A three-component approach to isoquinoline derivatives by cycloaddition/Heck reaction sequence

Here, we report a three-component coupling reaction approach between an aldehyde, an allyloxyamine, and a maleimide toward isoquinoline derivatives. At first, an oxime O-allylic ether, prepared by dehydrative condensation of the aldehyde and the allyloxyamine, was reacted with the maleimide in the presence of a Pd²⁺ species. The cycloadduct obtained was then subjected to the Heck cyclization employing a Pd⁰ species to give thermodynamically stable diastereomer of isoquinoline derivatives selectively in 25-78% yields.     

Asymmetric reduction of aliphatic ketones and acyl silanes using chiral anti-pentane-2,4-diol and a catalytic amount of 2,4-dinitrobenzenesulfonic acid

Aliphatic ketones were reduced to the corresponding secondary alcohols by using anti-1,3-diol and a catalytic amount of 2,4-dinitrobenzenesulfonic acid (DNBSA) in benzene at reflux. Addition of 1-octanethiol in that media improved the efficiency of the reduction. Asymmetric reduction of aliphatic ketones was performed by using chiral anti-pentane-2,4-diol, and highly asymmetric induction (up to >99% ee) was observed in the reduction of tert-alkyl ketones. Asymmetric reduction of acyl silanes using chiral anti-pentane-2,4-diol and DNBSA proceeded efficiently in the absence of octanethiol and the corresponding α-silyl alcohols were obtained in high yields with high ees.     

Synthesis of a Stable N-Hetero-RhI-Metallacyclic Silanone

A novel N-hetero-Rh^I-metallacyclic silanone 2 has been synthesized. The silanone 2 , showing an extremely large dimerization energy (ΔG=+86.2 kcal mol⁻¹), displays considerable stability and persists in solution up to 60 °C. Above 120 °C, an intramolecular C_sp3−H insertion occurs slowly over a period of two weeks leading to the bicyclic silanol 5 . The exceptional stability of 2 , related to the unusual electronic and steric effects of Rh^I-substituent, should allow for a more profound study and understanding of these new species. Furthermore, the metallacyclic silanone 2 presents two reactive centers (Si=O and Rh), which can be involved depending upon the nature of reagents. Of particular interest, the reaction with H₂ starts with the hydrogenation of Rh^I center leading to the corresponding Rh^III-dihydride complex 7 and it undergoes a cis/trans-isomerization via a particular mechanism, demonstrating that addition-elimination processes can also happen for silanones just like for their carbon analogues!     

Amycolamicin: A Novel Broad‐Spectrum Antibiotic Inhibiting Bacterial Topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X‐ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans‐decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad‐spectrum antibiotic against Gram‐positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.     

Measurement of excitation-contraction coupling time in lower extremities

Objective: The aim of this study was to apply a novel method to measure excitation-contraction coupling time (ECCT) in normal soleus muscles. Methods: We performed simultaneous recordings of soleus compound muscle action potential (CMAP) and foot movement-related potential (MRP), and measured ankle plantar flexion torque in 36 healthy subjects. We calculated ECCT and examined the relations between CMAP, MRP, ECCT and ankle plantar flexion torque. Results: Statistical analyses established reference ranges (mean ± SE) for CMAP (13.4 ± 0.9 mV), MRP (5.3 ± 0.4 m/s²), ECCT (5.2 ± 0.1 ms), torque (85.9 ± 6.4 Nm) and torque/body weight (1.4 ± 0.1 Nm/kg). The torque showed a positive linear correlation with CMAP (p = 0.041) and a negative linear correlation with ECCT (p = 0.045). Conclusion: Soleus ECCT can be recorded easily, and is useful to assess the impairment of E-C coupling in muscles of the lower extremities.     

Plasma wave interactions in the microwave to THz range between carriers in a semiconductor 2DEG and interdigital slow waves

Traveling wave interactions between the plasma wave in a two-dimensional electron gas (2DEG) in the AlGaAs/GaAs high electron mobility transistor (HEMT) structure and the electromagnetic space harmonic slow waves produced by interdigital metal electrodes were investigated both theoretically and experimentally. By means of a TM mode analysis, a general expression for the ω- and k-dependent effective permittivity of the 2DEG plasma was derived. The two-terminal admittance was calculated by a Green’s function method from the microwave to the THz wave region. Occurrences of negative admittance were predicted, and its peak values increased with frequency to a very large value in the THz region due to the reduction in the number of collisions per cycle. Preliminary admittance measurements at microwave frequencies showed good agreement with calculations, confirming the existence of plasma wave interactions.