Regioselective intramolecular N1-C3 cyclizations on pyrrole-proline to ABC tricycles of dibromophakellin and ugibohlin

Pyrrole N1-C and C3-C regioselective linkage to the fused tricycle ABC system present in the marine metabolites ugibohlin and dibromoisophakellin is described. The cyclization is closely dependent on the electrophilic function, bromination degree of the pyrrole moiety and pH conditions. The mechanism of the functionalization of the ABC olefin by oxidative agents was found to occur through an N-acyliminium intermediate as showed by the natural chemical connection between ugibohlin and dibromoisophakellin.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Smenoqualone a novel sesquiterpenoid from the marine sponge Smenospongia sp.

Smenoqualone, a novel quinonic terpenoid with a rearranged drimane skeleton was isolated from a marine sponge Smenospongia sp. The stereostructure was determined by detailed analyses of ¹H and ¹³C NMR spectra, ¹H-¹H COSY, ¹H-¹³C correlations via HMQC, HMBC and NOE difference NMR experiments.     

Antioxidant benzylidene 2-aminoimidazolones from the Mediterranean sponge Phorbas topsenti

Three new benzylidene 2-aminoimidazolones, named phorbatopsins A-C, have been isolated from the Mediterranean marine sponge Phorbas topsenti, in addition to the known astaxanthin, adonirubin, taurine, and taurobetain. Their structures were elucidated through mass spectrometric and detailed 1D and 2D NMR spectroscopic data. The relative configuration of the molecules was determined on the basis of ¹H and ¹³C chemical shifts and proton-proton coupling constants. The absolute configuration of the chiral carbon C-6 of phorbatopsin B was determined by modified Mosher's method. The antioxidant activity, evaluated through the Oxygen Radical Absorbance Capacity (ORAC) assay, was also reported for the seven isolated compounds and structure-activity relationships are discussed. Phorbatopsin A appeared as the most active with an ORAC value of 0.88. Further investigations to support the promising antioxidant activity of phorbatopsin A will be followed.     

Investigating the vortex melting phenomenon in BSCCO crystals using magneto-optical imaging technique

Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals of Bi₂Sr₂CaCu₂O₈ (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local melting temperature/field, we have constructed maps of the melting landscape T _m(H, r), viz., the melting temperature (T _m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite effects on the local melting transition.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

Background

Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System) neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior.

Results

We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle.

Conclusion

Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal transport holds great promise. The data shown here provide a basic framework for the intraneural pharmacology of this tripartite complex. The pharmacologically efficacious drug delivery demonstrated here verify the fundamental feasibility of using axonal transport for targeted drug delivery.     

Novel alkaloids of the aaptamine class from an Indonesian marine sponge of the genus Xestospongia

Four novel alkaloids of the aaptamine class have been isolated in addition to the known aaptamine, isoaaptamine, demethyl(oxy)aaptamine and its dimethylketal from an unidentified species of Indonesian marine sponge of the genus Xestospongia. Their structures were elucidated on the basis of detailed 1D and 2D NMR spectroscopic data. Their antimicrobial activity was tested towards Gram (+) (S. aureus), Gram (−) (E. coli, V. anguillarum) bacterial strains, a fungus (C. tropicalis); their cytotoxic activity was evaluated against KB cells.