Photochemical pinacol rearrangements of unsymmetrical diols

The photochemical pinacol reaction of a series of nonsymmetrical 9-fluorenyl-substituted vic-diols was investigated and compared with their acid-catalyzed thermal reaction. Unlike the thermal reaction, the radiation-induced processes involve only fluorenyl cations, as is reflected in differences of product distribution between the two reactions. From the product studies, substituent migratory aptitudes are reversed in the photochemical process, suggesting that kinetic control takes place under neutral conditions unlike the acid-catalyzed thermal reactions. The presence of fluorenyl cation intermediates and their lifetimes were established by laser flash spectroscopy studies.     

Atomistic Simulation Study of Cu0.327Ni0.673 Alloys: from Solid Solution to Phase Segregation

We present a combined Monte‐Carlo/molecular dynamics study of a Cu_0.327Ni_0.673 alloy system. On the basis of nearest‐neighbor coordination number analyses atomic clustering and phase segregation is explored. Along this line, free energy profiles are calculated and separated into entropic and energetic contributions. The competition of both terms was found in accordance to the experimental phase diagrams (phase separation of the solid solution below about 600 Kelvin). Two independent simulation runs were performed. At 1000 Kelvin the observed configurations correspond to solid solutions exhibiting a weak tendency to cluster atoms of identical species. At room temperature the energetic favoring of atomic separation is clearly dominant and leads to the formation of Ni‐rich and Cu‐rich domains. The latter are separated by interfacial regions whose width ranges from 0.5 to 1 nanometers.     

Three New Iron(II) Thiocyanato Coordination Polymers Based on 4,4′‐Bipyridine as Ligand and the Influence of Methanol on Their Structures

Reaction of iron(II) thiocyanate with 4,4‐bipyridine (bipy) in methanol leads to the formation of three new solvates of different composition depending on the reaction conditions: At room temperature two new ligand‐rich 1:2 (1:2 = ratio between metal and N‐donor ligand) polymorphic forms [Fe(NCS)₂(bipy)₂ · 2MeOH]_n ( 1I ) and [Fe(NCS)₂(bipy)(MeOH)₂ · (bipy)]_n ( 1II ) are obtained, whereas solvothermal conditions leads to the formation of the new ligand‐deficient 1:1 compound [{Fe(NCS)₂(bipy)(MeOH)}₂]_n ( 2 ). All crystal structures were determined by X‐ray single crystal structure analysis. In the crystal structure of modification 1I the metal atoms are coordinated by four bridging bipy ligands, which connect them into layers. The methanol molecules occupy voids in the structure. Compared to 1I in modification 1II the crystal structure contains of linear Fe–bipy–Fe chains, which are further connected by hydrogen bonds between coordinating MeOH and noncoordinated bipy ligands into layers. The ligand‐deficient 1:1 compound 2 shows a completely different coordination topology with linear Fe–bipy–Fe chains, which are connected by coordinating methanol molecules into double‐chains. In all compounds the thiocyanato anions are terminal N‐bonded to the metal atoms. Investigation of the thermal behavior of compound 1I shows a two‐step decomposition, in which ligand‐deficient intermediates are formed. Magnetic measurements on 1I reveal Curie–Weiss paramagnetism with increasing antiferromagnetic interactions on cooling.     

Selective reagent ionisation‐time of flight‐mass spectrometry: a rapid technology for the novel analysis of blends of new psychoactive substances

In this study we demonstrate the potential of selective reagent ionisation‐time of flight‐mass spectrometry for the rapid and selective identification of a popular new psychoactive substance blend called ‘synthacaine’, a mixture that is supposed to imitate the sensory and intoxicating effects of cocaine. Reactions with H₃O⁺ result in protonated parent molecules which can be tentatively assigned to benzocaine and methiopropamine. However, by comparing the product ion branching ratios obtained at two reduced electric field values (90 and 170 Td) for two reagent ions (H₃O⁺ and NO⁺) to those of the pure chemicals, we show that identification is possible with a much higher level of confidence then when relying solely on the m/z of protonated parent molecules. A rapid and highly selective analytical identification of the constituents of a recreational drug is particularly crucial to medical personnel for the prompt medical treatment of overdoses, toxic effects or allergic reactions. Copyright © 2015 John Wiley & Sons, Ltd.     

Selective glycoprotein detection through covalent templating and allosteric click-imprinting

Many glycoproteins are intimately linked to the onset and progression of numerous heritable or acquired diseases of humans, including cancer. Indeed the recognition of specific glycoproteins remains a significant challenge in analytical method and diagnostic development. Herein, a hierarchical bottom-up route exploiting reversible covalent interactions with boronic acids and so-called click chemistry for the fabrication of glycoprotein selective surfaces that surmount current antibody constraints is described. The self-assembled and imprinted surfaces, containing specific glycoprotein molecular recognition nanocavities, confer high binding affinities, nanomolar sensitivity, exceptional glycoprotein specificity and selectivity with as high as 30 fold selectivity for prostate specific antigen (PSA) over other glycoproteins. This synthetic, robust and highly selective recognition platform can be used in complex biological media and be recycled multiple times with no performance decrement.     

Approaches to phenazine-derived N-isosteres of anthracyclinones

1-Hydroxyphenazine 5,10-dioxide showed antitumor properties against mouse leukemia P388. It also participated in biochemical mechanisms of quinoid antitumor agents, as indicated by inhibition of radiolabeled DNA-RNA precursors in cultured leukemia L1210 cells and by stimulation of oxygen consumption in mammalian microsomes. This suggests that the isosteric di-N-oxide system may be a biologically active substitute for 1,4-quinone, and that di-N-oxides of tetrahydrobenzo[b]phenazines can be explored as anthracyclinone N-isosteres. As potential synthetic intermediates, 7,8,9,10-tetrahydro-6,11-dihydroxybenzo[b]-phenazines have been prepared by 1) Diels-Alder addition of phenazine-1,4-quinone and 1-methoxy-3-(trimethylsilyloxy)-1,3-butadiene to give isolable but labile adducts and 2) condensation of 6,7-diamino-1,2,3,4-tetrahydro-2-hydroxy-5,8-dimethoxy-2-naphthoic acid with 3-methoxy-1,2-quinone. Attempts at N-oxidation gave instead oxidation of the 6,11-hydroquinone ring to quinone, regardless of hydroxyl protection. Despite previous literature indications, we have been unable to synthesize the 1,4-dihydroxyphenazine 5,10-dioxide system. We conclude that this hydroxyl substitution pattern (1,4) in an adjacent ring must be avoided in the redesign of anthracyclinone isosteres that have di N-oxide in place of quinone.