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9 article(s) from Oku, Naoya

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

Yasuhiro Igarashi,
Yiwei Ge,
Tao Zhou,
Amit Raj Sharma,
Enjuro Harunari,
Naoya Oku and
Agus Trianto

Full Research Paper
Published 13 Jan 2022

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1. Graphical Abstract
2. Figure 1: Structures of tenacibactins K–M (1–3).
  
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3. Figure 2: Key 2D-NMR correlations for 1–3.
  
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4. Figure 3: (a) Partial ¹H NMR spectra of 1 at 25 and 50 °C in DMSO-d₆; (b) magnified HMBC spectrum of 1 at 25 ...
  
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5. Figure 4: MS/MS spectrum of 1 acquired on a quadrupole time-of-flight mass spectrometer in the negative ion m...
  
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6. Scheme 1: MS/MS fragmentation pathway for compound 1.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

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Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

Shun Saito,
Kanji Indo,
Naoya Oku,
Hisayuki Komaki,
Masashi Kawasaki and
Yasuhiro Igarashi

Full Research Paper
Published 16 Dec 2021

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1. Graphical Abstract
2. Figure 1: Structures of 1–6.
  
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3. Figure 2: COSY, key HMBC and NOESY correlations of 1–5.
  
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4. Figure 3: ¹H NMR spectra and partial chemical shift assignments for MPA esters 4'a–4'd. Upper: (R)-MPA acylat...
  
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5. Figure 4: Chiral phase HPLC analysis of methyl ester 4'. Italicized numbers indicate peak areas.
  
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6. Figure 5: COSY and key HMBC correlations observed for 6.
  
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7. Figure 6: Δδ_H(S-R) values in ppm calculated from PGME amides 6a and 6b.
  
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8. Figure 7: Selected examples of the related compounds derived from the strains in the genus Streptomyces (a) a...
  
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Graphical Abstract

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

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Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

Md. Rokon Ul Karim,
Enjuro Harunari,
Amit Raj Sharma,
Naoya Oku,
Kazuaki Akasaka,
Daisuke Urabe,
Mada Triandala Sibero and
Yasuhiro Igarashi

Full Research Paper
Published 05 Nov 2020

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1. Graphical Abstract
2. Figure 1: Structure of the nocarimidazoles 1–4 and the bulbimidazoles 5–7.
  
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3. Figure 2: COSY and key HMBC correlations for 1 and 2.
  
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4. Scheme 1: Synthesis of the model compounds 8 and 9.
  
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5. Figure 3: ¹J_C,H coupling constant for the imidazole ring of the natural products 1 and 5 and the model compou...
  
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6. Figure 4: Determination of the absolute configuration of 1 (a), 4 (b), and 5 (c) by the Ohrui–Akasaka method.
  
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7. Figure 5: Stereochemical diversity of the anteiso-chain chirality in microbial metabolites.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

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Three new O-isocrotonyl-3-hydroxybutyric acid congeners produced by a sea anemone-derived marine bacterium of the genus Vibrio

Dandan Li,
Enjuro Harunari,
Tao Zhou,
Naoya Oku and
Yasuhiro Igarashi

Full Research Paper
Published 29 Jul 2020

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1. Graphical Abstract
2. Figure 1: Structures of the compounds 1–5.
  
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3. Figure 2: COSY (bold lines) and selected HMBC correlations (arrows) for 1–4.
  
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4. Figure 3: a) Distribution of positive (red) and negative (blue) Δδ₍_S₋_R₎ values (in ppm) calculated from the ...
  
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Graphical Abstract

Beilstein J. Org. Chem. 2020, 16, 1869–1874, doi:10.3762/bjoc.16.154

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4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

Dandan Li,
Naoya Oku,
Yukiko Shinozaki,
Yoichi Kurokawa and
Yasuhiro Igarashi

Letter
Published 26 Jun 2020

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1. Graphical Abstract
2. Figure 1: Structures of compounds 1–5.
  
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3. Figure 2: COSY-deduced spin-system (bold lines) and key HMBC correlations (arrows) for compound 1, and struct...
  
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4. Figure 3: Extinction of luminol chemiluminescence by 1.
  
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Beilstein J. Org. Chem. 2020, 16, 1489–1494, doi:10.3762/bjoc.16.124

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A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

Shun Saito,
Kota Atsumi,
Tao Zhou,
Keisuke Fukaya,
Daisuke Urabe,
Naoya Oku,
Md. Rokon Ul Karim,
Hisayuki Komaki and
Yasuhiro Igarashi

Full Research Paper
Published 25 May 2020

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1. Graphical Abstract
2. Figure 1: Structures of pseudosporamide (1) and pseudosporamicins A–C (2–4).
  
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3. Figure 2: COSY, key HMBC and ROESY correlations of pseudosporamide (1).
  
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4. Figure 3: ¹H NMR Δδ_S−R values for PGME amides 5a and 5b obtained from compound 1.
  
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5. Figure 4: The opposite axial chirality around the biaryl C-6–C-7'' bond influenced by the C-2 configuration i...
  
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6. Figure 5: The experimental and calculated ECD spectra in MeCN.
  
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7. Figure 6: COSY, key HMBC and NOESY correlations of compound 2.
  
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8. Figure 7: NOESY correlations for the spiroacetal moiety of compound 2.
  
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9. Figure 8: Selected examples of oligomycin-class metabolites from actinomycetes.
  
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Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

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Two antibacterial and PPARα/γ-agonistic unsaturated keto fatty acids from a coral-associated actinomycete of the genus Micrococcus

Amit Raj Sharma,
Enjuro Harunari,
Naoya Oku,
Nobuyasu Matsuura,
Agus Trianto and
Yasuhiro Igarashi

Full Research Paper
Published 02 Mar 2020

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1. Graphical Abstract
2. Figure 1: Structures of (6E,8Z)- and (6E,8E)-5-oxo-6,8-tetradecadienoic acids (1 and 2).
  
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3. Figure 2: COSY and key HMBC correlations for 1 and 2.
  
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4. Figure 3: Spin system simulation for the C8–C9 double bond of 2.
  
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5. Figure 4: Natural keto fatty acids of various origins.
  
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6. Figure 5: PPAR activation by 1 and 2.
  
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Beilstein J. Org. Chem. 2020, 16, 297–304, doi:10.3762/bjoc.16.29

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Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

Dandan Li,
Naoya Oku,
Atsumi Hasada,
Masafumi Shimizu and
Yasuhiro Igarashi

Letter
Published 14 Jun 2018

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1. Graphical Abstract
2. Figure 1: Structures of compounds 1–8.
  
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3. Figure 2: Key COSY (bold line) and HMBC (arrow) correlations for 3.
  
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4. Figure 3: Referential ¹³C chemical shifts of an allylic carbon in burkholone [14] and haplacutine F [15].
  
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Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

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Sacrolide A, a new antimicrobial and cytotoxic oxylipin macrolide from the edible cyanobacterium Aphanothece sacrum

Naoya Oku,
Miyako Matsumoto,
Kohsuke Yonejima,
Keijiroh Tansei and
Yasuhiro Igarashi

Full Research Paper
Published 07 Aug 2014

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1. Graphical Abstract
2. Figure 1: Structure of sacrolide A (1).
  
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3. Figure 2: Selected COSY (bold lines) and HMBC (arrows) correlations for sacrolide A (1).
  
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4. Scheme 1: Initial derivatization strategy for the stereochemical analysis of sacrolide A (1).
  
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5. Scheme 2: Determination of the stereochemistry of sacrolide A (1).
  
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6. Scheme 3: Plausible biosynthesis of sacrolide A (1).
  
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7. Figure 3: The effect of sacrolide A (1) on 3Y1 rat fibroblastic cells. (a) Control. (b) 45 min after exposure...
  
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8. Figure 4: Extracted ion chromatograms for sacrolide A (1) molecular ion at m/z 307 [M – H]⁻ in the LC–MS anal...
  
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Beilstein J. Org. Chem. 2014, 10, 1808–1816, doi:10.3762/bjoc.10.190

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