β-Cyclodextrin in Water: Highly Versatile and Green Approach for Biomimetic Regioselective Ring Opening of Chalcone Epoxides with Nitrogen Heterocycles

The formation of new C-C bond through highly regioselective ring opening of chalcone epoxides to nitrogen-containing heterocycles has been effectively worked out in impressive yields with heterocyclic nucleophiles such as pyrrole, indole, and 2-methyl indole in the presence of β-cyclodextrin using water as solvent at room temperature within 25–50 min. Water, an environmentally friendly reaction medium, has been utilized for the first time for the reaction of these heterocyclic nucleophiles with chalcone epoxides as their β-cyclodextrin complexes to afford 1,3-diaryl-2-hydroxy-3-(1H-3-indolyl/2-pyrrolyl)propan-1-ones (3a–u). The catalyst can be easily recovered and recycled for several times without loss of activity.     

Facile stereoslective synthesis of spiro[indole-oxiranes] by combination of phase transfer catalyst and ultrasound irradiation and their bioassay

An alternative and environmentally benign pathway for diastereoslective synthesis of fluorinated spiro[indole-3,2'-oxirane]-3'-benzoyl-2(1H)-ones (2a-g) is reported. The spiro[indole-3,2'-oxiranes] derivatives were obtained in 90-97% yield exclusively via the epoxidation of 3-aroylmethylene indole-2-ones with 30% aqueous hydrogen peroxide using cetyltrimethyl ammonium bromide as a phase transfer catalyst under ultrasound irradiation. The lead compounds have been tested for their antimicrobial activity and antioxidant properties.     

First Synthesis of N‐Substituted Amino and N‐Sulfonylaminated Methylthiopyrimidines: Reaction of Dimethyl N‐Cyanodithioiminocarbonate With Substituted Hydrazides

A novel and efficient method for the synthesis of a new variety of methylsulfanylpyrimidines by the reaction of dimethyl N‐cyanodithioiminocarbonate with substituted hydrazides. The synthetic potential of the method is demonstrated.     

Structure of lithium (picrate) (2,2′-bipyridyl)

The title compound C₁₆H₁₀N₅O₇Li is triclinic, witha=14.51(1),b=6.90(2),c=9.10(1) Å,=101.5(1),=67.1(2), =105.6°(1),Z=2 and space groupP¯1. Data were measured by photographic methods. The structure was solved by direct methods, and refined by full matrix least-squares. The refinement, based on 1337 reflections, gave the rather highR value of 0.11 because of poor quality data. The complex is dimeric. The coordination around the cation is distorted square-pyramidal. Two coordination sites are occupied by the nitrogen atoms of the bipyridyl ligand, two by the phenolic oxygen and oxygen ofo-nitro group, and the fifth coordination site is occupied by the phenolic oxygen belonging to the symmetry-related molecule (1–x,–y,1–z). Both oxygens act as bridges to form the dimer. The bridging is unsymmetrical, with Li-O (phenolic)=1.84(2) Å and Li¹-O (phenolic)=2.16(2) Å (whereI=1–x,–y, 1–Z).     

Effect of phosphate on sorption of Eu(III) by montmorillonite

Eu(III) sorption by Na-montmorillonite, the principal component of bentonite, has been studied in absence and presence of phosphate under varying experimental conditions of pH, metal ion, phosphate and sorbent concentration. The sorption edge was found to shift to high pH with decreasing sorbent concentration indicating site heterogeneity on the clay. Eu(III) sorption by Na-montmorillonite was found to increase in presence of phosphate at lower sorbent concentration of 0.5 g/L while at higher sorbent loading no effect of phosphate was observed. ATR–FTIR spectroscopy has been used to understand transition from surface complexation to surface precipitation with decreasing sorbent concentration.     

Alkene–Azide 1,3‐Dipolar Cycloaddition as a Trigger for Ultrashort Peptide Hydrogel Dissolution

An alkene–azide 1,3‐dipolar cycloaddition between trans‐cyclooctene (TCO) and an azide‐capped hydrogel that promotes rapid gel dissolution is reported. Using an ultrashort aryl azide‐capped peptide hydrogel (PhePhe), we have demonstrated proof‐of‐concept where upon reaction with TCO, the hydrogel undergoes a gel–sol transition via 1,2,3‐triazoline degradation and 1,6‐self‐immolation of the generated aniline. The potential application of this as a general trigger in sustained drug delivery is demonstrated through release of encapsulated cargo (doxorubicin). Administration of TCO resulted in 87 % of the cargo being released in 10 h, compared to 13–14 % in the control gels. This is the first example of a potential bioorthogonal‐triggered hydrogel dissolution using a traditional click‐type reaction. This type of stimulus could be extended to other aryl azide‐capped hydrogels.     

Synthesis,SAR and in vitro therapeutic potentials of thiazolidine-2,4-diones

Background

Thiazolidinedione is a pentacyclic moiety having five membered unsaturated ring system composed with carbon, oxygen, nitrogen and sulfur molecules at 1 and 3 position of the thiazole ring and widely found throughout nature in various form. They favourably alter concentration of the hormones secreted by adipocytes, particularly adiponectin. They also increase total body fat and have mixed effects on circulating lipids. Thiazolidinedione nucleus is present in numerous biological moieties and has different pharmacological activities likes, e.g. antimalarial, antimicrobial, antimycobacterial, anticonvulsant, antiviral, anticancer, anti-inflammatory, antioxidant, anti-HIV (human immunodeficiency virus) and antituberculosis.

Results and discussion

The synthesized compounds were screened for their in vitro antimicrobial potential against Gram (positive and negative) bacterial and fungal strains by tube dilution technique. In this series, compound 10 exhibited significant antimicrobial activity against B. subtilis and S. aureus with MIC?=?4.2?×?10^?2 µM/ml, compound 15 showed significant activity against K. pneumonia with MIC?=?2.60?×?10^?2 µM/ml and compound 4 displayed potent antibacterial activity against E. coli with MIC?=?4.5?×?10^?2 µM/ml. Compound 10 had most potent antifungal activity against C. albicans and A. niger with MIC?=?4.2?×?10^?2 µM/ml. Compounds 12 and 15 were found as most active antidiabetic agents having IC₅₀?=?27.63 μg/ml and 22.35 μg/ml, respectively, using DPPH assay. Antioxidant activity results indicated that compounds 3 and 9 displayed good antioxidant agent with IC₅₀?=?29.04 μg/ml and 27.66 μg/ml respectively, using α amylase assay.

Conclusion

All the synthesized derivatives exhibited good antimicrobial, antidiabetic and antioxidant activities using specific methods then compared with mentioned standard drugs. Especially, compounds 3, 4, 9, 10, 12 and 15 displayed highest activity. Structure activity relationship demonstrated that presence of electron withdrawing group (o-NO₂, p-Cl, p-Br) enhanced the antibacterial activity against E. coli as well as increased the antioxidant activity while the presence of electron releasing group (o/p-OCH₃, 3,4,5-trimethoxy) enhanced the antibacterial activity against S. aureus, B. subtilis, S. typhi, K. pneumonia, C. albicans and A. niger as well as the antidiabetic activity.

     

Titanocene(III) chloride mediated radical induced allylation of aldimines: formal synthesis of C-linked 4'-deoxy aza-disaccharide

Titanocene(III) chloride (Cp(2)TiCl) mediated radical induced allylation of aldimines for the preparation of homoallyl amines is described. The radical was generated from the allyl bromide using Cp(2)TiCl as the radical source. Formal synthesis of C(4)-C(5')-linked 4'-deoxy aza-disaccharide is demonstrated and a study toward the bicyclic skeleton of alkaloids was also accomplished. The radical initiator Cp(2)TiCl was prepared in situ from commercially available titanocene dichloride (Cp(2)TiCl(2)) and Zn dust in THF under argon.     

Model for vibrational relaxation: Pure-dephasing and depopulation

The three dominant mechanisms giving major contributions to vibrational relaxation in molecular systems are (a) pure dephasing, (b) depopulation (or energy relaxation), and (c) resonant transfer. Here (c) is not considered but the effects due to thesimultaneous occurrence of (a) and (b) are treated within a stochastic model. In dealing with (a), the vibrational frequency is assumed to undergo random uncorrelated ‘jump’, due to fluctuations in the environment of the active molecule between a continuous set of values. The ensuing results are somewhat different from those of the commonly used Kubo model of vibrational dephasing, especially at long times and appear to be better suited in interpreting certain experimental data. The model is next extended to include the simultaneous occurrence of (b). The calculation leads to two important conclusions: (i) the lineshape is not just the convolution of those due to (a) and (b), and (ii) the lineshape is asymmetric, if the intermolecular interactions are not isotropic.     

In-situ probe of gate dielectric-semiconductor interfacial order in organic transistors: origin and control of large performance sensitivities

Organic thin film transistor (OTFT) performance is highly materials interface-dependent, and dramatic performance enhancements can be achieved by properly modifying the semiconductor/gate dielectric interface. However, the origin of these effects is not well understood, as this is a classic "buried interface" problem that has traditionally been difficult to address. Here we address the question of how n-octadecylsilane (OTS)-derived self-assembled monolayers (SAMs) on Si/SiO(2) gate dielectrics affect the OTFT performance of the archetypical small-molecule p-type semiconductors P-BTDT (phenylbenzo[d,d]thieno[3,2-b;4,5-b]dithiophene) and pentacene using combined in situ sum frequency generation spectroscopy, atomic force microscopy, and grazing incidence and reflectance X-ray scattering. The molecular order and orientation of the OTFT components at the dielectric/semiconductor interface is probed as a function of SAM growth mode in order to understand how this impacts the overlying semiconductor growth mode, packing, crystallinity, and carrier mobility, and hence, transistor performance. This understanding, using a new, humidity-specific growth procedure, leads to a reproducible, scalable process for highly ordered OTS SAMs, which in turn nucleates highly ordered p-type semiconductor film growth, and optimizes OTFT performance. Surprisingly, the combined data reveal that while SAM molecular order dramatically impacts semiconductor crystalline domain size and carrier mobility, it does not significantly influence the local orientation of the overlying organic semiconductor molecules.