New methods for the synthesis of substituted nitriles

Part I of the thesis describes stereoselective chelation controlled conjugate addition of grignard reagents to hydroxy alkynenitriles. Part II describes annulation of w-halonitriles to oxa and carbocycles

Mixture synthesis of a 16-member Murisolin stereoisomer library &synthesis of C1-C20 and C21-C40 fragments of Tetrafibricin

Chapter 1 of this thesis describes two new strategies for the solution phase mixture synthesis: OEG-mixture synthesis (OMS) and OEG-fluorous mixture synthesis (OFMS). An OEG-mixture synthesis of four stereoisomers of the hydroxybutenolide unit of murisolin was pursued. A strategy for solution phase stereoisomer synthesis based on orthogonal separation tagging and double demixing was implemented with fluorous (fluoroalkyl) and oligoethylene glycol (OEG, [OCH2CH2]n) tags. A mixture of four stereoisomers of a dihydroxytetrahydrofuran subunit encoded by fluorous tags was coupled by a Kocienski-Julia olefination to a mixture of four stereoisomers of the hydroxybutenolide subunit encoded by OEG tags. An orchestrated sequence of reduction (1x), OEG demixing (1x), fluorous demixing (4x) and detagging (16x) provided sixteen stereoisomers of murisolin. Through this double tagging strategy, the configuration of sixteen compounds was encoded with only eight tags.Chapter 2 describes the synthesis of the C1-C20 and C21-C40 fragments of the natural product tetrafibricin. A convergent synthesis of the proposed structure of tetrafibricin has been explored. In this approach, we envisioned a series of the Kocienski-Julia olefination reactions with appropriate aldehydes and sulfones to afford fragments C35-C40, C31-C35 and C21-C30. The synthesis of the C35-C40 fragment has been achieved in 11 steps starting with the commercially available pent-4-en-1-ol in an overall 25% yield. The synthesis of the C31-C34 fragment commenced with the commercially available (S)-2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethanol in 5 steps in an overall 46% yield. 16 steps are implemented in the synthesis of the C21-C30 fragment in a 4.5% overall yield. The synthesis of the C14-C20 fragment was achieved in 10 steps in an overall 23% yield. A synthesis of the C9-C13 fragment was established in 5 steps in 37% overall yield. The synthesis of the C1-C8 fragment was pursued in 8 steps in an overall 22% yield. The assembly of the C1-C8, C9-C13 and C14-C20 fragments was performed to afford the C1-C20 fragment. The C21-C30, C31-C34 and C35-C40 fragments were assembled by a Kocienski-Julia olefination to form the C21-C40 fragment of tetrafibricin

Fluorous mixture synthesis of four stereoisomers of the C21-C40 fragment of tetrafibricin

Four stereoisomers of the C21-C40 fragment are synthesized in a single exercise with the aid of fluorous tagging to encode configurations at C37 and C33. After demixing and detagging, the isomers were found to have substantially identical 1H NMR spectra. However, there were some small but reliable differences in their 13C NMR spectra. © Georg Thieme Verlag Stuttgart

Sulfanylation of 1,3-dithiane anions by 5-(alkylsulfanyl)-l- phenyltetrazoles

An unusual reaction between 1,3-dithiane anions and by 5-(alkylsulfanyl)-l- phenyltetrazoles has been discovered in which the dithiane anion formally displaces the 1-phenyltetrazole ring from sulfur to provide a sulfanylated dithiane. © 2009 Institute of Organic Chemistry and Biochemistry

Synthesis of C1-C20 and C21-C40 fragments of tetrafibricin

Efficient syntheses of suitably functionalized top and bottom fragments of tetrafibricin are described. The bottom fragment is prepared by two consecutive Kocienski-Julia couplings, while the top fragment synthesis features a dithiane alkylation and a Horner-Wadsworth-Emmons reaction. © 2011 Elsevier Ltd. All rights reserved

Lower magnitude and faster waning of antibody responses to SARS-CoV-2 vaccination in anti-TNF-α-treated IBD patients are linked to lack of activation and expansion of cTfh1 cells and impaired B memory cell formationResearch in context

Summary: Background: Patients with inflammatory bowel disease (IBD) and healthy controls received primary SARS-CoV-2-mRNA vaccination and a booster after six months. Anti-TNF-α-treated patients showed significantly lower antibody (Ab) levels and faster waning than α4β7-integrin-antagonist recipients and controls. This prospective cohort study aimed to elucidate the underlying mechanisms on the basis of circulating T-follicular helper cells (cTfh) and B memory cells. Methods: We measured SARS-CoV-2- Wuhan and Omicron specific Abs, B- and T-cell subsets at baseline and kinetics of Spike (S)-specific B memory cells along with distributions of activated cTfh subsets before and after primary and booster vaccination. Findings: Lower and faster waning of Ab levels in anti-TNF-α treated IBD patients was associated with low numbers of total and naïve B cells vs. expanded plasmablasts prior to vaccination. Along with their low Ab levels against Wuhan and Omicron VOCs, reduced S-specific B memory cells were identified after the 2nd dose which declined to non-detectable after 6 months. In contrast, IBD patients with α4β7-integrin-antagonists and controls mounted and retained high Ab levels after the 2nd dose, which was associated with a pronounced increase in S-specific B memory cells that were maintained or expanded up to 6 months. Booster vaccination led to a strong increase of Abs with neutralizing capacity and S-specific B memory cells in these groups, which was not the case in anti-TNF-α treated IBD patients. Of note, Ab levels and S-specific B memory cells in particular post-booster correlated with the activation of cTfh1 cells after primary vaccination. Interpretations: The reduced magnitude, persistence and neutralization capacity of SARS-CoV-2 specific Abs after vaccination in anti-TNF-α-treated IBD patients were associated with impaired formation and maintenance of S-specific B memory cells, likely due to absent cTfh1 activation leading to extra-follicular immune responses and diminished B memory cell diversification. These observations have implications for patient-tailored vaccination schedules/vaccines in anti-TNF-α-treated patients, irrespective of their underlying disease. Funding: The study was funded by third party funding of the Institute of Specific Prophylaxis and Tropical Medicine at the Medical University Vienna. The funders had no role in study design, data collection, data analyses, interpretation, or writing of report

SARS-CoV-2 mutations in MHC-I-restricted epitopes evade CD8+ T cell responses.

CD8+ T cell immunity to SARS-CoV-2 has been implicated in COVID-19 severity and virus control. Here, we identified nonsynonymous mutations in MHC-I-restricted CD8+ T cell epitopes after deep sequencing of 747 SARS-CoV-2 virus isolates. Mutant peptides exhibited diminished or abrogated MHC-I binding in a cell-free in vitro assay. Reduced MHC-I binding of mutant peptides was associated with decreased proliferation, IFN-γ production and cytotoxic activity of CD8+ T cells isolated from HLA-matched COVID-19 patients. Single cell RNA sequencing of ex vivo expanded, tetramer-sorted CD8+ T cells from COVID-19 patients further revealed qualitative differences in the transcriptional response to mutant peptides. Our findings highlight the capacity of SARS-CoV-2 to subvert CD8+ T cell surveillance through point mutations in MHC-I-restricted viral epitopes