Alanine Ester Research Articles

Asymmetric Synthesis of α‐Methyl α‐Amino Acids by Diastereoselective Alkylation of Optically Active 6‐Isopropyl‐3‐methyl‐2,3—dihydro‐6H‐1,4‐oxazin‐2‐ones

At room temperature already highly diastereoselective alkylation of the new, cyclic, chiral alanine ester derivatives (6R)-1 can been achieved with either K2CO3 as base under solid–liquid phase-transfer catalysis or Pd catalysis unter neutral conditions. The products (3S,6R)-2 can be easily hydrolyzed to form (S)-α-methyl α-amino acids.

Chemical properties ofN-(amidomethy)- andN-(imidomethyl)glycine derivatives 2. Reactions at alkoxycarbonyl and carboxyl groups

N-(Aroylarnmomethylfglycine amides were synthesized by reactions ofN-(aroyllminomethyl) glycine esters with ammonia. Alkaline hydrolysis ofN-(amidomethyl)glycine,N-(irnidornethyl)glycine, andN-(amidomethyl)pheriylalariiiie esters afforded the correspondingN-(amidowthyVa-amirio acids- Reactions of the Last-mentioned compounds with ethyl esters of glycine, alanine, and phenylalanine in the presence of dicyclohexylcarbodiimide yielded dipeptides containingNh-amidomethyl substituents.

Anti‐Selective Aldol Reactions of Amino Acid Ester Enolates. Application to the Synthesis of α‐Alkylated β‐Hydroxy Amino Acids

AbstractDeprotonation of N‐protected esters of the amino acids alanine 1, ethylglycin 6, valine 7, and phenylalanine 8 with LDA and subsequent addition of various metal salts result in the formation of a probably chelated metal enolate. Aldol reactions of these enolates with aldehydes afford the anti isomers of α‐alkylated α‐amino‐β‐hydroxy acids in a highly diastereoselective fashion. Best results are obtained with titanium enolates, bulky aliphatic aldehydes, and sterically demanding amino acids.

Synthesis ofN-(amidomethyl)- andN- (imidomethyl)-?-amino acid esters by reactions of ?-amino acid esters with formaldehyde and amides or imides

Reactions of hydrochlorides of glycine, alanine, phenylalanine, L-isolcucinc, and L-valine esters with aromatic and heteroaromatic carboxamides afforded hydrochlorides of the correspondingN-(amidomethyl)-α-amino acid esters.N-(Phthalimidomethyl)-α-amino acid esters were obtained by reactions of α-amino acid esters containing free amino groups with formaldehyde and phthalimide, The1H NMR studies demonstrated that the chiral centers of α-amino acids may be retained in the course of condensation. Reactions of the Mannish bases obtained and their hydrochlorides with acetic anhydride and tosyl chloride afforded the correspondingN-aryl andN-sulfonyl derivatives.

ESR Spectra of Some Amino Acid Derivatives of Semiquinone Anions

Reaction of then-butyl esters of alanine and leucine with bothtert-butyl-1,4-benzoquinone and 1,4-naphthoquinone gave the correspondingN-substituted quinones. Substitution at both C-5 and C-6 was observed with 2-tert-butyl-1,4-benzoquinone, but C-6 substitution predominated. Reduction of the latter isomers and of the naphthoquinones gave ESR spectra to which splitting constants were assigned with the help of ENDOR spectroscopy and selective deuteration.

Significant Enantioselectivity in Alanine Ester Hydrolysis Catalyzed by Imidazole Attached β-Cyclodextrins

Abstract Imidazole-appended β-cyclodextrins, 3-deoxy-3-imidazolyl-β-cyclodextrin (3Im-βCyD) and 6-deoxy-6-imidazolyl-β-cyclodextrin (6Im-βCyD) were synthesized as substrate selective enzyme mimics. 6Im-βCyD shows marked enantioselectivity in the hydrolysis of Boc-alanine p-nitrophenyl ester rather than 3Im-βCyD. This selectivity could be interpreted by transition stability theory.

Molecular arrangement and polycondensation of octadecyl esters of aromatic amino acids in Langmuir-Blodgett films

The molecular arrangements and polycondensation of octadecyl esters of phenylalanine ( L-PheC18), tyrosine ( L-TyrC18) and tryptophan ( L-TrpC18) in Langmuir-Blodgett (LB) films were studied. These LB films adopt good layer structures: the long hydrocarbon chains stand nearly vertical to the film plane; the benzene ring of L-PheC18 lies almost flat; and the phenol group of L-TyrC18 and the indole ring of L-TrpC18 are oriented fairly perpendicular to the film plane. It has been found that the polycondensation is accelerated by regular arrangements of monomer molecules in the LB films, where functional groups can be concentrated in the two-dimensional plane and situated more effectively for the reaction than in the bulk solids or the molten states. The reaction rates in the LB film decreased in the order L-TyrC18 > L-TrpC18 > L-PheC18, which can be ascribed to their distinct steric hindrances caused by the different orientations and sizes of the aromatic rings. Polycondensation in LB films can be improved by mixing them with octadecyl esters of alanine to reduce steric hindrances. The resultant polypeptides take mainly the α-helix conformation.

Isomalto-oligosaccharide-containing lipoteichoic acid of Streptococcus sanguis. Microheterogeneity and distribution of chain substituents.

The lipoteichoic acid of Streptococcus sanguis DSM 20567 contains a poly(glycerophosphate) chain, with 49% of the glycerophosphate residues being substituted with D-alanine ester, 35% with alpha-D-glucopyranosyl and alpha-isomalto-oligosaccharide residues. Analysis of molecular species by affinity chromatography on concanavalin A showed all chains to be substituted and alanine ester and glycosyl residues to be present on the same rather than on separate chains. Molecular species varied in the length of the poly(glycerophosphate) chain, the extent of glycosylation, and had a constant alanine-ester content. An alkali-hydrolysis procedure revealed a distribution pattern between random and regular for the glycosyl substituents and suggested a similar distribution for the alanyl residues which occupy the free positions between the glycosyl substituents.

Molecular Analysis of Lipid Macroamphiphiles by Hydrophobic Interaction Chromatography, Exemplified with Lipoteichoic Acids

Analyzed were (I) the oligoglucosyl-, alanyl-substituted poly(glycerophosphate) lipoteichoic acid of Enterococcus hirae containing Glc(α1-2)Glc(α1-3)acyl 2-Gro and a phosphatidyl derivative thereof as lipid anchor, (II) the poly(digalactosyl, galactosylglycerophosphate) lipoteichoic acid of Lactococcus garvieae containing the same glycolipid and an acyl derivative of it, and (III) the N-acetylglucosaminyl-, alanyl-substituted poly(glycerophosphate) lipoteichoic acid of Staphylococcus aureus with Glc(β1-6)Glc(β1-3)acyl 2Gro as the sole lipid moiety. Hydrophobic interaction chromatography on octyl-Sepharose separated lipoteichoic acids I and II into two peaks according to the number of fatty acids. Within each peak further fractionation occurred in the order of decreasing length of the hydrophilic chain. A similar fractionation was observed within the single peak of lipoteichoic acid III. With lipoteichoic acid I and III the extent of glycosylation decreased with decreasing length of the hydrophilic chain whereas the content of alanine ester remained either constant or increased. Variations in the oligosaccharide pattern of lipoteichoic acid I and in the fatty acid composition of all lipoteichoic acids could also be observed. Collectively, the data provide for the first time a detailed picture of the complex polydispersity of lipoteichoic acids comprising the number of fatty acids, the length of the hydrophilic chain, the kind and extent of chain substitution, and the fatty acid composition. The procedure will also be applicable to the molecular analysis of lipopolysaccharides and bacterial lipoglycans. Moreover, the results are of physicochemical interest because they demonstrate for lipid macroamphiphiles an inverse relationship between hydrophobicity and the size of the hydrophilic headgroup.

Investigation of the effect of acylation on the enantiomeric separation of amino acid isopropyl esters by gas chromatography

The effects of acylation on the enantiomeric separation of isopropyl esters of alanine, valine, allo-isoleucine, isoleucine, leucine and aspartic acid were investigated with a cross-linked polycyanoethyl vinyl siloxane- l-Val- tert-butylamide fused-silica capillary column. The gas chromatographic behaviour of N-formyl, N-acetyl, N-trifluoroacetyl and N-benzoyl derivatives of the amino acid isopropyl esters were studied. The chiral recognition mechanism of the solutes on diamide chiral stationary phases is discussed.

Photochemistry of N ‐Phthaloyl α‐Amino Acid Esters: A New Approach to β,γ‐Unsaturated α‐Amino Acid, Dihydrobenzazepinedione, and Pyrrolizidinone Derivatives

The N-phthaloyl-α-amino acid methyl esters of 2-aminobutyric acid (2a), valine (2b), norvaline (2c), tert-leucine (2d), isoleucine (2e), allo-isoleucine (2f), leucine (2g), methionine (2h), alanine (2i), and phenylalanine (2k) were synthesized in enantiomerically pure form via the N-phthaloyl-α-amino acids (1a–k), and their photochemistry was studied. Except 2i and 2k, which proved to be photostable, all compounds were converted into three types of products, depending on the substitution pattern: a) isomerization products (derivatives of β,γ-unsaturated α-amino acids) 3a, b, c, and e, b) ring expansion products (benzazepinedione esters) 4a and c, and c) cyclization products (5d from the tert-leucine derivative 2d). High diastereoselectivities (d.r. > 95:5) were observed for all reactions except the transformations of the 2-aminobutyric acid derivative 2a. The absolute configuration of the α-stereogenic center was retained during photolysis, as proven for the isode-hydrovaline (type a product) 3b. PCC oxidation (to give 7b) and hydrogenation afforded 2b with an optical rotation comparable to the starting material. Treatment of 3b with an acid or a base led to epimerization (3b′) or isomerization of the C = C bond (6b), respectively. The diastereomeric dihydrobenz-azepinedione esters 4a, b were formed with d.r. = 33:67 (cis: trans) and in 60% yield during photolysis of 2a. The isoleucine derivative 2e, however, was converted into the cis isomer 4a with high diastereoselectivity (d.r. >95:5), whereas the corresponding allo substrate 2f was only converted into the trans-isomer 4b. Ethylene was extruded during irradiation of the latter substrates and during irradiation of the norvaline derivative 2c, whereas propene extrusion from the leucine derivative 2g led to the formation of the unsubstituted type b product 4c. The methionine derivative 1h was the only N-phthaloylamino acid which did not show photodecarboxylation, instead two ζ-hydrogen abstraction products were formed: the hydroxy acid 9h and the tetracyclic lactone 10h. The methionine ester 2h was only converted into the ring expansion products 11h, h′ presumably by a photo electron transfer step. The chronology of the double hydrogen transfer reaction (γ- followed by δ-H abstraction, leading to type a products) was determined by using the deuterium labeled compound (±)[3–D1]-2b.

X=Y-ZH Systems as potential 1,3-dipoles. Part 39. Metallo-azomethine ylides from aliphatic aldimines. Facile regio- and stereo-specific cycloaddition reactions

Aliphatic aldimines of alanine ester, a thiolactone and a lactam undergo AgOAc catalysed regio- and stereo-specific endo-cycloaddition to dipolarophiles whilst LiBr leads mainly to Michael adducts. Metalloazomethine ylide formation occurs stereospecifically in toluene but, in the case of alanine ester aldimines, stereoselectively in acetonitrile.

Enzymatic enantioselective ester hydrolysis by carboxylesterase NP

AbstractThe enzymatic hydrolysis of a series of carboxylic esters by carboxylesterase NP has been investigated in order to determine the scope and limitations of this enzyme. 2‐Substituted propionates were hydrolyzed with high enantioselectivity when an aromatic moiety was part of the 2‐substituent. Enantioselective hydrolysis could be accomplished with several 2‐arylpropionates, 2‐(aryloxy)propionates and N‐arylalanine esters. The propionate esters yielded propionic acids as (S) enantiomers, whereas the alanine esters yielded the (R) enantiomers. Without a 2‐aryl substituent, the enzymatic hydrolysis of the propionates occurred at a lower rate without acceptable enantioselectivity. In addition to 2‐substituted propionates, only a few other esters were hydrolyzed with high enantioselectivity by carboxylesterase NP, such as some prochiral disubstituted malonates. 1‐Phenylethyl acetate was the only substrate with chirality in the alcohol part of the ester that was found to be hydrolyzed enantioselectively.Carboxylesterase NP proved to be a powerful enzyme for kinetic resolution of propionate esters with an aromatic ring containing a 2‐substituent.

Separation of the poly(glycerophosphate) lipoteichoic acids of Enterococcus faecalis Kiel 27738, Enterococcus hirae ATCC 9790 and Leuconostoc mesenteroides DSM 20343 into molecular species by affinity chromatography on concanavalin A

This study shows for the first time microheterogeneity of 1,3-linked poly(glycerophosphate) lipoteichoic acids. The lipoteichoic acids investigated were those of Enterococcus faecalis Kiel 27738 (I), Enterococcus hirae (Streptococcus faecium) ATCC 9790 (II), and Leuconostoc mesenteroides DMS 20343 (III). Lipoteichoic acids II and III are partially substituted by mono-, di-, tri-, and tetra-alpha-D-glucopyranosyl residues with (1----2) interglycosidic linkages. Lipoteichoic acid I is substituted with alpha-kojibiosyl residues only. Lipoteichoic acids I and III additionally carry D-alanine ester. Lipoteichoic acids were separated on columns of concanavalin-A-Sepharose according to their increasing number of glycosyl substituents per chain. It was evident that all molecular species are usually glycosylated and that alanine ester and glycosyl residues occur on the same chains. The chain lengths of lipoteichoic acid I and II vary between 9-40 glycerophosphate residues, whereas those of lipoteichoic acid III appear to be uniform (33 +/- 2 residues). Molecular species differ in the extent of glycosylation but their content of alanyl residues is fairly constant. All lipoteichoic acids contain a small fraction (5-15%) different in composition from the bulk and most likely reflecting an early stage of biosynthesis. Two procedures for chain length determination of poly(glycerophosphate) lipoteichoic acids are described.

A 28 kDa protein of normal mouse serum binds lipopolysaccharides of Gram-negative and lipoteichoic acids of Gram-positive bacteria

A 28 kDa protein from normal mouse serum known to bind to the inner core region of bacterial lipopolysaccharide (LPS) was found to bind also to bacterial poly(glycerophosphate) lipoteichoic acid (LTA). Twenty-nine preparations of LTA were isolated from 19 different bacterial species, purified, chemically analysed, and tested for their ability to bind the 28 kDa protein in a complement-dependent hemolysis and hemolysis inhibition assay. All but one were active in one or both systems and one half of the preparations were active in both. Reactivity patterns were not strictly correlated with the chemical structure of LTA considering the substitution of the poly(glycerophosphate) chain with alanine ester and glycosyl residues and the type of lipid anchor. The isolated lipid anchor alone was unable to bind the serum factor. Comparing the binding to LTA and LPS from Acinetobacter calcoaceticus indicated complete cross-reactivity of LTA and LPS in various serological approaches. Thus, LPS and LTA which are unique amphiphiles in Gram-negative and Gram-positive bacteria, respectively, share a similar function in terms of binding the 28 kDa mouse serum protein.

Distribution analyses of chain substituents of lipoteichoic acids by chemical degradation

The lipoteichoic acid from Lactococcus lactis Kiel 48337 was analyzed. It had 61% of its glycerophosphate residues substituted with alpha-D-galactopyranosyl residues. Non-substituted glycerophosphate residues were split off by two alkaline hydrolyses and an intermediate enzymatic phosphomonoester cleavage. The resulting (GalGroP)nGroGal and (GalGroP)nGlc2Gro oligomers were separated by chromatography on DEAE-Sephadex into 10 pairs of molecular species with n from 1 to 10. The relative frequencies of GalGro and these oligomers were close to the values calculated by computer simulation for a random distribution of chain substituents. A similar series of oligomers was obtained in one step by hydrolysis of the lipoteichoic acid with 98% (by vol.) acetic acid. Due to side reactions, the picture was less precise but nevertheless indicative of the same distribution pattern. The data provide indirect evidence that the alanine ester substituents of the native lipoteichoic acid (Ala/P = 0.38) occupy the free positions between the galactosylated oligomers and are therefore themselves distributed randomly.

Optical resolution of amino acid derivatives by high-performance liquid chromatography on tris(phenylcarbamate)s of cellulose and amylose

The optical resolution of ten N-protected alanine esters was examined by high-performance liquid chromatography using six cellulose and five amylose tris(phenylcarbamate) derivatives as chiral stationary phases. Tris(3,5-dimethylphenylcarbamate)s of both cellulose and amylose showed high resolving power for these racemates. The resolution of 23 N-benzyloxycarbonyl α-amino acid esters was also tested on tris(3,5-dimethylphenylcarbamate)s of cellulose and amylose. All amino acid derivatives except two were completely resolved at least by one of the colums. On cellulose tris(3,5-dimethylphenylcarbamate), thel-isomers of the amino acids except for threonine were eluted first.

A simple spectrophotometric assay for urinary leukocyte esterase activity.

We have developed a sensitive spectrophotometric method for assaying urinary leukocyte esterase activity by employing a synthetic substrate, N-toluene sulfonyl indoxyl alanine ester. This kinetic assay can be performed with a small aliquot of urine, by following the change in absorbance of the chromophore at 385 nm. It is rapid and specific for leukocyte esterase and therefore can be used in the early diagnosis of urinary tract infection.

ChemInform Abstract: Alkylation of Imidazolidinone Dipeptide Derivatives: Preparation of Enantiomerically Pure Di‐ and Tripeptides by “Chirality Transfer” via a Pivalaldehyde N,N‐Acetal Center.

AbstractGlycylglycine, (S)‐alanylglycine and glycyl‐(S)‐alanine esters are cyclized through the pivaldehyde imines (I), (IVa), and (IVb) to give the dipeptide‐derived imidazolidinones (III), (Va), and (VIb).

Purification and characterization of aqualysin I (a thermophilic alkaline serine protease) produced by Thermus aquaticus YT-1.

Aqualysin I is an alkaline serine protease which is secreted into the culture medium by Thermus aquaticus YT-1. Aqualysin I was purified, and its apparent relative molecular mass was determined to be 28 500. The enzyme contained four Cys residues (probably as two cystines), and its amino acids composition was similar to those of cysteine-containing serine proteases (proteinase K, etc.) as well as those of subtilisins. The NH2-terminal sequence of aqualysin I showed homology with those of the microbial serine proteases. The optimum pH for the proteolytic activity of aqualysin I was around 10.0. Ca2+ stabilized the enzyme to heat treatment, and the maximum proteolytic activity was observed at 80 degrees C. Aqualysin I was stable to denaturing reagents (7 M urea, 6 M guanidine.HCl and 1% SDS) at 23 degrees C for 24 h. The enzyme hydrolyzed the ester bond of an alanine ester and succinyl-Ala-Ala-Ala p-nitroanilide, a synthetic substrate for mammalian elastase. The cleavage sites for aqualysin I in oxidized insulin B chain were not specific when it was digested completely.