New sphingolipids and a sterol from a lobophytum species of the Indian ocean

Chemical investigation of a soft coral species of the genus Lobophytum has resulted in the isolation of three new sphingolipids--(2S,3S,4R)-2-nonadecanoylamino-octadecane-1,3,4-triol (1), (2S,3R,4E,8E)-[(2'R)-2'-hydroxyheptadecanoylamino]-4,8-octadecadiene-1,3-diol (2), 1-O-(beta-D-glucopyranosyl)-(2S,3R,4E,8E)-2-[(2'R)-2'-hydroxynonadecanoylamino]-9-methyl-4,8-octadecadiene-1,3-diol (3) and a sterol--(24S)-ergost-5-en-3beta,7beta-diol (4) along with the known sphingolipid--(2S,3R,4E,8E)-2-hexadecanoylamino-4,8-octadecadien-1,3-diol (5) which showed cytotoxicity against human peripheral blood mononuclear cells (PBMC).     

A Novel and Efficient One Pot Synthesis of 2,4‐Disubstituted Thiazoles and Oxazoles Using Phenyltrimethylammoniumtribromide in Ionic Liquid

A novel and efficient one‐pot procedure has been described for synthesis of 2,4‐disubstituted thiazoles and oxazoles from substituted ketones using phenyltrimethylammoniumtribromide as in situ brominating agent followed by reaction with thioamide/thiourea and amides/ureas, respectively in [bmim][BF₄] ionicliquid. The advantages of the procedure include avoiding the handling of lacrymetric compounds, hazardous and toxic organic solvents along with good to excellent yield of the products.     

Correlation of substituent effects and energy levels of the two lowest excited states of the azulenic chromophore

[structure: see text] Experimental and calculated data show that the relative energy levels of the two lowest excited states of azulene are sensitive to the nature and position of substituents on the nonalternant hydrocarbon. Extending such investigations led to a rational explanation for some of the baffling data on azulenic bacteriorhodopsin analogues in the literature.     

Structure-based drug design,synthesis and screening of MmaA1 inhibitors as novel anti-TB agents

Molecular Diversity - Tuberculosis is one of the leading causes of death across the world. The treatment regimens for tuberculosis are well established, but still the control of the disease faces...     

The nature of the delocalized cations in azulenic bacteriorhodopsin analogs.

Depending on the size and shape of their azulenic chromophores, azulenic bacteriorhodopsin (bR) pigment analogs can exist as either an initial pigment P1, a more red-shifted final pigment P2 or an equilibrium mixture of both. The absorption spectra of red-shifted bR analogs exhibit characteristic narrow-band shapes similar to charge fully delocalized cyanine-like dyes. Therefore, all such red-shifted pigments are believed to be highly delocalized, bond-equalized carbocations. We have determined structural requirements that facilitate their formation. To describe fully the red-shift potentials of these retinal analogs, we have introduced a new parameter-percent red-shift (PRS). A large PRS value not only reflects the extent of red-shift, but is also suggestive of extensive delocalization of the positive charge. Relevance of these findings in consideration of the possibility of forming stable O-intermediates is presented. The postulated resonance hybrid-like structures for different cations of the positively charged protonated Schiff base chromophores are in fact structurally distinct species, equilibrating in response to local perturbations within the supramolecular protein environment.     

The use of squaric acid as a scaffold for cofacial phenyl rings

[structure: see text] To examine the possibility of using squaric acid as a scaffold for organizing phenyl rings in a cofacial orientation, we undertook an investigation of the conformational preferences of secondary and tertiary N-phenylsquaramides. In secondary squaramides, the extended ZZ conformation is preferred, while in the N-methyl derivative, the folded EE conformation with cofacial phenyl rings is preferred. This conformational switch is likely driven by a combination of steric and electronic factors.     

Synthesis of Carbacerulenin. A General Method for Syntheses of E,E-1, 4-Dienols

The synthesis of carbacerulenin (2) by way of intramolecular cyclopropanation of a undecatriene system 8 is described.     

Cu(OTf)2 Catalyzed Synthesis of Bis(5‐methyl‐2‐furyl)methanes by Condensation of 2‐Methylfuran with Carbonyl Compounds under Solvent Free Conditions

A facile and efficient one‐pot three‐component synthesis of bis(5‐methyl‐2‐furyl)methanes has been achieved via the reaction of 2‐methylfuran with a series of aliphatic and aromatic aldehydes and aliphatic ketones in presence of copper(II) triflate under solvent free conditions. The bis(5‐methyl‐2‐furyl)methanes were obtained in 34% –72% yields and the catalyst was recycled up to four successive cycles without much loss in catalytic activity.     

New sphingolipids from marine sponge Iotrochota baculifera

Chemical examination of the marine sponge Iotrochota baculifera of the Indian Ocean furnished a sphingolipid (1), a new glycosphingolipid (iotroridoside-B, 2) and a four-component mixture of sphingolipids (3a-d) with two new components. Structure elucidation was carried out by spectral and chemical methods.     

1-Butyl-3-methylimidazolium p-toluenesulfinate: a novel reagent for synthesis of sulfones and β-ketosulfones in ionic liquid

A novel task-specific ionic liquid, 1-butyl-3-methylimidazolium p-toluenesulfinate, [bmim][p-TolSO₂] has been synthesized and used as a nucleophile for the reaction with alkyl bromides and phenacyl bromides to prepare sulfones and β-ketosulfones in excellent yields (80-93%) in [bmim][BF₄] ionic liquid. The isolated yields of sulfones and β-ketosulfones were higher in [bmim][BF₄] than other organic solvents at room temperature.