Unexpected regioselectivity observed in the bromination and epoxidation reactions of p-benzoquinone-fused norbornadiene: An experimental and computational study

The bromination reaction of p-benzoquinone-fused norbornadiene was studied at various temperatures (?78, ?50, 0, 25, and 77 °C). At room temperature, the double bonds of the p-benzoquinone units were mainly brominated. The double bond of the norbornene unit also underwent a bromination reaction in a yield of only 2%. However, the reaction at ?78 °C resulted in the formation of products derived from the attack of bromine on the norbornene double bond with higher charge density. In contrast to the bromination reaction, the epoxidation reaction of the same compound with m-chloroperbenzoic acid and dimethyldioxirane exclusively resulted in the formation of products derived from the addition to the double bond of norbornadiene. The regioselectivity observed was investigated and the results were supported by theoretical calculations.     

Non-Alkaloid Cholinesterase Inhibitory Compounds from Natural Sources

Alzheimer’s disease (AD) is a severe neurodegenerative disorder of different brain regions accompanied by distresses and affecting more than 25 million people in the world. This progressive brain deterioration affects the central nervous system and has negative impacts on a patient’s daily activities such as memory impairment. The most important challenge concerning AD is the development of new drugs for long-term treatment or prevention, with lesser side effects and greater efficiency as cholinesterases inhibitors and the ability to remove amyloid-beta(Aβ) deposits and other related AD neuropathologies. Natural sources provide promising alternatives to synthetic cholinesterase inhibitors and many have been reported for alkaloids while neglecting other classes with potential cholinesterase inhibition. This review summarizes information about the therapeutic potential of small natural molecules from medicinal herbs, belonging to terpenoids, coumarins, and phenolic compounds, and others, which have gained special attention due to their specific modes of action and their advantages of low toxicity and high efficiency in the treatment of AD. Some show superior drug-like features in comparison to synthetic cholinesterase inhibitors. We expect that the listed phytoconstituents in this review will serve as promising tools and chemical scaffolds for the discovery of new potent therapeutic leads for the amelioration and treatment of Alzheimer’s disease.     

Games,Critical Paths and Assignment Problems in Permutation Flow Shops and Cyclic Scheduling Flow Line Environments

In this paper we address the non-pre-emptive flow shop scheduling problem for makespan minimization in a new modelling framework. A lower bound generation scheme is developed by using appropriately defined linear assignment problems and, based on this new approach, a special class of permutation flow shop problems is identified. We present a game theoretic interpretation of our modelling approach which leads to an integer programming formulation of the scheduling problem. A new branch and bound scheme is developed based on these results. The major advantage of our modelling framework and branch-and- bound approach is that it can be easily extended to address a general class of cyclic scheduling problems for production flow lines with blocking. After a discussion of this extension, we report on computational experience that indicates the very satisfactory performance of the new optimal solution procedure for cyclic scheduling problems with finite capacity buffers.     

Extremely simple device for measuring 20-fs pulses

We demonstrate an extremely simple frequency-resolved optical-gating device (GRENOUILLE) capable of measuring pulses with spectra wider than 100 nm. Its nearly all-reflective geometry minimizes the material dispersion, allowing accurate measurement of pulses as short as 19 fs.     

Green-nano approach to nanostructured polypyrrole

Bulk quantities of polypyrrole nanofibers and nanospheres can be synthesized with a facile, one-step "green-nano" chemical oxidative polymerization approach, by simply using different reaction media.     

Synthesis, antihistaminic action and theoretical studies of (4-methoxybenzyl)(1,4,5,6-tetrahydropirimidin-2-yl)amine hydroiodide

In this study, (4-methoxybenzyl)(1,4,5,6-tetrahydropyrimidin-2-yl)amine hydroiodide (2) was synthesized by reaction of 2-methylmercapto-1,4,5,6-tetrahydropyrimidine hydroiodide (1) and 4-methoxybenzylamine. The synthesized compound was tested for its in vitro H1-antihistaminic activity on guinea pig trachea. A promising bronchorelaxant effect of 2 was observed in histamine-contracted guinea pig tracheal chain via H1 receptor antagonism. In addition, the molecular geometry and gauge including atomic orbital (GIAO) ¹H chemical shift values of the title compound in the ground state were calculated using the density functional method (DFT/UB3LYP) and Hartree–Fock (HF) approach using 6–311G+(d), 6–311G+(d,p), LANL2DZ, DGDZVP, and DGDZVP2 basis sets and compared with the experimental data. According to the experimental and theoretical results, HF/6–311G+(d) showed a better fit to experimental values in evaluating ¹H-nuclear magnetic resonance (NMR) chemical shift values. Theoretical studies supported our findings, revealing the N₁₂ atom as the most nucleophilic. In addition, other structures of the compound such as the aromatic ring and OCH₃ group increased this property.