NMR-based assignment of isoleucine<i>vs</i>.<i>allo</i>-isoleucine stereochemistry

Anderson, Zoe; Hobson, Christian; Needley, Rebecca; Song, Lijiang; Perryman, Michael S.; Kerby, Paul D.; Fox, David J.

doi:10.1039/c7ob01995e

Cited by 8 publications

(10 citation statements)

References 73 publications

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“…The strong NOESY correlations between H-2’ (δ H 3.48)/H-3’ (δ H 1.80) and H-2’ (δ H 3.48)/CH 3 -6’ (δ H 0.83) indicated that the relative configuration of the 2-substituted-3-methylpentanoic acid subunit of compound 1 was as shown in Fig 2 (Fig A.12 in S1 File ). This was further supported by the comparison of spin-spin coupling constants between protons H-2’ and H-3’ ( 3 J CH-CH 5.1 Hz) and chemical shift values of the H-2’ and H-3’ protons with the similar structural fragments of 2-amino-3-methylpentanoic acid subunits ( Fig 2 ) (Fig A.12 in S1 File ) [ 18 , 19 ]. Similarly, relative stereochemistry of the 2-substituted-4-methylpentanoic acid subunit of compound 1 was assigned by the analysis of NOESY correlations between H-2’’ (δ H 3.55)/H-3’’ (δ H 1.55) and H-2’’ (δ H 3.55)/CH 3 -5’’ and 6’’ (δ H 0.79) as shown in Fig 2 (Fig A.12 in S1 File ).…”

Section: Resultsmentioning

confidence: 83%

“…Connectivity of the 2-substituted-4-methylpentanoic acid subunit to the uracil ring was deduced by the HMBC correlations of H-3 (δ H 7.35) to C-2’’ (δ C 59.4) ( Fig 2 ) (Fig A.11 in S1 File ). The relative configuration of compound 1 was determined by the analysis of the NOESY experiment and spin-spin coupling constants (Fig A.12 in S1 File ) ( Table 1 ) [ 18 , 19 ]. The strong NOESY correlations between H-2’ (δ H 3.48)/H-3’ (δ H 1.80) and H-2’ (δ H 3.48)/CH 3 -6’ (δ H 0.83) indicated that the relative configuration of the 2-substituted-3-methylpentanoic acid subunit of compound 1 was as shown in Fig 2 (Fig A.12 in S1 File ).…”

Section: Resultsmentioning

confidence: 99%

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Evaluation of health benefits of sea lamprey (Petromyzon marinus) isolates using in vitro antiinflammatory and antioxidant assays

2021

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Sea lamprey (Petromyzon marinus), a parasitic fish which survives on blood of other fishes, is consumed as a delicacy in many countries. Our earlier studies on sea lamprey compounds that showed potential to deter adult sea lampreys yielded several sterols, glycerides, free fatty acids, amino acids, organic acids and nitrogenous compounds. Therefore, this study was to assess the health-benefits of these compounds including additional isolates from HPLC fractions that kept aside due to lack of activity in sea lamprey deterrent assays. In vitro cyclooxygenase enzymes (COX-1 and -2) and lipid peroxidation (LPO) inhibitory assays, respectively, were used to determine antiinflammatory and antioxidant activities. Among the tested sterols, cholesteryl eicosapentaenoate and cholesteryl arachidonate exhibited IC50 values of 14.6 and 17.7 μg/mL for COX-1 and 17.3 and 20.8 μg/mL for COX-2, respectively. Cholesteryl palmitate and cholesteryl oleate showed moderate COX-1 and COX-2 enzyme inhibition at 25 μg/mL. Amino acids arginine, tyrosine, glutamic acid, tryptophan and asparagine also showed moderate COX-1 and COX-2 inhibition at the same concentration. Among the twelve new isolates from fractions that we did not investigate earlier, a novel uracil derivative petromyzonacil showed COX-1 and COX-2 inhibition at 25 μg/mL by 35 and 15%, respectively. Cholesterol esters tested at 25 μg/mL exhibited LPO inhibition between 38 and 82 percent. Amino acids cysteine, methionine, aspartic acid, threonine, tryptophan, histidine, glutamic acid, phenylalanine and tyrosine at 25 μg/mL showed LPO inhibition between 37 and 58% and petromyzonacil by 32%. These assay results indicate that consumption of sea lamprey offer health-benefits in addition to nutritional benefits.

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Section: Resultsmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Evaluation of health benefits of sea lamprey (Petromyzon marinus) isolates using in vitro antiinflammatory and antioxidant assays

2021

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“…When enantiopure amino acids were employed as N -nucleophiles in our methodology, no degradation of the stereochemical integrity was observed, indicating that no epimerization of 6d – 6f had occurred during the process. 20 , 21 The addition of amino acids as a solution in water was also tolerated under the reaction conditions, further demonstrating the robustness of this protocol.…”

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confidence: 80%

Amide Bond Formation via the Rearrangement of Nitrile Imines Derived from N-2-Nitrophenyl Hydrazonyl Bromides

et al. 2021

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We report how the rearrangement of highly reactive nitrile imines derived from N -2-nitrophenyl hydrazonyl bromides can be harnessed for the facile construction of amide bonds. This amidation reaction was found to be widely applicable to the synthesis of primary, secondary, and tertiary amides and was used as the key step in the synthesis of the lipid-lowering agent bezafibrate. The orthogonality and functional group tolerance of this approach was exemplified by the N -acylation of unprotected amino acids.

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“…The lack of any NOESY correlation between H-4 and H-6 suggested the opposite (β) orientation of H-4. The relative configuration of C-10 was assigned by comparison of the 1 H and13 C NMR data of 8 with those of structurally similar compounds containing the isoleucine group[25,26]. A literature survey indicated that 8 shares identical NMR data with the known DKP, cyclo(D-trans-Hyp-D-Ile) isolated from the marine sponge Stelletta sp [27],.…”

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confidence: 99%

Integrating Molecular Networking and 1H NMR Spectroscopy for Isolation of Bioactive Metabolites from the Persian Gulf Sponge Axinella sinoxea

Kouchaksaraee

Farimani

et al. 2020

Marine Drugs

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The geographic position, highly fluctuating sea temperatures and hypersalinity make Persian Gulf an extreme environment. Although this unique environment has high biodiversity dominated by invertebrates, its potential in marine biodiscovery has largely remained untapped. Herein, we aimed at a detailed analysis of the metabolome and bioactivity profiles of the marine sponge Axinella sinoxea collected from the northeast coast of the Persian Gulf in Iran. The crude extract and its Kupchan subextracts were tested in multiple in-house bioassays, and the crude extract and its CHCl3-soluble portion showed in vitro antibacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA) and Enterococcus faecium (Efm). A molecular networking (MN)-based dereplication strategy by UPLC-MS/MS revealed the presence of phospholipids and steroids, while 1H NMR spectroscopy indicated the presence of additional metabolites, such as diketopiperazines (DKPs). Integrated MN and 1H NMR analyses on both the crude and CHCl3 extracts combined with an antibacterial activity-guided isolation approach afforded eight metabolites: a new diketopiperazine, (-)-cyclo(L-trans-Hyp-L-Ile) (8); a known diketopiperazine, cyclo(L-trans-Hyp-L-Phe) (7); two known phospholipids, 1-O-hexadecyl-sn-glycero-3-phosphocholine (1) and 1-O-octadecanoyl-sn-glycero-3-phosphocholine (2); two known steroids, 3β-hydroxycholest-5-ene-7,24-dione (3) and (22E)-3β-hydroxycholesta-5,22-diene-7,24-dione (4); two known monoterpenes, loliolide (5) and 5-epi-loliolide (6). The chemical structures of the isolates were elucidated by a combination of NMR spectroscopy, HRMS and [α]D analyses. All compounds were tested against MRSA and Efm, and compound 3 showed moderate antibacterial activity against MRSA (IC50 value 70 μg/mL). This is the first study that has dealt with chemical and bioactivity profiling of A. sinoxea leading to isolation and characterization of pure sponge metabolites.

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NMR-based assignment of isoleucinevs.allo-isoleucine stereochemistry

Cited by 8 publications

References 73 publications

Evaluation of health benefits of sea lamprey (Petromyzon marinus) isolates using in vitro antiinflammatory and antioxidant assays

Evaluation of health benefits of sea lamprey (Petromyzon marinus) isolates using in vitro antiinflammatory and antioxidant assays

Amide Bond Formation via the Rearrangement of Nitrile Imines Derived from N-2-Nitrophenyl Hydrazonyl Bromides

Integrating Molecular Networking and 1H NMR Spectroscopy for Isolation of Bioactive Metabolites from the Persian Gulf Sponge Axinella sinoxea

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