Pinacol Rearrangement of 3,4‐Dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

3‐Alkyl/aryl‐3‐hydroxyquinoline‐2,4‐diones were reduced with NaBH₄ to give cis‐3‐alkyl/aryl‐3,4‐dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H₂SO₄, resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1H)‐ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3‐hydroxyquinolin‐2(1H)‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopy, as well as mass spectrometry.     

Reaction of Some 2‐Quinolone Derivatives with Phosphoryl Chloride: Synthesis of Novel Phosphoric Acid Esters of 4‐Hydroxy‐2‐quinolone

3‐Chloroquinoline‐2,4‐diones do not react with phosphoryl chloride, however, 2,4‐dichloroquinolines and/or 4‐chloroquinolin‐2‐ones are formed in the presence of N,N‐dimethylaniline. Along with these compounds, small quantities of novel dihydrogen phosphates of 4‐hydroxyquinolin‐2‐ones were isolated. We outline a simple procedure that allows for the preparation of these compounds in moderate to good yields. All compounds were characterized by ¹H and ¹³C NMR, IR, EI‐MS, and ESI‐MS spectroscopy, and in select cases by ³¹P NMR spectroscopy.     

Benzofurazane as a New Redox Label for Electrochemical Detection of DNA: Towards Multipotential Redox Coding of DNA Bases

Benzofurazane has been attached to nucleosides and dNTPs, either directly or through an acetylene linker, as a new redox label for electrochemical analysis of nucleotide sequences. Primer extension incorporation of the benzofurazane‐modified dNTPs by polymerases has been developed for the construction of labeled oligonucleotide probes. In combination with nitrophenyl and aminophenyl labels, we have successfully developed a three‐potential coding of DNA bases and have explored the relevant electrochemical potentials. The combination of benzofurazane and nitrophenyl reducible labels has proved to be excellent for ratiometric analysis of nucleotide sequences and is suitable for bioanalytical applications.     

Three‐Dimensional Architectures Incorporating Stereoregular Donor–Acceptor Stacks

We report the synthesis of two [2]catenane‐containing struts that are composed of a tetracationic cyclophane (TC⁴⁺) encircling a 1,5‐dioxynaphthalene (DNP)‐based crown ether, which bears two terphenylene arms. The TC⁴⁺ rings comprise either 1) two bipyridinium (BIPY²⁺) units or 2) a BIPY²⁺ and a diazapyrenium (DAP²⁺) unit. These degenerate and nondegenerate catenanes were reacted in the presence of Cu(NO₃)₂?2.5 H₂O to yield Cu‐paddlewheel‐based MOF‐1050 and MOF‐1051. The solid‐state structures of these MOFs reveal that the metal clusters serve to join the heptaphenylene struts into grid‐like 2D networks. These 2D sheets are then held together by infinite donor–acceptor stacks involving the [2]catenanes to produce interpenetrated 3D architectures. As a consequence of the planar chirality associated with both the DNP and hydroquinone (HQ) units present in the crown ether, each catenane can exist as four stereoisomers. In the case of the nondegenerate (bistable) catenane, the situation is further complicated by the presence of translational isomers. Upon crystallization, however, only two of the four possible stereoisomers—namely, the enantiomeric RR and SS forms—are observed in the crystals. An additional element of co‐conformational selectivity is present in MOF‐1051 as a consequence of the substitution of one of the BIPY²⁺ units by a DAP²⁺ unit: only the translational isomer in which the DAP²⁺ unit is encircled by the crown ether is observed. The overall topologies of MOF‐1050 and MOF‐1051, and the selective formation of stereoisomers and translational isomers during the kinetically driven crystallization, provide evidence that weak noncovalent bonding interactions play a significant role in the assembly of these extended (super)structures.     

High‐ and low‐temperature phases in isostructural 4‐chloro‐3‐nitroaniline and 4‐iodo‐3‐nitroaniline

The structures of 4‐chloro‐3‐nitroaniline, C₆H₅ClN₂O₂, (I), and 4‐iodo‐3‐nitroaniline, C₆H₅IN₂O₂, (II), are isomorphs and both undergo continuous (second order) phase transitions at 237 and 200 K, respectively. The structures, as well as their phase transitions, have been studied by single‐crystal X‐ray diffraction, Raman spectroscopy and difference scanning calorimetry experiments. Both high‐temperature phases (293 K) show disorder of the nitro substituents, which are inclined towards the benzene‐ring planes at two different orientations. In the low‐temperature phases (120 K), both inclination angles are well maintained, while the disorder is removed. Concomitantly, the b axis doubles with respect to the room‐temperature cell. Each of the low‐temperature phases of (I) and (II) contains two pairs of independent molecules, where the molecules in each pair are related by noncrystallographic inversion centres. The molecules within each pair have the same absolute value of the inclination angle. The Flack parameter of the low‐temperature phases is very close to 0.5, indicating inversion twinning. This can be envisaged as stacking faults in the low‐temperature phases. It seems that competition between the primary amine–nitro N—H...O hydrogen bonds which form three‐centred hydrogen bonds is the reason for the disorder of the nitro groups, as well as for the phase transition in both (I) and (II). The backbones of the structures are formed by N—H...N hydrogen bonding of moderate strength which results in the graph‐set motif C(3). This graph‐set motif forms a zigzag chain parallel to the monoclinic b axis and is maintained in both the high‐ and the low‐temperature structures. The primary amine groups are pyramidal, with similar geometric values in all four determinations. The high‐temperature phase of (II) has been described previously [Garden et al. (2004). Acta Cryst. C 60 , o328–o330].     

Comparison of Transcriptomic Profiles of MiaPaCa-2 Pancreatic Cancer Cells Treated with Different Statins

Statins have been widely used for the treatment of hypercholesterolemia due to their ability to inhibit HMG-CoA reductase, the rate-limiting enzyme of de novo cholesterol synthesis, via the so-called mevalonate pathway. However, their inhibitory action also causes depletion of downstream intermediates of the pathway, resulting in the pleiotropic effects of statins, including the beneficial impact in the treatment of cancer. In our study, we compared the effect of all eight existing statins on the expression of genes, the products of which are implicated in cancer inhibition and suggested the molecular mechanisms of their action in epigenetic and posttranslational regulation, and in cell-cycle arrest, death, migration, or invasion of the cancer cells.     

Coulomb analogy for non-Hermitian degeneracies near quantum phase transitions

Degeneracies near the real axis in a complex-extended parameter space of a Hermitian Hamiltonian are studied. We present a method to measure distributions of such degeneracies on the Riemann sheet of a selected level and apply it in classification of quantum phase transitions. The degeneracies are shown to behave similarly as complex zeros of a partition function.     

Crystal and Molecular Structures of Mononuclear Coordinated Copper(I) Complexes with Thio-triazole and Thio-triazine based Schiff base Ligands

Reaction of 4-amino-5-methyl-1,2,4-triazol-3(2H)-thione (AMTT) and 4-amino-6-methyl-3-thio-3,4-dihydro-1,2,4-triazin-5(2H)-one (AMTTO) with 2-hydroxybenzaldehyde led to the synthesis of corresponding Schiff base ligands [(Z)-4-((2-hydroxybenzylidene)amino)-3-methyl-1H-1,2,4-triazole-5(4H)-thione ( L1 ) and (Z)-4-((2-hydroxybenzylidene)amino)-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one ( L2 )]. Treatment of synthesized Schiff base ligands with CuCl provided the complexes [Cu(L1)₃Cl] ( 1 ) and [Cu(L2)₂Cl] ( 2 ). Synthesized complexes were characterized by elemental analyses, IR spectroscopy and X-ray diffraction studies. Complex 1 consists of a metal ion coordinated with one chloride ion and three Schiff base ligands via sulfur atoms in a distorted tetrahedral environment, whereas 2 consists of a metal ion coordinated with one chloride ion and two sulfur atoms from two different Schiff base ligands in a trigonal planar arrangement. Crystal data for 1 at –153 °C revealed an orthorhombic space group Fdd2, a = 34.8088(7), b = 33.8156(8), c = 11.6142(2) Å, Z = 16, R₁ = 0.0357; for 2 at –178 °C the symmetry was triclinic, space group P1 , a = 7.27520(10), b = 15.4620(2), c = 23.7985(4) Å, α = 72.1964(13), β = 86.5208(12), γ = 89.8597(11)°, Z = 4, R₁ = 0.0359.