The [(DABCO)₇·(LiCH₂SiMe₃)₈] Octamer: More Aggregated than the Parent Starting Material [LiCH₂SiMe₃]₆ but Also Higher in Reactivity

Herein, we report on the reaggregation of hexameric trimethylsilylmethyllithium [LiCH₂SiMe₃]₆ with the donor base DABCO (1,4-diazabicyclo[2.2.2]­octane) to give the unprecedented octamer [(DABCO)₇·(LiCH₂SiMe₃)₈] (<b>1</b>). The structure consists of four dimers, forming Li₂C₂ four-membered rings, connected to two [(DABCO)₃·{(LiCH₂SiMe₃)₂}₂] chain fractions, interconnected by a single DABCO molecule. Interestingly, two different conformers of (LiCH₂SiMe₃)₂ dimers are present, caused by different steric demand. Higher steric strain in the center of the molecule causes an ecliptic arrangement of the Me₃Si group along the Si–C_α bond, while at the periphery the more relaxed staggered conformation is enabled. The reactivity of trimethylsilylmethyllithium coordinated by DABCO was tested in the benchmark reaction with toluene. Although the aggregation of <b>1</b> is much higher than that of the parent [LiCH₂SiMe₃]₆, the reactivity of the first is higher than that of the starting material, provided the octameric aggregation found in the solid state is maintained in nondonating solvents. While the hexamer would not react with toluene, the octamer gives benzyllithium, coordinated by DABCO. The reaction was monitored by ¹H NMR spectroscopy. Revisiting that known structure with modern technology revealed that [(DABCO)·(LiCH₂Ph)]_∞ (<b>2</b>) crystallizes in the space group <i>P</i>2₁. <b>2</b> still is the only benzyllithium compound featuring the η³-coordination mode to the C_<i>ortho</i> atom of the phenyl ring, presumably triggered by the singly donating DABCO molecule. More donor centers supersede this extra coordination to the carbanion

DataSheet_1_Extracellular Vesicle Associated miRNAs Regulate Signaling Pathways Involved in COVID-19 Pneumonia and the Progression to Severe Acute Respiratory Corona Virus-2 Syndrome.zip

BackgroundExtracellular vesicles (EVs) are mediators of cell-to-cell communication in inflammatory lung diseases. They function as carriers for miRNAs which regulate mRNA transcripts and signaling pathways after uptake into recipient cells. We investigated whether miRNAs associated with circulating EVs regulate immunologic processes in COVID-19.MethodsWe prospectively studied 20 symptomatic patients with COVID-19 pneumonia, 20 mechanically ventilated patients with severe COVID-19 (severe acute respiratory corona virus-2 syndrome, ARDS) and 20 healthy controls. EVs were isolated by precipitation, total RNA was extracted, profiled by small RNA sequencing and evaluated by differential gene expression analysis (DGE). Differentially regulated miRNAs between groups were bioinformatically analyzed, mRNA target transcripts identified and signaling networks constructed, thereby comparing COVID-19 pneumonia to the healthy state and pneumonia to severe COVID-19 ARDS.ResultsDGE revealed 43 significantly and differentially expressed miRNAs (25 downregulated) in COVID-19 pneumonia when compared to controls, and 20 miRNAs (15 downregulated) in COVID-19 ARDS patients in comparison to those with COVID-19 pneumonia. Network analysis for comparison of COVID-19 pneumonia to healthy controls showed upregulated miR-3168 (log2FC=2.28, padjustedadjusted=0.003) and targeted interleukin-8 (CXCL8) in a completely activated network. Toll-like receptor 4 (TLR4) was inhibited in COVID-19 pneumonia by miR-146a-5p and upregulated in ARDS by let-7e-5p.ConclusionEV-derived miRNAs might have important regulative functions in the pathophysiology of COVID-19: CXCL8 regulates neutrophil recruitment into the lung causing epithelial damage whereas activated TLR4, to which SARS-CoV-2 spike protein binds strongly, increases cell surface ACE2 expression and destroys type II alveolar cells that secrete pulmonary surfactants; both resulting in pulmonary-capillary leakage and ARDS. These miRNAs may serve as biomarkers or as possible therapeutic targets.</p