[¹⁸F]fluorination of biorelevant arylboronic acid pinacol ester scaffolds synthesized by convergence techniques

Aim: The development of small molecules through convergent multicomponent reactions (MCR) has been boosted during the last decade due to the ability to synthesize, virtually without any side-products, numerous small drug-like molecules with several degrees of structural diversity.(1) The association of positron emission tomography (PET) labeling techniques in line with the “one-pot” development of biologically active compounds has the potential to become relevant not only for the evaluation and characterization of those MCR products through molecular imaging, but also to increase the library of radiotracers available. Therefore, since the [18F]fluorination of arylboronic acid pinacol ester derivatives tolerates electron-poor and electro-rich arenes and various functional groups,(2) the main goal of this research work was to achieve the 18F-radiolabeling of several different molecules synthesized through MCR. Materials and Methods: [18F]Fluorination of boronic acid pinacol esters was first extensively optimized using a benzaldehyde derivative in relation to the ideal amount of Cu(II) catalyst and precursor to be used, as well as the reaction solvent. Radiochemical conversion (RCC) yields were assessed by TLC-SG. The optimized radiolabeling conditions were subsequently applied to several structurally different MCR scaffolds comprising biologically relevant pharmacophores (e.g. β-lactam, morpholine, tetrazole, oxazole) that were synthesized to specifically contain a boronic acid pinacol ester group. Results: Radiolabeling with fluorine-18 was achieved with volumes (800 μl) and activities (≤ 2 GBq) compatible with most radiochemistry techniques and modules. In summary, an increase in the quantities of precursor or Cu(II) catalyst lead to higher conversion yields. An optimal amount of precursor (0.06 mmol) and Cu(OTf)2(py)4 (0.04 mmol) was defined for further reactions, with DMA being a preferential solvent over DMF. RCC yields from 15% to 76%, depending on the scaffold, were reproducibly achieved. Interestingly, it was noticed that the structure of the scaffolds, beyond the arylboronic acid, exerts some influence in the final RCC, with electron-withdrawing groups in the para position apparently enhancing the radiolabeling yield. Conclusion: The developed method with high RCC and reproducibility has the potential to be applied in line with MCR and also has a possibility to be incorporated in a later stage of this convergent “one-pot” synthesis strategy. Further studies are currently ongoing to apply this radiolabeling concept to fluorine-containing approved drugs whose boronic acid pinacol ester precursors can be synthesized through MCR (e.g. atorvastatin)

Microscopy Conference 2021 (MC 2021) - Proceedings

Das Dokument enthält die Kurzfassungen der Beiträge aller Teilnehmer an der Mikroskopiekonferenz "MC 2021"

Deciphering the role of the gut microbiome in autoimmune thyroid disease

The aetiology of hyperthyroid Graves’ disease (GD) is incompletely understood. I hypothesized that the gut microbiome affects tolerance to the thyrotropin receptor (TSHR) leading to GD and associated Graves’ orbitopathy (GO). My work comprises two observational studies and two interventional trials, applied to a GD/GO mouse model and GD/GO patients. I applied metataxonomics (16S rRNA gene sequencing) to samples from TSHRimmunised mice from two independent laboratories and observed significant differences in alpha-diversity, beta-diversity and taxonomic profiles. I also compared TSHR-treated and control mice in one centre and identified disease-associated taxonomies (i.e. reduced Bacteroidetes and enriched Firmicutes), correlating with orbital-adipogenesis in diseased but not controls. Changes in gut microbiota taxonomy (e.g. reduced Bacteroides/increased Roseburia spp. and increased Firmicutes:Bacteroidetes ratio) were also observed in GD (n=59) and GO (n=46) patients compared with controls (n=41), and associated with hyperthyroidism or GO severity. Moreover, GD/GO patients-predicted metagenomic pathways included increased “Bacterial epithelial invasion” and “glycosaminoglycan synthesis”. The role of the gut-microbiota in TSHR-induced GD/GO was confirmed by manipulating it in early life using antibiotics which enriched Bacteroides spp. and reduced/ablated disease symptoms. The faecal material transplant from GO patients, despite showing similarities with the GO patients gut microbiota, did not exacerbate murine GO, which also remained unaffected by probiotics. In contrast, in a randomised trial, GD/GO patients receiving probiotics (in addition to anti-thyroid therapy) displayed a more stable gut microbiota composition and sustained improvement in thyroid hormone levels compared with placebo. My results illustrate significant perturbation in the gut microbiota in TSHR-induced murine GD/GO and patients with spontaneous disease. Furthermore, the similarities in differential abundance and disease-associated taxonomies noted in both species support their relevance to disease. Future studies are needed to dissect the mechanistic role of the gut microbiome in activating the immune system and determining the onset of GD/GO