62 research outputs found

    Optional Synthesis of 2- or 5-Substituted 3-Bromopyrroles via Bromine-Lithium Exchange of N-Benzenesulfonyl-2,4-dibromopyrrole

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    The regioselective bromine–lithium exchange of N-benzenesulfonyl-2,4-dibromopyrrole (6) with n-BuLi followed by treatment with various electrophiles gave 5-substituted 3-bromopyrroles (5) in excellent yields. In contrast, the sequential treatment of 6 with n-BuLi and diisopropylamine followed by quenching with electrophiles produced regioisomeric 2-substituted 3-bromopyrroles (3) selectively. The latter reaction can be rationalized by the rapid equilibration of the C-5 lithio species (4) to the more stable C-2 lithio species (2) in the presence of diisopropylamine

    A GENERAL METHOD FOR THE SYNTHESIS OF N-UNSUBSTITUTED 3,4-DIARYLPYRROLE-2,5-DICARBOXYLATES

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    A general method for the synthesis of N-unsubstituted 3,4-diarylpyrrole-2,5-dicarboxylates (3) has been developed. The key reactions involved are the Hinsberg-type synthesis of dimethyl N-benzyl-3,4-dihydroxypyrrole-2,5-dicarboxylate (6) followed by palladium-catalyzed Suzuki-Miyaura coupling of its bis-triflate derivative (7). The N-benzyl protecting group of the resulting 3,4-diarylpyrrole-2,5-dicarboxylates (8) is cleanly removed under hydrogenolytic or solvolytic conditions

    Design and Synthesis of Novel Lamellarin D Analogues Targeting Topoisomerase I

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    ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lectur

    Synthesis of Non-Steroidal Estrogen Receptor Antagonists R1128 A, B, C, and D via an Oxazoline-Promoted Iterative ortho-Lithiation Strategy

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    A concise total synthesis of non-steroidal estrogen receptor antagonists R1128 A–D (1a–1d) has been achieved using iterative ortho-lithiation of 2-(4-methoxyphenyl)-4,4-dimethyloxazoline (3) as the key reaction

    Efficient Total Syntheses of Heterocyclic Marine Alkaloids, Lamellarins

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    Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio

    Palladium-catalyzed cross-coupling of N-benzenesulfonyl-3,4-dibromopyrrole and its application to the total syntheses of lamellarins O, P, Q, and R

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    Palladium-catalyzed Suzuki--Miyaura coupling of N-benzenesulfonyl-3,4-dibromopyrrole with a variety of arylboronic acids gave the corresponding 3,4-diarylpyrroles in high yields. The 3,4-differentially arylated pyrroles could also be prepared by stepwise cross-coupling approach. The total syntheses of lamellarins O, P, Q, and R have been achieved by using the cross-coupling and the directed lithiation as key reactions

    A formal total synthesis of the telomerase inhibitor dictyodendrin B

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    A formal synthesis of the telomerase inhibitory marine pyrrolocarbazole alkaloid dictyodendrin B is described. The key features are consecutive palladium-catalyzed cross-coupling reactions and intramolecular reductive coupling reaction to construct the pyrrolo[2,3-c]carbazole framework

    Total synthesis of the marine natural products lukianols A and B

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    Total synthesis of the pyrrolic marine natural products lukianols A (1) and B (2) has been achieved using N-benzenesulfonyl-3,4-dibromopyrrole (3) as a common starting material. The key synthetic strategy developed is the combined bromine-directed lithiation and palladium-catalyzed cross-coupling of 3 to produce 3,4-diarylpyrrol-2-carboxylates. Regioselective iodination of the phenolic intermediate 24 was thoroughly investigated for the synthesis of lukianol B

    Unique Mode of Antiviral Action of a Marine Alkaloid against Ebola Virus and SARS-CoV-2

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    Lamellarin α20-sulfate is a cell-impenetrable marine alkaloid that can suppress infection that is mediated by the envelope glycoprotein of human immunodeficiency virus type 1. We explored the antiviral action and mechanisms of this alkaloid against emerging enveloped RNA viruses that use endocytosis for infection. The alkaloid inhibited the infection of retroviral vectors that had been pseudotyped with the envelope glycoprotein of Ebola virus and SARS-CoV-2. The antiviral effects of lamellarin were independent of the retrovirus Gag-Pol proteins. Interestingly, although heparin and dextran sulfate suppressed the cell attachment of vector particles, lamellarin did not. In silico structural analyses of the trimeric glycoprotein of the Ebola virus disclosed that the principal lamellarin-binding site is confined to a previously unappreciated cavity near the NPC1-binding site and fusion loop, whereas those for heparin and dextran sulfate were dispersed across the attachment and fusion subunits of the glycoproteins. Notably, lamellarin binding to this cavity was augmented under conditions where the pH was 5.0. These results suggest that the final action of the alkaloid against Ebola virus is specific to events following endocytosis, possibly during conformational glycoprotein changes in the acidic environment of endosomes. Our findings highlight the unique biological and physicochemical features of lamellarin α20-sulfate and should lead to the further use of broadly reactive antivirals to explore the structural mechanisms of virus replication

    Unique Mode of Antiviral Action of a Marine Alkaloid against Ebola Virus and SARS-CoV-2.

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    Lamellarin α 20-sulfate is a cell-impenetrable marine alkaloid that can suppress infection that is mediated by the envelope glycoprotein of human immunodeficiency virus type 1. We explored the antiviral action and mechanisms of this alkaloid against emerging enveloped RNA viruses that use endocytosis for infection. The alkaloid inhibited the infection of retroviral vectors that had been pseudotyped with the envelope glycoprotein of Ebola virus and SARS-CoV-2. The antiviral effects of lamellarin were independent of the retrovirus Gag-Pol proteins. Interestingly, although heparin and dextran sulfate suppressed the cell attachment of vector particles, lamellarin did not. In silico structural analyses of the trimeric glycoprotein of the Ebola virus disclosed that the principal lamellarin-binding site is confined to a previously unappreciated cavity near the NPC1-binding site and fusion loop, whereas those for heparin and dextran sulfate were dispersed across the attachment and fusion subunits of the glycoproteins. Notably, lamellarin binding to this cavity was augmented under conditions where the pH was 5.0. These results suggest that the final action of the alkaloid against Ebola virus is specific to events following endocytosis, possibly during conformational glycoprotein changes in the acidic environment of endosomes. Our findings highlight the unique biological and physicochemical features of lamellarin α 20-sulfate and should lead to the further use of broadly reactive antivirals to explore the structural mechanisms of virus replication
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