Design of a fused triazolyl 2-quinolinone unnatural nucleoside via tandem CuAAC-Ullmann coupling reaction and study of photophysical property

This report presents the design and synthesis of a novel fused triazolyl 2-quinolinone (FTQuon) nucleoside as a new generation of angularly widened unnatural nucleobase surrogate with two possible H-bonding faces-one H-bond acceptor and another donor. The synthesis via a tandem CuAAC-Ullmann coupling, the study of photophysical properties and theoretical calculation in the context of DNA are the main contents of this report. The newly designed nucleoside shows interesting photphysical property with slight blue shifted solvatochromicity. It also shows pH sensitive emission. All the theoretical DNA duplexes containing the FTQuon show right?handed B-form helicity as revealed from a molecular dynamics simulation using Schrodinger Macromodel. A theoretical (DFT) study indicates a good stabilizing property of FTQuon via pairing with natural pyrimidine bases. It also shows good interaction property with BSA protein signalled via a switch on fluorescence response.     

Electrospray ionization mass spectrometry of tributyltin(IV) complexes and their larvicidal activity on mosquito larvae: crystal and molecular structure of polymeric (Bu3Sn[O2CC6H4{NN(C6H3‐4‐OH(C(H)NC6H4OCH3‐4))}‐o])n

A series of tributyltin(IV) complexes of 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls have been investigated by electrospray mass spectrometry (ESI‐MS) and tandem mass spectrometry (MSⁿ) techniques. The assignments are facilitated by agreement between observed and calculated isotopic patterns and MSⁿ studies. Single‐crystal X‐ray crystallography of (Bu₃Sn[O₂CC₆H₄{N?N(C₆H₃‐4‐OH(C(H)?NC₆H₄OCH₃‐4))}‐o])_n reveals a polymeric structure. Toxicity studies of the tributyltin(IV) complexes of the 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls on the second larval instar of the Aedes aegypti and Anopheles stephensi mosquito larvae are also reported. The LC₅₀ values indicate that the complexes are effective larvicides, which range from a low of 0.36 ppm to a high of 0.69 ppm against the Ae. aegypti larvae and between 0.82 and 1.17 ppm against the An. stephensi larvae. Copyright © 2005 John Wiley & Sons, Ltd.     

Studies directed towards the synthesis of botcinolides: synthesis of the nonalactone ring of 2-epibotcinolide

Synthesis of the polyoxygenated nonalactone ring of 2-epibotcinolide was achieved using a highly stereoselective aldol reaction of the titanium enolate from a lactate-derived chiral ketone, a stereoselective dihydroxylation and a Yamaguchi macrolactonization reaction.     

Total Synthesis of Panaginsene

The total synthesis of panaginsene has been accomplished in 11 linear steps starting from methyl 3,3-dimethyl-5-oxocyclopent-1-ene-1-carboxylate. The key steps are a Sharpless asymmetric epoxidation and Ti(III)-mediated reductive epoxide opening-radical cyclization to construct the chiral quaternary carbon stereocenter followed by a very challenging HWE olefination reaction on an 1,3-keto aldehyde and a late stage McMurry olefination using low valent titanium to construct the highly constrained angular tetrasubstituted olefin in a five-membered ring.     

A delayed prey–predator model with Crowley–Martin‐type functional response including prey refuge

In this paper, we have studied a prey–predator model living in a habitat that divided into two regions: an unreserved region and a reserved (refuge) region. The migration between these two regions is allowed. The interaction between unreserved prey and predator is Crowley–Martin‐type functional response. The local and global stability of the system is discussed. Further, the system is extended to incorporate the effect of time delay. Then the dynamical behavior of the system is analyzed, taking delay as a bifurcation parameter. The direction of Hopf bifurcation and the stability of the bifurcated periodic solution are determined with the help of normal form theory and centre manifold theorem. We have also discussed the influence of prey refuge on densities of prey and predator species. The analytical results are supplemented with numerical simulations. Copyright © 2017 John Wiley & Sons, Ltd.     

Stereoselective construction of quaternary chiral centers using Ti(III)-mediated opening of 2,3-epoxy alcohols: studies directed toward the synthesis of penifulvins

A trisubstituted α,β-unsaturated ester moiety was suitably placed in a molecule also bearing an epoxy alcohol moiety at its other end to intramolecularly trap the intermediate radical, which was formed when the molecule was treated with Cp₂Ti(III)Cl to regio- and stereoselectively open its epoxy ring, giving rise to a quaternary chiral center. The method was subsequently used in an attempt to construct the bicyclic core framework of potent insecticides penifulvins.     

A Practical,Flexible and Highly Stereocontrolled Approach to Densely Functionalized Diquinanes

The Diels-Alder adduct 1 has been tailored into the difficultly accessible angularly substituted diquinanes 6a-d in high overall yield.     

A Convenient Method for the Synthesis Of Tröger's Base Analogues

Para substituted anilines have been converted to Tröger's base analogues by refluxing with a mixture of methylal and methanesulfonic acid.