H-bond to deliver fluoride: Simple fluoride salts are theoretically convenient reagents for carbon-fluorine bond formation. In practice, they are often insoluble in the solvents that dissolve their reaction partners. Pupo et al. developed urea-based catalysts that make fluoride soluble through hydrogen bonding. Moreover, their chiral substituents bias the reaction toward one of two mirror image products of C–F bond formation. This strategy should be applicable to the asymmetric addition of other salts, too. Science , this issue p. 638

Synthetic carbon allotropes such as graphene¹, carbon nanotubes² and fullerenes³ have revolutionized materials science and led to new technologies. Many hypothetical carbon allotropes have been discussed⁴, but few have been studied experimentally. Recently, unconventional synthetic strategies such as dynamic covalent chemistry⁵ and on-surface synthesis⁶ have been used to create new forms of carbon, including γ-graphyne⁷, fullerene polymers⁸, biphenylene networks⁹ and cyclocarbons^10,11. Cyclo[N]carbons are molecular rings consisting of N carbon atoms^12,13; the three that have been reported to date (N = 10, 14 and 18)^10,11 are doubly aromatic, which prompts the question: is it possible to prepare doubly anti-aromatic versions? Here we report the synthesis and characterization of an anti-aromatic carbon allotrope, cyclo[16]carbon, by using tip-induced on-surface chemistry⁶. In addition to structural information from atomic force microscopy, we probed its electronic structure by recording orbital density maps¹⁴ with scanning tunnelling microscopy. The observation of bond-length alternation in cyclo[16]carbon confirms its double anti-aromaticity, in concordance with theory. The simple structure of C₁₆ renders it an interesting model system for studying the limits of aromaticity, and its high reactivity makes it a promising precursor to novel carbon allotropes¹⁵.

The root microbiota is critical for agricultural yield, with growth-promoting bacteria able to solubilise phosphate, produce plant growth hormones, antagonise pathogens and fix N₂. Plants control the microorganisms in their immediate environment and this is at least in part through direct selection, the immune system, and interactions with other microorganisms. Considering the importance of the root microbiota for crop yields it is attractive to artificially regulate this environment to optimise agricultural productivity. Towards this aim we express a synthetic pathway for the production of the rhizopine scyllo-inosamine in plants. We demonstrate the production of this bacterial derived signal in both Medicago truncatula and barley and show its perception by rhizosphere bacteria, containing bioluminescent and fluorescent biosensors. This study lays the groundwork for synthetic signalling networks between plants and bacteria, allowing the targeted regulation of bacterial gene expression in the rhizosphere for delivery of useful functions to plants.

Molecules that contain a stereogenic phosphorus atom are crucial to medicine, agrochemistry and catalysis. While methods are available for the selective construction of various chiral organophosphorus compounds, catalytic enantioselective approaches for their synthesis are far less common. Given the vastness of possible substituent combinations around a phosphorus atom, protocols for their preparation should also be divergent, providing facile access not only to one but to many classes of phosphorus compounds. Here we introduce a catalytic and enantioselective strategy for the preparation of an enantioenriched phosphorus(V) centre that can be diversified enantiospecifically to a wide range of biologically relevant phosphorus(V) compounds. The process, which involves an enantioselective nucleophilic substitution catalysed by a superbasic bifunctional iminophosphorane catalyst, can accommodate a wide range of carbon substituents at phosphorus. The resulting stable, yet versatile, synthetic intermediates can be combined with a multitude of medicinally relevant O-, N- and S-based nucleophiles.

Oligonucleotides that target mRNA have great promise as therapeutic agents for life-threatening conditions but suffer from poor bioavailability, hence high cost. As currently untreatable diseases come within the reach of oligonucleotide therapies, new analogues are urgently needed to address this. With this in mind we describe reduced-charge oligonucleotides containing artificial LNA-amide linkages with improved gymnotic cell uptake, RNA affinity, stability and potency. To construct such oligonucleotides, five LNA-amide monomers (A, T, C, 5mC and G), where the 3′-OH is replaced by an ethanoic acid group, are synthesised in good yield and used in solid-phase oligonucleotide synthesis to form amide linkages with high efficiency. The artificial backbone causes minimal structural deviation to the DNA:RNA duplex. These studies indicate that splice-switching oligonucleotides containing LNA-amide linkages and phosphorothioates display improved activity relative to oligonucleotides lacking amides, highlighting the therapeutic potential of this technology.

Herein we disclose a mild protocol for the reductive functionalisation of quinolinium and isoquinolinium salts. The reaction proceeds under transition‐metal‐free conditions as well as under rhodium catalysis with very low catalyst loadings (0.01 mol %) and uses inexpensive formic acid as the terminal reductant. A wide range of electrophiles, including enones, imides, unsaturated esters and sulfones, β‐nitro styrenes and aldehydes are intercepted by the in situ formed enamine species forming a large variety of substituted tetrahydro(iso)quinolines. Electrophiles are incorporated at the C‐3 and C‐4 position for quinolines and isoquinolines respectively, providing access to substitution patterns which are not favoured in electrophilic or nucleophilic aromatic substitution. Finally, this reactivity was exploited to facilitate three types of annulation reactions, giving rise to complex polycyclic products of a formal [3+3] or [4+2] cycloaddition.