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5 article(s) from Urabe, Daisuke

Nomimicins B–D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura

Zhiwei Zhang,
Tao Zhou,
Taehui Yang,
Keisuke Fukaya,
Enjuro Harunari,
Shun Saito,
Katsuhisa Yamada,
Chiaki Imada,
Daisuke Urabe and
Yasuhiro Igarashi

Full Research Paper
Published 27 Aug 2021

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1. Graphical Abstract
2. Figure 1: Structures of nomimicins A–D (4 and 1–3).
  
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3. Figure 2: COSY and key HMBC correlations for 1.
  
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4. Figure 3: Relative configuration of 1 determined by ROESY analysis.
  
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5. Figure 4: Experimental ECD spectra of 1, 2, and 4 and calculated ECD spectrum of 4.
  
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6. Figure 5: Four tautomers 4a–4d of the tetronic acid moiety of 4 and calculated ECD spectra.
  
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7. Figure 6: COSY and key HMBC correlations for 3.
  
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8. Figure 7: Relative configuration of 3 determined by NOESY analysis.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2021, 17, 2194–2202, doi:10.3762/bjoc.17.141

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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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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 new aromatic polyketides from a sponge-derived Fusarium

Mada Triandala Sibero,
Tao Zhou,
Keisuke Fukaya,
Daisuke Urabe,
Ocky K. Karna Radjasa,
Agus Sabdono,
Agus Trianto and
Yasuhiro Igarashi

Full Research Paper
Published 09 Dec 2019

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1. Graphical Abstract
2. Figure 1: Structures of compounds 1–7.
  
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3. Figure 2: Key HMBC correlations and two possible structures (a and b) for karimunone A (1).
  
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4. Figure 3: Key HMBC correlations for karimunone B (2).
  
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Beilstein J. Org. Chem. 2019, 15, 2941–2947, doi:10.3762/bjoc.15.289

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Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

Toshiki Tabuchi,
Daisuke Urabe and
Masayuki Inoue

Full Research Paper
Published 04 Apr 2013

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1. Graphical Abstract
2. Scheme 1: Structure of ryanodine and the Diels–Alder reactions for construction of the potential intermediate...
  
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3. Scheme 2: Asymmetric synthesis of 7 and determination of the absolute configuration at C4 of 15 by the modifi...
  
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4. Scheme 3: Generation of 17 through the 6π-electrocyclic reaction and the Diels–Alder reaction.
  
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5. Scheme 4: Rationale of the stereoselectivity of the Diels–Alder reaction.
  
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6. Scheme 5: Synthesis of C₂-symmetric 1.
  
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Graphical Abstract

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

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