A variety of functionalized biaryls can be accessed by coupling aryl and heteroaryl esters with boronic acids in Suzuki–Miyaura‐type decarbonylative cross‐coupling catalyzed by an affordable catalyst system composed of Ni(cod)2 and PCy3. The methodology is tolerant of a variety of functional groups and presents an attractive alternative to the use of palladium catalysis currently used in industry to acquire such bis(hetero)aryls, but also reveals challenges associated with nickel catalysis of esters in cross‐coupling chemistry.
We report herein a general catalytic method for Csp(2)-Csp(3) bond formation through C-F activation. The process uses an inexpensive nickel complex with either diorganozinc or alkylzinc halide reagents, including those with β-hydrogen atoms. A variety of fluorine substitution patterns and functional groups can be readily incorporated. Sequential reactions involving different precatalysts and coupling partners permit the synthesis of densely functionalized fluorinated building blocks.
The IL-17 cytokine family is associated with multiple immune and autoimmune diseases and comprises important diagnostic and therapeutic targets. This work reports the development of epitope-targeted ligands designed for differential detection of human IL-17F and its closest homologue IL-17A. Non-overlapping and unique epitopes on IL-17F and IL-17A were identified by comparative sequence analysis of the two proteins. Synthetic variants of these epitopes were utilized as targets for in situ click screens against a comprehensive library of synthetic peptide macrocycles with 5-mer variable regions. Single generation screens yielded selective binders for IL-17F and IL-17A with low cross-reactivity. Macrocyclic peptide binders against two distinct IL-17F epitopes were coupled using variable length chemical linkers to explore the physical chemistry of cooperative binding. The optimized linker length yielded a picomolar affinity binder, while retaining high selectivity. The presented method provides a rational approach towards targeting discontinuous epitopes, similar to what is naturally achieved by many B cell receptors.
The presence of aryl C-F bonds in pharmaceuticals and agrochemicals is increasing rapidly. Incorporation of a fluorine substituent into biologically relevant molecules yields many benefits such as decreased metabolism, solubility, hydrophobicity and decreased negative side effects. Since there are no known examples of naturally occurring aryl fluorides all must be accessed through chemical synthesis. The formation and activation of aryl C-F bonds is a challenging endeavor, nevertheless several strategies are possible. Recent developments towards the synthesis of fluoroaromatics, as well as routes to selectively remove fluorine from polyfluoroaromatics are surveyed.
Chemically synthesized, small peptides that bind with high affinity and specificity to CD8-expressing (CD8+) tumorinfiltrating T cells, yet retain the desirable characteristics of small molecules, hold valuable potential for diagnostic molecular imaging of immune response. Here, we report the development of 18 F-labeled peptides targeting human CD8α with nanomolar affinity via the strain-promoted sydnone−alkyne cycloaddition with 4-[ 18 F]fluorophenyl sydnone. The 18 F-sydnone is produced in one step, in high radiochemical yield, and the peptide labeling proceeds rapidly. A hydrophilic chemical linker results in a tracer with favorable pharmacokinetic properties and improved image contrast, as demonstrated by in vivo PET imaging studies.
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