An efficient one-pot three-component synthesis and antimicrobial evaluation of tetra substituted thiophene derivatives

A convenient one-pot three-component method for the preparation of tetra-substituted thiophene derivatives has been developed. Reaction of acetyl acetone 1, phenyl isothiocynate 2 and 2-chloromethyl derivatives 3a–3c in the presence of potassium carbonate afforded the target compounds, namely ethyl2-(4-acetyl-3-methyl-5-(phenylamino)thiophen-2-yl)-2-oxoacetate derivatives 4a–4e, ethyl 3-(4-acetyl-3-methyl-5-(phenylamino)thiophen-2-yl)-3-oxopropanoate derivatives 4f–4i, di((4-acetyl-3-methyl-5-phenylamino)thiophen-2-yl)ketone derivatives 4j–4n in reasonable overall yields. The synthesized compounds were screened for antimicrobial activity. The detailed synthesis, spectroscopic data and antimicrobial activities of synthesized compounds were reported.     

Interconnections of Markov chains and quasi-reversible queuing networks

A quasi-reversible queue can be associated with certain type of transactions of a Markov chain. It is shown that if Markov chains are coupled in a certain way, then to the resulting chain be associated a queuing network which is itself quasi-reversible and the stationary distribution of the chain takes the product form. The product form for mixed networks is derived from the result for open networks.     

Single molecule conformational analysis of the biologically relevant DNA G-quadruplex in the promoter of the proto-oncogene c-MYC

Single molecule fluorescence spectroscopy has been employed to resolve the conformational heterogeneity, hybridization kinetics and study mutational effects on the c-MYC promoter G-quadruplex.     

Triarylpyridines: a versatile small molecule scaffold for G-quadruplex recognition

The triarylpyridines are potent G-quadruplex ligands that are highly discriminating against duplex DNA and show promising selectivity between intramolecular quadruplexes.     

Copper‐Free Sonogashira Coupling of Acid Chlorides with Terminal Alkynes in the Presence of a Reusable Palladium Catalyst: An Improved Synthesis of 3‐Iodochromenones (=3‐Iodo‐4H‐1‐benzopyran‐4‐ones)

Pd/C is used as an efficient catalyst for the copper‐free Sonogashira coupling of acid chlorides and terminal alkynes to afford ynones in high yields (Tables 1 and 3). Cyclization of (2‐methoxyaryl)‐substituted ynones induced by I₂/ammonium cerium(IV) nitrate (CAN) at room temperature gave 3‐iodochromenones (=3‐iodo‐4H‐1‐benzopyran‐4‐ones) in excellent yield (Table 4).     

Stability and Hopf bifurcation of a Nonlinear oscillator with multiple time-delays

This paper examines dynamical behavior of a nonlinear oscillator which models a quarter-car forced by the road profile. The effect of multiple time delays is studied in detail. The focus is on the influence of delay in the system. This naturally gives rise to a delay differential equation (DDE) model of the system. The domain where the control is efficient in reducing the amplitude of vibration is found by the harmonic balance method. Technical stability within definite time and asymptotic stability is derived for selected gain control parameters. The control gain parameters are chosen according to technical and asymptotic stability. The energy analysis is a combination of Lyapunov’s function and the averaging technique, and is used to analyze the Hopf bifurcation.     

Reagent‐Based DOS: Developing a Diastereoselective Methodology to Access Spirocyclic‐ and Fused Heterocyclic Ring Systems

Herein, we report a diversity‐oriented‐synthesis (DOS) approach for the synthesis of biologically relevant molecular scaffolds. Our methodology enables the facile synthesis of fused N‐heterocycles, spirooxoindolones, tetrahydroquinolines, and fused N‐heterocycles. The two‐step sequence starts with a chiral‐bicyclic‐lactam‐directed enolate‐addition/substitution step. This step is followed by a ring‐closure onto the built‐in scaffold electrophile, thereby leading to stereoselective carbocycle‐ and spirocycle‐formation. We used in silico tools to calibrate our compounds with respect to chemical diversity and selected drug‐like properties. We evaluated the biological significance of our scaffolds by screening them in two cancer cell‐lines. In summary, our DOS methodology affords new, diverse scaffolds, thereby resulting in compounds that may have significance in medicinal chemistry.     

Topological charge dependent propagation of optical vortices under quadratic phase transformation

We make optical vortices of different topological charge and diffract them through a quadratic phase mask using the same spatial light modulator. This phase mask shows the diffraction in which the positive diffracted order has different dynamics than the negative diffracted order. The diffraction pattern and its orientation depend on the charge of the vortex as well as its sign. The experimental results are verified with exact analytical results.     

Asymmetric Synthesis of (R)-Fluoxetine: A Practical Approach Using Recyclable and in-situ Generated Oxazaborolidine Catalyst

A practical route for the synthesis of (R)-fluoxetine•HCl (ee＝96%) in 56% overall yield was described. The key intermediate (R)-3-chloro-1-phenyl-1-propanol was obtained by the asymmetric reduction of prochiral 3-chloropropiophenone using in-situ generated oxazaborolidine catalyst derived from (S)-α,α-diphenylprolinol. The chiral procatalyst (S)-α,α-diphenylprolinol was recovered quantitatively and recycled. An improved practical synthesis of (S)-α,α-diphenylprolinol was also discussed.