Mechanochemistry and Eco-Bases for Sustainable Michael Addition Reactions.

The Michael addition reaction was revisited with a full focus on sustainability combined with efficiency, using mechanochemistry in mild conditions. First, the synthesis of cyclopentenone derivatives was chosen as a model reaction to find optimal conditions in mechanochemistry while using classical but weak bases. The reaction was efficient (84-95% yields), fast (2-6 h), solvent free, and required 0.

Green and Effective Preparation of α-Hydroxyphosphonates by Ecocatalysis.

A green and effective approach for the synthesis of structurally diversed α-hydroxyphosphonates via hydrophosphonylation of aldehydes under solventless conditions and promoted by biosourced catalysts, called ecocatalysts "Eco-MgZnOx" is presented. Ecocatalysts were prepared from Zn-hyperaccumulating plant species , with simple and benign thermal treatment of leaves rich in Zn, and without any further chemical treatment. The elemental composition and structure of Eco-MgZnOx were characterized by MP-AES, XRPD, HRTEM, and STEM-EDX techniques.

The Unexpected Helical Supramolecular Assembly of a Simple Achiral Acetamide Tecton Generates Selective Water Channels.

Invited for the cover of this issue is the collaborative research team coordinated by Arie van der Lee at the University of Montpellier. The image depicts chiral channels with highly mobile water molecules resulting from the robust self-organization of a simple achiral acetamide. Fully reversible release and re-uptake of water molecules takes place near ambient conditions, with efficient water transport and a good selectivity against NaCl suggesting it to be an efficient candidate for desalination processes.

Eco-Friendly Methodology for the Formation of Aromatic Carbon-Heteroatom Bonds by Using Green Ionic Liquids.

A new sustainable method is reported for the formation of aromatic carbon-heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl hexahydrate.

Manipulation of Transmembrane Transport by Synthetic K Ionophore Depsipeptides and Its Implications in Glucose-Stimulated Insulin Secretion in β-Cells.

The cyclic depsipeptide cereulide toxin it is a very well-known potassium electrogenic ionophore particularly sensitive to pancreatic beta cells. The mechanistic details of its specific activity are unknown. Here, we describe a series of synthetic substituted cereulide potassium ionophores that cause impressive selective activation of glucose-induced insulin secretion in a constitutive manner in rat insulinoma INS1E cells.

Imidazole derivatives as artificial water channel building-blocks: structural design influence on water permeability.

A series of mono- and di-ureidoethylimidazole derivatives were tested as self-assembled supramolecular channels for water transport. Several structural behaviours were compared in order to gain insight on the structure-water transport activity relationship. The three main features that are critical to tailor artificial water channel building blocks are: (i) the selectivity of the hydrophilic head, (ii) the H-bonding scaffold favouring the directional self-assembly, and (iii) the lipophilic tail for the compatibility with the hydrophobic environment of the lipid bilayer.

Structure-Driven Selection of Adaptive Transmembrane Na Carriers or K Channels.

Self-assembled alkyl-ureido-benzo-15-crown-5-ethers are selective ionophores for K cations, which are preferred to Na cations. The transport mechanism is determined by the optimal coordination rather than classical dimensional compatibility between the crown ether hole and the cation diameter. Herein, we demonstrate that systematic changes of the structure lead to unexpected modifications in the cation-transport activity and suffice to produce adaptive selection.

Oriented chiral water wires in artificial transmembrane channels.

Aquaporins (AQPs) feature highly selective water transport through cell membranes, where the dipolar orientation of structured water wires spanning the AQP pore is of considerable importance for the selective translocation of water over ions. We recently discovered that water permeability through artificial water channels formed by stacked imidazole I-quartet superstructures increases when the channel water molecules are highly organized. Correlating water structure with molecular transport is essential for understanding the underlying mechanisms of (fast) water translocation and channel selectivity.

Hydrophobic metallo-supramolecular PdL cages for zwitterionic guest encapsulation in organic solvents.

Hydrophilic zwitterionic guest encapsulation by metallo-supramolecular cages through synergetic coordination, H-bonding and hydrophobic interactions.

Bis-15-crown-5-ether-pillar[5]arene K-Responsive Channels.

An artificial selective K channel is formed from the supramolecular organization on bis(benzo-15-crown-5- ether-ureido)-pillar[5]arene compound. This channel achieves a selectivity of S = 5 for an initial transport rate of k = 3.2 × 10 s.

"Pyrene Box" Cages for the Confinement of Biogenic Amines.

The complete structure of non-crystalline compounds can be determined by confining them in crystalline structures. The reduced motional degrees of freedom of encapsulated guests can be obtained through their anchoring to the host cages, which results in the reduction of a significant amount of disorder. The "pyrene box" cages that easily crystallize from aqueous solutions are recommended to achieve complete structure elucidation of compounds of biological interest.

Controlled supramolecular structure of guanosine monophosphate in the interlayer space of layered double hydroxide.

Guanosine monophosphates (GMPs) were intercalated into the interlayer space of layered double hydroxides (LDHs) and the molecular arrangement of GMP was controlled in LDHs. The intercalation conditions such as GMP/LDH molar ratio and reaction temperature were systematically adjusted. When the GMP/LDH molar ratio was 1:2, which corresponds to the charge balance between positive LDH sheets and GMP anions, GMP molecules were well-intercalated to LDH.

Dynameric host frameworks for the activation of lipase through H-bond and interfacial encapsulation.

A facile lipase activation has been achieved by direct addition of multivalent amide dynameric frameworks into the reaction aqueous solutions, through the combined effects of lipase-host matrices, H-bonds and interfacial interactions.

Adaptive Encapsulation of ω-Amino Acids and Their Guanidinium-Amide Congeners.

The binding and the encapsulation of the 6-aminohexanoic acid (1) and 11-aminoundecanoic acid (2) are achieved in aqueous solution and in crystalline Pyrene-box cages. Unexpectedly, the amino-guanidinium AG and the amino acids 1 or 2 are reacting in aqueous solution in the absence and in the presence of Pyrene-box cages. The formation of an amide bond between a carboxylic acid and the amino-guanidine unit under mild acidic conditions in water without the use a coupling reagent is extremely interesting and unexpected.

Salt-Excluding Artificial Water Channels Exhibiting Enhanced Dipolar Water and Proton Translocation.

Aquaporins (AQPs) are biological water channels known for fast water transport (∼10(8)-10(9) molecules/s/channel) with ion exclusion. Few synthetic channels have been designed to mimic this high water permeability, and none reject ions at a significant level. Selective water translocation has previously been shown to depend on water-wires spanning the AQP pore that reverse their orientation, combined with correlated channel motions.

Dynamic encapsulation and activation of carbonic anhydrase in multivalent dynameric host matrices.

A straight-forward carbonic anhydrase activation strategy via dynamic encapsulation has been achieved by direct addition of multivalent amide dynamers into enzyme reaction solutions.

Squalyl Crown Ether Self-Assembled Conjugates: An Example of Highly Selective Artificial K Channels.

The natural KcsA K channel, one of the best-characterized biological pore structures, conducts K cations at high rates while excluding Na cations. The KcsA K channel is of primordial inspiration for the design of artificial channels. Important progress in improving conduction activity and K /Na selectivity has been achieved with artificial ion-channel systems.

Supramolecular rulers enabling selective detection of pure short ssDNA via chiral self-assembly.

Multivalent self-assembly of trifunctional aromatic propellers and ssDNA results in the formation of chiral supramolecular assemblies that can be used for the detection of small fragments of ssDNA with different lengths and compositions.

Highly Selective Artificial Cholesteryl Crown Ether K(+)-Channels.

The bacterial KcsA channel conducts K(+) cations at high rates while excluding Na(+) cations. Herein, we report an artificial ion-channel formed by H-bonded stacks of crown-ethers, where K(+) cation conduction is highly preferred to Na(+) cations. The macrocycles aligned along the central pore surround the K(+) cations in a similar manner to the water around the hydrated cation, compensating for the energetic cost of their dehydration.

Exclusive Hydrophobic Self-Assembly of Adaptive Solid-State Networks of Octasubstituted 9,9'-Spirobifluorenes.

An easy and powerful access to 3,3',6,6'-tetrasubstituted 9,9'-spirobifluorene derivatives with tetrahedral orientation of the peripheral groups (i.e., -I, -CN, -NO2, -CH═O, -COOH, -C≡CH, -4-Py) was developed.

Polarized Water Wires under Confinement in Chiral Channels.

The alignment of water molecules along chiral pores may activate proton/ion conduction along dipolar hydrophilic pathways. Here we show that a simple synthetic "T-channel" forms a directional pore with its carbonyl moieties solvated by chiral helical water wires. Atom-scale simulations and experimental crystallographic assays reveal a dynamical structure of water and electrolyte solutions (alkali metal chlorides) confined in these organic T-channels.