Absolute Configurations Of Amino Acids Research Articles

Neopetromin, a Cyclic Tripeptide with a C-N Cross-Link, from the Marine Sponge Neopetrosia sp., That Causes Vacuole Fragmentation in Tobacco BY-2 Cells.

HPLC-MS analysis revealed the presence of an unreported peptide in the extract of the marine sponge Neopetrosia sp. Its structure was determined as a tripeptide, named neopetromin (1), composed of two tyrosine and one tryptophan residues with a heteroaromatic C-N cross-link between side chains. The absolute configuration of amino acids was determined using Marfey's method after ozonolysis and hydrolysis of 1. Compound 1 promoted vacuole fragmentation in an actin-independent manner in tobacco BY-2 cells.

19F NMR enantiodiscrimination and diastereomeric purity determination of amino acids, dipeptides, and amines.

Chiral amino-group compounds are of significance for human health, such as biogenic amino acids (AAs), dipeptides, and even various drugs. Enantiospecific discrimination of these chiral compounds is vital in diagnosing diseases, identifying pathological biomarkers and enhancing pharmaceutical chemistry research. Here, we report a simple and rapid 19F NMR-based strategy to differentiate chiral AAs, dipeptides, and amines, that were derivatized with (R)-2-(2-fluorophenyl)-2-hydroxyacetic acid ((R)-2FHA). As a result, 19 proteinogenic AAs (37 isomers) as well as Gly could be concurrently resolved. Moreover, various mirror-image dipeptides, such as Ser-His, Leu-Leu, and Ala-Ala, were commendably recognized. Intriguingly, we found that the absolute configuration of AAs in the N-terminus of dipeptides decided the relative 19F chemical shifts between two enantiomers. Besides, the ability of this method for enantiodiscrimination was further demonstrated by non-AA amines, including aromatic and aliphatic amines, and even amines having chiral centers several carbons away from the amino-group. The structurally similar antibiotics, amoxicillin and ampicillin, were well discriminated. Furthermore, this method accurately determines the de or dr values of non-racemic mixtures. Therefore, our strategy provides an effective approach for 19F NMR-based enantiodiscrimination and diastereomeric purity determination of amino-group compounds.

Chiral molecular nanosilicas.

Molecular nanoparticles including polyoxometalates, proteins, fullerenes and polyhedral oligosiloxane (POSS) are nanosized objects with atomic precision, among which POSS derivatives are the smallest nanosilicas. Incorporation of molecular nanoparticles into chiral aggregates either by chiral matrices or self-assembly allows for the transfer of supramolecular chirality, yet the construction of intrinsic chirality with atomic precision in discrete molecules remains a great challenge. In this work, we present a molecular folding strategy to construct giant POSS molecules with inherent chirality. Ferrocenyl diamino acids are conjugated by two or four POSS segments. Hydrogen bonding-driven folding of diamino acid arms into parallel β-sheets facilitates the chirality transfer from amino acids to ferrocene and POSS respectively, disregarding the flexible alkyl spacers. Single crystal X-ray structures, density functional theory (DFT) calculations, circular dichroism and vibrational circular dichroism spectroscopy clearly verify the preferential formation of one enantiomer containing chiral molecular nanosilicas. The chiral orientation and chiroptical properties of POSS show pronounced dependence on the substituents of α-amino acids, affording an alternative way to control the folding behavior and POSS chirality in addition to the absolute configuration of amino acids. Through the kinetic nanoprecipitation protocol, one-dimensional aggregation enables chirality transfer from the molecular scale to the micrometer scale, self-assembling into helices in accordance with the packing propensity of POSS in a crystal phase. This work, by illustrating the construction of chiral molecular nanosilicas, paves a new way to obtain discrete chiral molecular nanoparticles for potential chiroptical applications.

Cyclopeptide Derivatives from the Sponge-Derived Fungus Acremonium persicinum F10.

Cyclopeptides usually play a pivotal role, either in the viability or virulence of fungi. Two types of cyclopeptides, six new hydroxamate siderophore cyclohexapeptides (1–6), including acremonpeptides E and F, and their complexes with aluminum and ferric ions; one new cyclic pentapeptolide, aselacin D (9); together with a known compound, aselacin C (10), were isolated and characterized from the sponge-derived fungus Acremonium persicinum F10. In addition, two new siderophore analogues chelating gallium ions (Ga3+), Ga (III)-acremonpeptide E (7) and Ga (III)-acremonpeptide F (8), using isolated acremonpeptides E and F, were prepared. The planar structures of 1–10 were elucidated by HRESIMS and (1D and 2D) NMR. The absolute configurations of amino acids were determined by means of the advanced Marfey’s method and X-ray single-crystal diffraction analysis. X-ray fluorescence (XRF) spectrometer was performed to disclose the elements of compound 1, indicating the existence of aluminum (Al). Al (III)-acremonpeptides E (1), Ga (III)-acremonpeptides E (5), Al (III)-acremonpeptide F (7), and Ga (III)-acremonpeptide F (8) displayed high in vitro anti-fungal activities, which are comparable to amphotericin B, against Aspergillus fumigatus and Aspergillus niger.

Phototemtide A, a Cyclic Lipopeptide Heterologously Expressed from Photorhabdus temperata Meg1, Shows Selective Antiprotozoal Activity.

A new cyclic lipopeptide, phototemtide A (1), was isolated from Escherichia coli expressing the biosynthetic gene cluster pttABC from Photorhabdus temperata Meg1. The structure of 1 was elucidated by HR‐ESI‐MS and NMR experiments. The absolute configurations of amino acids and 3‐hydroxyoctanoic acid in 1 were determined by using the advanced Marfey's method and comparison after total synthesis of 1, respectively. Additionally, three new minor derivatives, phototemtides B–D (2–4), were identified by detailed HPLC–MS analysis. Phototemtide A (1) showed weak antiprotozoal activity against Plasmodium falciparum, with an IC50 value of 9.8 μm. The biosynthesis of phototemtides A–D (1–4) was also proposed.

The potential of intracellular 13C MR spectroscopy to study the absolute configuration of endogenous and polarized alanine

Introduction. Quantitative and accurate monitoring of tumor makes hyperpolarized carbon (13C) Magnetic Resonance Imaging and Spectroscopy (MRI/S) a powerful tool for in vivo metabolic and structural study. Moreover, the studies of the properties and functions in tumor tissue of the compounds of carbon (C) that are organic, are fundamental to tumor biochemistry. Aim. To review 13C MR spectroscopy to study the absolute configuration of endogenous and polarized alanine Material and methods. An analysis of literature regarding 13C MR spectroscopy of polarized alanine. Results. Current evidence suggests that the determination of absolute configurations of amino acids play significant role in physiological mechanisms during tumor growth and treatment. Conclusions. Nearly 50% nuclear polarization for 13C can be achieved in various organic molecules when Dynamic Nuclear Polarization DNP is performed in a strong magnetic field and at cryogenic temperatures.

Structure, Biosynthesis, and Bioactivity of Photoditritide from Photorhabdus temperata Meg1.

A new cyclic peptide photoditritide (1), containing two rare amino acid d-homoarginine residues, was isolated from Photorhabdus temperata Meg1 after the nonribosomal peptide synthetase encoding gene pdtS was activated via promoter exchange. The structure of 1 was elucidated by HR-MS and NMR experiments. The absolute configurations of amino acids were determined according to the advanced Marfey's method after hydrolysis of 1. Bioactivity testing of 1 revealed potent antimicrobial activity against Micrococcus luteus with an MIC value of 3.0 μM and weak antiprotozoal activity against Trypanosoma brucei rhodesiense with an IC50 value of 13 μM. Additionally, the biosynthetic pathway of 1 was also proposed.

Anti-MRSA actinomycins D1-D4 from the marine sponge-associated Streptomyces sp. LHW52447

Actinomycins D1−D4 (1–4), four new D-type actinomycin analogues, were isolated from the fermentation broth of a strain of marine sponge-associated Streptomyces sp. LHW52447, together with actinomycin D (5). The structures of 1−4 were determined by a combination analysis of HRMS and NMR spectroscopic methods, and their absolute configurations of amino acids were determined by Marfey's analysis. Actinomycins D1 (1) and D2 (2) are the first two naturally occurring actinomycins with incorporation an oxazole unit into the central phenoxazinone chromophore. Both 1 and 2 showed more potent antibacterial activities against three strains of pathogenic methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 0.125–0.25 μg/mL than those of 3−5 with MIC values of 0.5–1.0 μg/mL, which suggested that the anti-MRSA activity might be enhanced by the incorporation of an additional oxazole unit. In addition, the cytotoxicity evaluation against WI-38 human diploid lung fibroblasts revealed that the incorporation of oxazole unit could decrease the cytotoxicity of actinomycins on human normal cells.

Iminolactones as tools for inversion of the absolute configuration of α-amino acids and as inhibitors of cancer cell proliferation

A library of iminolactones was prepared by esterification of several 2-hydroxyketones with a number of N-protected d- and l-α-amino acids. Some of the hydroxyketones were of terpenoid origin while others were obtained via synthesis. After N-deprotection of the intermediate esters, the free amines spontaneously underwent condensation with the ketone to form iminolactones. Esters of (1S,2S,5S)-2-hydroxypinan-3-one with both d- and l-α-amino acids were partially epimerized at the α-carbon atom to give a diastereomeric ester mixture. Only iminolactones of l-amino acids were formed after cyclization of (1S,2S,5S)-2-hydroxypinan-3-one, and correspondingly only d-amino acid iminolactones were formed after reaction with (1R,2R,5R)-2-hydroxypinan-3-one. The protocol thus enables inversion of the absolute configuration of amino acids. Some members of the prepared library of iminolactones displayed significant anti-proliferative effects toward three cancer cell lines (EL4, MCF7, PC3) with insignificant effect on non-malign cell lines (McCoy, MCF10A, NIH3T3). Thus, iminolactones appear to be potential lead structures for preparation of drugs selectively affecting proliferation of malign cell lines.

Ohmyungsamycins A and B: Cytotoxic and Antimicrobial Cyclic Peptides Produced by Streptomyces sp. from a Volcanic Island

Ohmyungsamycins A and B (1 and 2), which are new cyclic peptides, were isolated from a marine bacterial strain belonging to the Streptomyces genus collected from a sand beach on Jeju, a volcanic island in the Republic of Korea. Based on the interpretation of the NMR, UV, and IR spectroscopic and MS data, the planar structures of 1 and 2 were elucidated as cyclic depsipeptides bearing unusual amino acid units, including N-methyl-4-methoxytrytophan, β-hydroxyphenylalanine, and N,N-dimethylvaline. The absolute configurations of the α-carbons of the amino acid residues were determined using the advanced Marfey's method. The configurations of the additional stereogenic centers at the β-carbons of the threonine, N-methylthreonine, and β-hydroxyphenylalanine units were assigned by GITC (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl isothiocyanate) derivatization and the modified Mosher's method. We have developed a new method utilizing PGME (phenylglycine methyl ester) derivatization coupled with chromatographic analysis to determine the absolute configuration of N,N-dimethylvaline. Our first successful establishment of the absolute configuration of N,N-dimethylvaline using PGME will provide a general and convenient analytical method for determining the absolute configurations of amino acids with fully substituted amine groups. Ohmyungsamycins A and B showed significant inhibitory activities against diverse cancer cells as well as antibacterial effects.

Pullularins E and F, Two New Peptides from the Endophytic Fungus Bionectria ochroleuca Isolated from the Mangrove Plant Sonneratia caseolaris

Chemical investigation of the EtOAc extract of the endophytic fungus Bionectria ochroleuca, isolated from the inner leaf tissues of the plant Sonneratia caseolaris (Sonneratiaceae) from Hainan island (China), yielded two new peptides, pullularins E and F (1 and 2) together with three known compounds (3–5). The structures of the new compounds were unambiguously determined on the basis of one- and two-dimensional NMR spectroscopy as well as by high-resolution mass spectrometry. The absolute configurations of amino acids were determined by HPLC analysis of acid hydrolysates using Marfey’s method. The isolated compounds exhibited pronounced to moderate cytotoxic activity against the mouse lymphoma cells (L5178Y) with EC50 values ranging between 0.1 and 6.7 µg/mL.

New C14-surfactin methyl ester from the marine bacterium Bacillus pumilus KMM 456

New C14-surfactin methyl ester and eight earlier described surfactins were isolated from the marine bacterium Bacillus pumilus associated with zoantharia Palythoa sp. The structure of the compounds isolated was established based on the data from amino acid analysis, one- and two-dimensional NMR spectroscopy, and tandem nanoelectrospray mass spectrometry. The absolute configurations of amino acids were determined by Marfey’s method. Cytotoxic activity of a number of surfactins with respect to the tumor cells HCT-116 and MDA-MB-231 was studied.

ChemInform Abstract: Elucidation of the Absolute Configurations of Amino Acids and Amines by the Modified Mosher′s Method.

Abstract Application of the modified Mosher's method to the N -MTPA derivatives of several amino acid esters and acyclic amines indicates that this method may be generally used to determine the absolute configurations of the α-carbons of amino compounds of less than 0.1 mg amount.

Elution behavior of diaminopimelic acid and related diamino acids using the advanced Marfey's method

The advanced Marfey's method consists of a chromatography technique for the separation of amino acids into each enantiomer by derivatization with 1-fluoro-2,4-dinitrophenyl-5- l-leucinamide ( l-FDLA), and a detection method using liquid chromatography/mass spectrometry (LC/MS) which can determine the non-empirically the absolute configuration of various amino acids including the non-protein ones. However, this method has not been applied to the determination of the absolute configuration of an amino acid with a “meso” configuration such as diaminopimelic acid (A 2pm). In the present study, this method was successfully applied to determine the absolute configurations of diaminosuccinic acid (DAS), A 2pm, cystine (Cys), selenocystine (SeCys) and homocystine (HomoCys) using a racemization procedure and the dl-FDLA method, and the resulting elution behavior was summarized as follows: (1) the ll- and meso-isomers were eluted prior to the dd-isomer except for one case; (2) the ll- and meso-isomers are closely eluted and the elution was occasionally reversed; (3) the retention time for both the l- and d-derivatives of the meso-isomer was not changed; (4) the complementary use of the two solvent systems using CH 3CN and MeOH was effective to obtain a chromatogram with a high resolution; (5) the abnormality, such as the elution order and peak shape, was observed in the elution behavior of DAS.

Determination of absolute configurations of amino acids by asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol as a chiral sensor

Asymmetric autocatalysis of 2-alkynyl-5-pyrimidyl alkanol is employed as a chiral sensor of 20 amino acids. Asymmetric autocatalysis using amino acids as chiral initiators gave pyrimidyl alkanols of the absolute configurations that were correlated with those of the amino acids. The enantiomeric excesses of pyrimidyl alkanol are invariably high even when the enantiomeric excess of amino acids is as low as 0.1%. Thus, by determining the absolute configuration of pyrimidyl alkanol with high enantiomeric excess, one can determine the absolute configuration of amino acids even when their enantiomeric excess is low.

Cyclic Heptapeptides from the Jamaican Sponge Stylissa caribica

Two new cyclic heptapeptides, stylisin 1(1) and stylisin 2 (2), were isolated and characterized from the Jamaican sponge Stylissa caribica, in addition to the cyclic heptapeptide phakellistatin 13 (3) and the known bromopyrrole alkaloids sceptrin (4), stevensine (5), and oroidin (6). The new structures were assigned on the basis of 1D and 2D NMR spectroscopic data, as well as chemical methods for the elucidation of the absolute configuration of amino acids. The peptides and alkaloids have been evaluated for their antimicrobial, antimalarial, anticancer, anti-HIV-1, anti-Mtb, and antiinflammatory activities.

Dimolybdenum Tetraacetate as an Auxiliary Chromophore in Absolute Configuration Determination of Amino Acids from their Circular Dichroism Spectra - Foundations and Developments

A straightforward and versatile method for the determination of the absolute configuration of amino acids is presented. The proposed method involves the in situ formation of chiral complexes of optically active amino acids with the achiral dimolybdenum tetraacetate (Mo2(OAc)4) acting as an auxiliary chromophore. Optically active amino acids in reaction with (Mo2(OAc)4) in DMSO exchange in situ its acetate ligand to form chiral Mo-complexes. These complexes display several CD bands in the spectral range from 600 to 250 nm. The resulting CD spectra are suitable for the assignment of absolute configuration, since the observed sign of Cotton effects arising within the d−d absorption bands of the metal core depends solely upon the chirality of the amino acid ligands. It is shown that two Cotton effects at around 300 nm and 400 nm are especially useful for the correlation between their sign and the stereostructure of amino acids by means of the hexadecant rule. The present study demonstrates that the hexadecant rule can be extended to differently N-protected amino acids. The dimolybdenum method can also be applied for determination of the absolute configuration of cyclic β-amino acids representing precursors of peptidomimetics.

P-26 アミノ酸およびペプチドの絶対配置決定に有用なキラルランタニドシフト試薬(ポスター発表の部)

P-26 アミノ酸およびペプチドの絶対配置決定に有用なキラルランタニドシフト試薬(ポスター発表の部)

Use of Induced Circularly Polarized Luminescence (CPL) from Racemic D3 Lanthanide Complexes to Determine the Absolute Configuration of Amino Acids

The perturbation of the racemic equilibrium of luminescent D(3) lanthanide(III) complexes by added chiral agents, such as amino acids, may be a useful technique for determining the absolute configuration of the added species. It is shown in this work, however, that simple interpretation of the equilibrium shift of racemic tris-terdentate complexes of Tb(III) with 2,6-pyridine-dicarboxylate by amino acids, as measured by the sign of the resultant circularly polarized luminescence (CPL) in terms of specific structural characteristics is not possible. CPL results for a number of derivatized amino acids are also presented, and some insights into the nature of the chiral discriminatory forces that might be exploited in this kind of study are discussed.

A Nonempirical Method Using LC/MS for Determination of the Absolute Configuration of Constituent Amino Acids in a Peptide: Elucidation of Limitations of Marfey's Method and of Its Separation Mechanism

As the first step in establishing our proposed method, the advanced Marfey's method, which is planned for the simultaneous determination of the absolute configuration of amino acids in a peptide, we applied Marfey's method to commercially available amino acids, and the separation behavior was examined in detail. Although good resolution of the diastereomeric pair of an individual amino acid was obtained for all amino acids tested and the applicability of the method was confirmed, the (1-fluoro-2,4-dinitrophenyl)-5-l-alaninamide (FDAA) derivative of the l-amino acid was not always eluted prior to its corresponding d-amino acid derivative. Because this proposed method relies on the elution order of a derivatized amino acid with FDAA to determine its absolute configuration, its separation mechanism was carefully investigated using UV and NMR spectral techniques. The results suggested that the resulting conformations of the l- and d-amino acid derivatives are stable and that the resolution between the l- and d-amino acid derivatives is due to the difference in their hydrophobicity, which is derived from the cis- or trans-type arrangement of two more hydrophobic substituents at both α-carbons of an amino acid and l-alanine amide, so that the FDAA derivative of the cis (Z)-type arrangement interacts more strongly with ODS silica gel and has a longer retention time than that of the trans (E)-type arrangement. Therefore, the l-amino acid derivative is usually eluted from the column before its corresponding d-amino acid derivative in Marfey's method. According to this separation mechanism, the elution order of a desired amino acid can be elucidated from the average retention time of the l- and d-amino acid derivatives, and the dl-serine and -asparagine derivatives are critical for Marfey's method.