Spotlights Cite This: J. Am. Chem. Soc. 2017, 139, 15275-15275
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CHIRAL CUBIC CAGE ASSEMBLIES WITH FLUORESCENCE PROPERTIES Molecular cage assemblies are compounds that are capable of binding guest molecules in solution. They have been demonstrated for applications including molecular sensing, chemical separation, and catalysis. Chiral cage compounds are of particular interest because their structural complexity may result in enhanced functionality. Although chiral cage compounds are typically constructed from chiral precursors, in a new report, researchers led by Yu Wang and Xiaoyu Cao create chiral cubic cage assemblies from achiral molecules (DOI: 10.1021/jacs.7b07657). This alternative strategy for the creation of chiral organic cages is made possible by combining the molecular building blocks through imine formation in a manner that restricts their rotational configuration, resulting in a range of conformers. The researchers separate out four of the isomers with chiral HPLC and characterize each assembly. They find that in addition to the generation of chirality, some of the isomers created exhibit strong fluorescence, even in dilute solutions with various solvents. The study provides insight into the construction of chiral cages by rational design, combining experimental and mathematical methods, and may lead to the development of additional supramolecular assemblies and polyhedral cages from achiral building blocks. Christine Herman, Ph.D.
BORON AND ELECTROPHILES GO HAND IN HAND Tandem coupling reactions that stereoselectively construct multiple carbon−carbon bonds rapidly build molecular complexity through a single synthetic process. These methods, designed to improve synthetic efficiency, often suffer from reagent incompatibility, poor chemoselectivity, and lack of stereocontrol. Thus, efforts have focused on identifying new conjunctive reagents to overcome these limitations. Simon Meek and colleagues describe a new conjunctive coupling strategy that forms two carbon−carbon bonds and establishes an sp3-C stereocenter in a single operation (DOI: 10.1021/jacs.7b09309). The three-component Cu-catalyzed system utilizes a diborylmethane reagent as the conjunctive C1 synthon to link epoxide and allyl electrophiles, generating 1,3hydroxy-homoallyl-boronates with high levels of diastereoselectivity. The method tolerates a range of terminal and internal epoxides as well as substituted allyl and dienyl bromides. The boronate products undergo a variety of stereospecific functionalization reactions, highlighting the utility of the reported work. The highly modular and selective tandem coupling strategy offers new opportunities in asymmetric synthesis that will prove useful for developing efficient routes to complex bioactive molecules. Nicole Camasso, Ph.D.
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“SWEET” NANOPARTICLES: INFLUENCE OF SUGARS ON CELLULAR UPTAKE In order to recognize, communicate with, and adhere to other cells, some bacteria and animal cells present a fuzz-like coating composed of glycoproteins and glycolipidsknown as the glycocalyx. To mimic the glycocalyx in a laboratory setting, researchers have developed methods for preparing glyconanoparticles from glycopolymers presenting various sugars. Guosong Chen and co-workers take an in-depth look at how the topological presentation of sugars on nanoparticles causes different biological effects (DOI: 10.1021/jacs.7b07768). Specifically, the team explores how changes in the architecture of the glyco-nanoparticles affect cellular uptake by macrophage cells and binding to carbohydrate-binding proteins known as lectins. The researchers create a series of glyco-nanoparticles made from a biodegradable polyester backbone and decorated with galactoside or mannoside pendants. They find that nanoparticles presenting both glycopolymers are more efficient at cellular uptake and lectin binding than particles presenting only a single sugar component. Surprisingly, the most efficient particles are those composed of copolymer chains each presenting both sugars, which the authors attribute to an increase in sugar−receptor interactions based on architectural differences. This study adds to our understanding of how architecture can influence interactions between glycocalyxmimicking nanoparticles and proteins and cells. Christine Herman, Ph.D.
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CHEMICAL SYNTHESIS HELPS ELUCIDATE THE ROLE OF GUT BACTERIA IN COLORECTAL CANCER Does the gut microbiome play a role in colorectal cancer? Scientists have shown that some strains of the bacteria Escherichia coli in the gut make small molecules that have been implicated as potential genotoxins. These molecules, called colibactins, are thought to introduce double-strand breaks in DNA that can encourage tumor formation. But because researchers have not been able to directly isolate colibactins from bacterial cultures, it has been challenging to understand their structures, how bacteria make them, and how they may do this damage. In a Perspective, Alan Healy and Seth Herzon examine chemical synthetic studies that have begun to address some of these questions for colibactins as well as their biosynthetic precursors called precolibactins (DOI: 10.1021/jacs.7b07807). These approaches augment previous genetic investigations related to the bacterial gene cluster encoding the molecules. One notable finding shows that deletion of the gene encoding a specific peptidase in the clustercolibactin peptidaseinduces large changes in the structures of the molecules that are isolated from the bacteria. This deletion was postulated to promote accumulation of precolibactins, but it also inadvertently activates a reaction pathway that produces nongenotoxic pyridone-based molecules. The work provides an excellent example of the power of synthetic organic chemistry in answering questions in biology. Deirdre Lockwood, Ph.D. © 2017 American Chemical Society
Published: November 1, 2017 15275
DOI: 10.1021/jacs.7b11292 J. Am. Chem. Soc. 2017, 139, 15275−15275
