A Comparison of Three Different Biodegradable Aliphatic Oligoesters (PGA,PLLA, and PCL) with Similar Linear Alkyl End Groups by DSC and SAXS

The biodegradable aliphatic oligoesters polyglycolide (PGA), poly(L-lactide) (PLLA), and poly(?-caprolactone) (PCL) with similar number-average molecular weight M_n values but different linear alkyl end groups [CH₃?[CH₂?CH₂]_m?CH₂?] were compared in terms of their physical properties, parameters such as melting temperature (T_m), crystallinity (x_i), long period (L), and lamella thickness (D). They were analyzed by DSC and SAXS. The effect of a longer and nonpolar alkyl end group such as docosyl [CH₃?[CH₂?CH₂]₁₀?CH₂?] on the long period (L) was more evident for PCL because it was the most nonpolar species in the family of oligoesters analyzed.     

Cooperative Bond Activation and Catalytic Reduction of Carbon Dioxide at a Group 13 Metal Center

A single‐component ambiphilic system capable of the cooperative activation of protic, hydridic and apolar H? X bonds across a Group 13 metal/activated β‐diketiminato (Nacnac) ligand framework is reported. The hydride complex derived from the activation of H₂ is shown to be a competent catalyst for the highly selective reduction of CO₂ to a methanol derivative. To our knowledge, this process represents the first example of a reduction process of this type catalyzed by a molecular gallium complex.     

A General and Scalable Synthesis of Aeruginosin Marine Natural Products Based on Two Strategic C(sp3)H Activation Reactions

An efficient and scalable access to the aeruginosin family of marine natural products, which exhibit potent inhibitory activity against serine proteases, is reported. This synthesis was enabled by the strategic use of two different, recently implemented C(sp³)? H activation reactions. The first method led to the common 2‐carboxy‐6‐hydroxyoctahydroindole (Choi) core of the target molecules on a large scale, whereas the second one provided rapid and divergent access to the various hydroxyphenyllactic (Hpla) subunits. This strategy allowed the synthesis of the aeruginosins 98B and 298A, with the latter being obtained in unprecedentedly large quantities.     

Isolation and Total Synthesis of Kirkamide,an Aminocyclitol from an Obligate Leaf Nodule Symbiont

The new C₇N aminocyclitol kirkamide ( 1 ) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome‐driven ¹H NMR‐guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single‐crystal X‐ray crystallography. An enantioselective total synthesis was developed, which delivered kirkamide ( 1 ) on a gram scale in 11 steps and features a Ferrier carbocyclization and a Pd‐mediated hydroxymethylation. We propose that kirkamide is synthesized by Candidatus Burkholderia kirkii, the obligate leaf symbiont of Psychotria kirkii. Kirkamide ( 1 ) was shown to be toxic to aquatic arthropods and insects, thus suggesting that bacterial secondary metabolites play a protective role in the Psychotria/Burkholderia leaf nodule symbiosis.     

Direct Imaging of Octahedral Distortion in a Complex Molybdenum Vanadium Mixed Oxide

Complex Mo,V‐based mixed oxides that crystallize in the orthorhombic M1‐type structure are promising candidates for the selective oxidation of small alkanes. The oxygen sublattice of such a complex oxide has been studied by annular bright field scanning transmission electron microscopy. The recorded micrographs directly display the local distortion in the metal oxygen octahedra. From the degree of distortion we are able to draw conclusions on the distribution of oxidation states in the cation columns at different sites. The results are supported by X‐ray diffraction and electron paramagnetic resonance measurements that provide integral details about the crystal structure and spin coupling, respectively.     

Tandem Chemoselective Suzuki–Miyaura Cross‐Coupling Enabled by Nucleophile Speciation Control

Control of boronic acid speciation is presented as a strategy to achieve nucleophile chemoselectivity in the Suzuki–Miyaura reaction. Combined with simultaneous control of oxidative addition and transmetalation, this enables chemoselective formation of two C? C bonds in a single operation, providing a method for the rapid preparation of highly functionalized carbogenic frameworks.     

Whole‐Genome Sequencing of a Single Viral Species from a Highly Heterogeneous Sample

Metagenomic studies suggest that only a small fraction of the viruses that exist in nature have been identified and studied. Characterization of unknown viral genomes is hindered by the many genomes populating any virus sample. A new method is reported that integrates drop‐based microfluidics and computational analysis to enable the purification of any single viral species from a complex mixed virus sample and the retrieval of complete genome sequences. By using this platform, the genome sequence of a 5243 bp dsDNA virus that was spiked into wastewater was retrieved with greater than 96 % sequence coverage and more than 99.8 % sequence identity. This method holds great potential for virus discovery since it allows enrichment and sequencing of previously undescribed viruses as well as known viruses.     

The Unexpected Influence of Precursor Conversion Rate in the Synthesis of III–V Quantum Dots

Control of quantum dot (QD) precursor chemistry has been expected to help improve the size control and uniformity of III–V QDs such as indium phosphide and indium arsenide. Indeed, experimental results for other QD systems are consistent with the theoretical prediction that the rate of precursor conversion is an important factor controlling QD size and size distribution. We synthesized and characterized the reactivity of a variety of group‐V precursors in order to determine if precursor chemistry could be used to improve the quality of III–V QDs. Despite slowing down precursor conversion rate by multiple orders of magnitude, the less reactive precursors do not yield the expected increase in size and improvement in size distribution. This result disproves the widely accepted explanation for the shortcoming of current III–V QD syntheses and points to the need for a new generalizable theoretical picture for the mechanism of QD formation and growth.