- Lewis Acid-Catalyzed Stereoselective α-Addition of Chiral Aldehydes to Cyclic Dienol Silanes: Aqueous Synthesis of Chiral Butenolides
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The stereoselective α-addition to cyclic dienol silanes has rarely been exploited, in contrast to the well-studied γ-addition of conjugated butenolides. In this study, an unprecedent catalytic Mukaiyama aldol α-addition of 2-trimetylsiloxy furan to optically pure aldehydes in water-containing solvents is reported. The synthetic utility of this concept was demonstrated in the efficient synthesis of six bioactive natural products: vitexolide D, curcucomosin C, villosin, chinensine C, (+)-coronarin E and (E)-labda-7,11,13-trien-16,15-olid.
- Adamkiewicz, Anna,W?glarz, Izabela,Butkiewicz, Aleksandra,Woyciechowska, Marta,Mlynarski, Jacek
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p. 667 - 678
(2019/12/24)
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- The identification of naturally occurring labdane diterpenoid calcaratarin D as a potential anti-inflammatory agent
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In this study we report, for the first time, the synthesis of the natural product calcaratarin D via a stereo- and regio-selective aldol condensation with (S)-β-hydroxy-γ-butyrolactone as key steps. A concise synthetic route (under 10 steps) to a series of structurally related normal-labdane diterpenes was also developed and their anti-inflammatory activities were evaluated in an in vitro model of inflammation. The structure-activity relationships (SARs) pertaining to the labdane scaffold were elucidated and results suggest that an α-alkylidene-β-hydroxy-γ-butyrolactone system is necessary for potent activity in the labdanes. Our studies identified the natural product calcaratarin D (1) as a promising anti-inflammatory agent, which effectively modulates the production of pro-inflammatory mediators (e.g., TNF-α, IL-6, NO) at both transcriptional and translational levels. These inhibitory effects are likely to occur via the suppression of nuclear factor kappa B (NF-κB) activation by reducing the p65 nuclear translocation but not its phosphorylation or protein expression. Calcaratarin D exhibited significantly greater inhibition of NF-κB activation than andrographolide, a well-known NF-κB inhibitor from the labdane family, suggesting that a normal-configuration labdane ring or the absence of hydroxyl groups at C-3 and C-19 positions is favorable for potent NF-κB inhibition. We further investigated the effects of calcaratarin D on the upstream signalling pathways and found that the compound selectively suppressed the LPS-induced activation of PI3K/Akt pathway without affecting much of the MAPK (i.e., ERK, JNK, and p38) activation. These findings demonstrate that calcaratarin D exerts its anti-inflammatory effects via a selective Akt-NF-κB-mediated mechanism and potentially offers a new therapeutic strategy for the management of inflammatory diseases.
- Tran, Quy T.N.,Wong, W.S. Fred,Chai, Christina L.L.
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- Synthesis and stereochemistry of the antitumor diterpenoid (+)-zerumin B
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Starting from commercially available (+)-sclareolide, the first synthesis of zerumin B was achieved by a concise, highly efficient pathway featuring stereoselective addition of a new silyloxyfuryltitanium reagent to an aldehyde intermediate and silyloxyfuran oxyfunctionalization as key steps. The synthesis established the relative and absolute configuration of zerumin B along with its identity with a purportedly new diterpenoid isolated from the plant Renealmia alpinia.
- Boukouvalas, John,Wang, Jian-Xin,Marion, Olivier,Ndzi, Bruno
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p. 6670 - 6673
(2007/10/03)
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