Cutting carbons : The three‐dimensional structure of polyneuridine aldehyde esterase (PNAE) gives insight into the enzymatic mechanism of the biosynthesis of C9‐ from C10‐monoterpenoid indole alkaloids (see scheme). PNAE is a very substrate‐specific serine esterase. It harbors the catalytic triad S87‐D216‐H244, and is a new member of the α/β‐fold hydrolase superfamily. Its novel function leads to the diversification of alkaloid structures.
Protein roll call : Peptide‐based building blocks, in which both an α‐helix‐forming segment and a β‐sheet segment are located within a single macrocyclic structure, self‐assemble into α‐helix‐decorated artificial proteins. This approach provides a starting point for developing artificial proteins that can modulate α‐helix‐mediated interactions occurring in a multivalent fashion.
Taking the reins : The title transformation of thioamides and N‐diphenylphosphinoyl imines is described. By harnessing the power of cooperative catalysis between a soft Lewis acid and a hard Brønsted base, thioamide carbon pronucleophiles can furnish Mannich products (see scheme). Divergent transformation of the thioamide functionality highlights the utility of this methodology.
Bringing order : A new class of periodic mesoporous organosilicas (PMOs) with a urea‐bridged organosilica precursor under acid‐catalyzed and inorganic‐salt‐assisted conditions was obtained. The large‐pore hybrid materials have ordered mesostructure with uniform pore size distributions, which can be seen from the TEM images.
Molecular switches : Highly efficient acido‐ and photoswitchable frequency doublers (see scheme) based on the indolinooxazolidine core are studied by means of hyper‐Rayleigh experiments and quantum‐chemical calculations.
Effect of a PAH on base pairing : A polycyclic aromatic hydrocarbon (PAH) covalently linked to the N6‐position of a dangling deoxyadenosine residue (see scheme) of an oligonucleotide increases target affinity, but decreases base‐pairing selectivity. Melting point increases of up to 28 °C (14 °C per residue) were observed, and 20 out of 24 mismatch‐containing duplexes are stabilized more strongly by the PAH substituent than their perfectly matched counterpart.
A new relative of pentacene : The dialkynylated tetraazapentacene (see figure) was prepared by a two‐step synthesis from the corresponding quinone derivative. The heteroacene is an air‐stable, dark‐blue, crystalline material and is of great interest as a potential organic n‐electron‐transport material.
Positive discrimination : Chemo‐ and regioselective palladium‐catalyzed cycloetherification of allendiols, namely β,γ‐ and γ,δ‐allendiols, may occur by judicious choice of palladium‐catalyzed conditions owing to their potential ability to discriminate between both nucleophilic sites (see scheme).
Silica supports : Well‐defined silica‐supported Mo–alkylidene complexes containing one alkoxy/aryloxy substituent are selectively obtained by grafting onto silica either well‐defined molecular bis(alkoxy) or alkoxyamido complexes (see scheme). These silica‐supported complexes are highly efficient catalyst precursors for the metathesis of acyclic alkenes. However, they display poor performances in ring‐closing metathesis reactions, possibly due to the relatively large siloxy ligand (silica) inducing a greater rigidity.
Constructing α‐stereogenic amides and ketones : The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
An energy‐transfer cascade is generated from a cationic conjugated polymer (PFP) and negatively charged, Y‐shaped DNA labeled with three dyes at its termini (fluorescein (Fl), Tex Red, and Cy5). Multistep fluorescence resonance energy transfer regulates the fluorescence intensities of PFP and the dyes. Different types of logic gates can be operated by observing the emission wavelengths of different dyes with multiplex nucleases as inputs.
Exciton migration! Spectroscopic analyses and extensive molecular dynamics studies revealed a well‐defined 41 helix in which the perylene molecules (see figure) form four “helter‐skelter‐like” overlapping pathways along which excitons and electrons can rapidly migrate.
What a difference ! The energy differences between anti and syn conformers as well as the energy barrier for the rotation around the aryl–aryl bond of a number of 2,2′‐bipyridine molecules were examined by quantum‐chemical methods. The energy differences were found to be governed by the substituents directly attached to the bipyridine and their ability to form intramolecular hydrogen bonds.
Micropatterns of silica were generated under biocompatible conditions by a combination of microcontact printing (μCP), layer‐by‐layer (LbL) self‐assembly, and biomimetic silicification. Quaternary amine‐containing poly(diallyl dimethyl ammonium chloride) induced polycondensation of silicic acid, resulting in spatioselective formation of silica micropatterns. Scale bar: 10 μm.
Economical approach : The first organocatalytic asymmetric intramolecular hydroarylation of phenol‐ and aniline‐derived enals offers one of the most straightforward and atom‐economic approaches to enantioriched chromans and tetrahydroquinolines (up to 96 % ee; see scheme).
Water seeds : Complex stoichiometry/composition and degree of oligomerization (oligomeric supramolecular complex formation) of cucurbit[6]uril (CB[6]) with N‐alkyl‐ and N,N′‐dialkylpiperazine were investigated in aqueous solutions by means of isothermal titration calorimetry (ITC), ESI‐MS, NMR and light scattering measurements.
High‐de‐hydride! A straightforward reaction between a magnesium silylamido/N‐heterocyclic carbene adduct and phenylsilane provides a {Mg4H6} cluster molecule that may be regarded as a combination of two magnesium dihydride and two magnesium monohydride moieties.
