegradation of synthesized acylamino acids. Since then, research into acylamino acids has appeared periodically in the journals, with two aspects of interest one is the investigation of natural existence, and the other is to explore the functionality of such molecules. 

Lipoamino acids are also particularly attractive as antiviral agents. Certain acylamino acid derivatives have been found to produce inhibition on influenza neuraminidase [30]. A number of V -palmitoylated amino acids/peptides have been incorporated into model membranes affecting the transition temperature between the bilayer to hexagonal aggregation, a property associated with antiviral activity. Epand et al. [31] demonstrated the inhibition action of A -palmitoyltryptophan against the Cantell strain of Sendai virus (parainfluenza type 1). 

V-[2-(Acylamino)phenyl]-A-alkylarylamincs 1 cyclize in phosphoryl chloride or in polyphos-phoric acid to the dibenzodiazepines 2. Selected example are given, exact yields were not reported.44 309... 

G. P. Smirnova, N. V. Chekareva, O. S. Chizhov, B. M. Zolotarev, and N. K. Kochetkov, Mass spectrometry of sialic acids Peracetylated methyl esters of 5-acylamino-3,5-dideoxy-nononic and -heptonic acids, Carbohydr. Res., 59 (1977) 235-239. 

Benzamidinc combines with 2-amino-3-phenacyl-l,3,4-oxadiazolium bromides to give l-acylamino-2-benzimidoylamino-4-arylimidazolcs. Yields arc only moderate (14-43%), but the reaction works for a variety of 4-arylimidazoles f22. Reactions of /V-methyl-JV-(JV -phenylbenzimidoyl)amino-acetonitrile (13) under acidic conditions lead to imidazolium salts which have amino (14) or amido (15) groups in the 4-position (Scheme 2.2.6). The 4-amino salt (14) undergoes Dimroth rcaaangement to the 4-phenylaminoimidazole (16) direct conversion of (13) into (16) also occurs in warm alkali [8]. A Claisen rearrangement of the adduct (17), which forms from interaction of an arylamidoxime and a propiolate ester, provides a method... 

---