Synthesis of (–)-Kopsifoline A and (+)-Kopsifoline E

We report the first total synthesis of (–)-kopsifoline A and (+)-kopsifoline E. Our synthetic strategy features a biogenetically inspired regioselective C17-functionalization of a versatile intermediate containing the pentacyclic core of aspidosperma alkaloids. While this advance intermediate provides (–)-kopsifoline D via C3–C21 bond formation, regioselective C17-boronation of its indoline substructure prior to introduction of the F-ring enables access to (–)-kopsifoline A and (+)-kopsifoline E. The vinylogous urethane substructure of the key intermediate was critical in C17-boronation over a competing C7-boronation in related indole derived substrates. After oxidation of the C17–B bond to introduce the C17-ether, the C3–C21 bond of the targets is secured under the Mitsunobu reaction conditions with the vinylogous urethane as the nucleophilic component.

Concise Large-Scale Synthesis of Tomatidine, A Potent Antibiotic Natural Product

Tomatidine has recently generated a lot of interest amongst the pharmacology, medicine, and biology fields of study, especially for its newfound activity as an antibiotic agent capable of targeting multiple strains of bacteria. In the light of its low natural abundance and high cost, an efficient and scalable multi-gram synthesis of tomatidine has been developed. This synthesis uses a Suzuki–Miyaura-type coupling reaction as a key step to graft an enantiopure F-ring side chain to the steroidal scaffold of the natural product, which was accessible from low-cost and commercially available diosgenin. A Lewis acid-mediated spiroketal opening followed by an azide substitution and reduction sequence is employed to generate the spiroaminoketal motif of the natural product. Overall, this synthesis produced 5.2 g in a single pass in 15 total steps and 15.2% yield using a methodology that is atom economical, scalable, and requires no flash chromatography purifications.

Successful Photorefractive Keratectomy in a Case of Wilson’s Disease

Purpose. To report a female with a history of Wilson’s disease who underwent a successful photorefractive keratectomy (PRK) for myopic correction. Case Presentation. A twenty-year-old female with a history of Wilson’s disease and D-penicillamine use was referred to our clinic for myopic refractive surgery. Her best-corrected visual acuity (BCVA) was 20/20 for both eyes with a refraction of ‐ 1.25 ‐ 0.5 ∗ 75 ° and ‐ 1.25 ‐ 0.25 ∗ 55 ° for the right and left eyes. The slit examination showed a prominent Kayser-Fleischer ring (K-F ring) in both eyes. She underwent a successful myopic PRK surgery, and her BCVA became 20/20 with no significant refraction. Conclusions. In this report, we report a successful PRK surgery for myopic correction in a case of Wilson’s disease with prominent K-F rings in both eyes.

Magnetosphere-Ionosphere-Thermosphere Coupling study at Saturn Based on Cassini high-latitude and Grand Finale Orbits and Modelling Tools

<p class="western" lang="en-US" align="justify">The dynamics of the Kronian magnetosphere is controlled by the complex interplay of the planet’s fast rotation, its solar-wind interaction and its main plasma sources at Enceladus and other moons. At the ionospheric level, these MIT coupling processes can be characterized by a set of key parameters which include ionospheric conductances, currents and electric fields, exchanges of particles along field lines and auroral emissions. Knowledge of these key parameters in turn makes it possible to estimate the net deposition/extraction of momentum and energy into/out of the Kronian upper atmosphere. In this talk we will apply to Cassini high-inclination, F-ring and Grand Finale orbits the method developed and tested by Wang et al. (JGR 2021, under review) for Juno studies. We will combine Cassini multi-instrument data (MAG, CAPS, MIMI, UVIS and RPWS) with adequate modelling tools and data bases to retrieve these key parameters along the Cassini magnetic footprint and across the north and south auroral ovals. We will present preliminary distributions of conductances, electric currents and electric fields obtained from these orbits and will compare them with model predictions.</p>

Electrostatic Dust-Acoustic Rogue Waves in an Electron Depleted Dusty Plasma

The formation of gigantic dust-acoustic (DA) rouge waves (DARWs) in an electron depleted unmagnetized opposite polarity dusty plasma system is theoretically predicted. The nonlinear Schrödinger equation (NLSE) is derived by employing the reductive perturbation method. It is found that the NLSE leads to the modulational instability (MI) of DA waves (DAWs), and to the formation of DARWs, which are caused by to the effects of nonlinearity and dispersion in the propagation of DAWs. The conditions for the MI of DAWs and the basic properties of the generated DARWs are numerically identified. It is also seen that the striking features (viz., instability criteria, amplitude and width of DARWs, etc.) of the DAWs are significantly modified by the effects of super-thermality of ions, number density, mass and charge state of the plasma species, etc. The results obtained from the present investigation will be useful in understanding the MI criteria of DAWs and associated DARWs in electron depleted unmagnetized opposite polarity dusty plasma systems like Earth’s mesosphere (where the D-region plasma could suffer from electron density depletion), cometary tails, Jupiter’s magnetosphere, and F-ring of Saturn, etc.

Ambipolar electrostatic field in negatively charged dusty plasma

<p>It is well known that in the magnetosphere of the outer planets (eg. Saturn, Jupiter, Neptune), even in the absence of an electric current, a polarization electric field develops as a consequence of charge separation in a plasma, providing a restoring force to maintain charge neutrality. It is also well established that certain regions of these planetary systems (ionosphere, icy moons, rings) are populated by significant amount of charged dust that play an important role in the physical and chemical processes in the surrounding plasma environment.<br>In the present work, we study the effect of the charged dust grains on the polarization electric field using Saturn’s F-ring region as a case study. We derive a general expression for E parallel to the magnetic field (E_para) and then using the Cassini RPWS/LP measurements we estimate for the first time in situ E_para close to Janus/Epimetheus ring during the F ring grazing orbits. We further demonstrate that the presence of charged dust,  as small as nanometers in size, can significantly influence the plasma transport processes, in particular the ambipolar diffusion along the magnetic field lines. We show that, close to the ring plane (Z <0.1 Rs), the dusty plasma amplifies E_para by at least one order of magnitude and reverses its direction. Such a reversal implies a confinement of the electrons above the equatorial plane. Furthermore, we show a clear correlation between the amplification of the ambipolar eletrostatic field and the ions and electrons number densities, that could be used in other dusty environments where in-situ measurements are not available yet (in our solar system or the interstellar medium).</p>

Value of Kayser-Fleischer ring as a diagnostic tool for Wilson’s disease in children

The Kayser-Fleischer(K-F) ring is the hallmark of Wilson’s disease (WD). In most adults or older children, the diagnosis of Wilson’s disease may be made easily when K-Frings and low ceruloplasmin levels are present. In this study presence of K-F ring has been evaluated among children with liver disease in Bangladesh to improve the management of Chronic liver disease due to WD and reduce complications. This cross-sectional study was carried out at the Department of Paediatric Gastroenterology and Nutrition, BSMMU, Dhaka on 60 children presented with liver disease. Thirty children over three years of age considered as cases (Group-I) and thirty children with non- Wilsonian liver disease as control (Group-II). Slit lamp examination for K-F ring and twenty-four hour urinary copper excretion after giving one gram d-penicillamine 12-hour apart were done in each patient. The efficacy of K-F ring was studied. Mean age of WD patients was 8.9± 2.78 years, with a male female ratio of 1.3: 1. There was significant low level of serum ceruloplasmin in 93.33% of cases (p<.001). After penicillamine challenge, 24-hour urinary copper excretion was found significantly higher in patients with WD (median 3626.5±1698 μg/24h, range 1262- 195000) than non-Wilsonian liver disease (median 450±278.09 μg/24-h, range 47- 2062 μg/24h), (p<.001). K-F ring was found in 15 (50%) patients, absent in all patients of non-Wilsonian liver disease group and the difference was statistically significant (p<.001). Evaluation of Kayser-Fleischer ring is still a very essential diagnostic tool and is a non-invasive, affordable way to assist in the diagnosis of a potentially fatal disease.

Synthetic Study on Acremoxanthone A, Part 2: Model Study on the EFG Xanthone Moiety through a Nitrile Oxide Cycloaddition–SNAr Sequence

Toward a total synthesis of acremoxanthone A, we report a model study on the construction of the EFG ring system. The key steps include (1) an intermolecular 1,3-dipolar cycloaddition of an aryl nitrile oxide with a dienone, and (2) an SNAr reaction for construction of the F ring.