Stereoselective Synthesis of the Non‐Lactonic Portion of (Z)‐Cryptofolione and Approaches towards Its Conversion to (Z)‐Cryptofolione

The stereoselective synthesis of the non‐lactonic part of the natural G₂ checkpoint inhibitor, (Z)‐cryptofolione, has been accomplished. Butane‐1,4‐diol was used as the starting material, and the stereogenic centers were generated through L ‐proline‐catalyzed α‐aminoxylation and Maruoka asymmetric allylation. We attempted to convert this non‐lactonic moiety to (Z)‐cryptofolione via olefin cross‐metathesis reaction, but by this approach another naturally occurring lactonic compound, goniothalamin, was obtained.     

Synthesis of Aib‐ and Phe(2Me)‐Containing Cyclopentapeptides

Some recently described pentapeptides containing the α,α‐disubstituted α‐amino acids Aib and Phe(2Me) have been cyclized in DMF solution using diphenyl phosphorazidate (DPPA), O‐(1H‐benzotriazol‐1‐yl)‐N,N,N′,N′‐tetamethyluronium tetrafluoroborate/1‐hydroxybenzotriazole (TBTU/HOBt), and diethyl phosphorocyanidate (DEPC), respectively, to give the corresponding cyclopentapeptides in fair‐to‐good yields. In the case of peptides with L ‐amino acids, and (R)‐ and (S)‐Phe(2Me), the yields differed significantly in favor of the L /(R) combination. The conformations in the crystals of cyclo(Gly‐Aib‐(R,S)‐Phe(2Me)‐Aib‐Gly) and cyclo(Gly‐(R)‐Phe(2Me)‐Pro‐Aib‐Gly) have been determined by X‐ray crystallography, leading to quite different results. In the latter case, the conformation in solution has been elucidated by NMR studies.     

First Stereoselective Synthesis of the Cytotoxic Polyketide (4R)‐1‐(3,5‐Dihydroxyphenyl)‐4‐hydroxypentan‐2‐one

The first stereoselective synthesis of the cytotoxic polyketide (4R)‐1‐(3,5‐dihydroxyphenyl)‐4‐hydroxypentan‐2‐one ( 1 ) was achieved from readily available propylene oxide and 3,5‐dimethoxybenzyl alcohol. The synthesis involves Jacobsen's hydrolytic kinetic resolution (HKR) and Grignard reaction as key steps.     

New Cu(I) Coordination Complexes Based on Tetrathiafulvalene Substituted Triazol‐pyridine Ligand: Synthesis,Properties and Theoretical Studies

Two Cu(I) complexes based on the thioethyl‐bridged triazol‐pyridine ligand with tetrathiafulvalene unit (TTF‐TzPy, L ), [Cu(I)(Binap)(L)]BF₄ ( 5 , Binap=2,2’‐bis(diphenylphosphino)‐1,1’‐binaphthyl) and [Cu(I)(Xantphos)(L)]BF₄ ( 6 , Xantphos=9,9‐dimethyl‐4,5‐bis(diphenylphosphino)‐xanthene), have been synthesized. All new compounds are characterized by elemental analyses, ¹H NMR and mass spectroscopies. The complex 5 has been determined by X‐ray structure analyses which shows that the central copper (I) ion assumes distorted tetrahedral geometry. The photophysical, computational and electrochemical properties of L and 5 ‐ 6 have been investigated. The most representative molecular orbital energy‐level diagrams and the spin‐allowed singlet? singlet electronic transitions of the three compounds have been calculated with density functional theory (DFT) and time‐dependent DFT (TD‐DFT). The luminescence bands of Cu(I) complexes 5 ‐ 6 have been assigned as mixed intraligand and metal‐to‐ligand charge transfer ³(MLCT+π→π^*) transitions through analysis of the photophysical properties and DFT calculations. The electrochemical studies reveal that 5 ‐ 6 undergo reversible TTF/TTF^+?/TTF²⁺ redox processes and one irreversible Cu⁺→Cu²⁺ oxidation process.     

Thermodynamic properties,detonation characterisation and free radical of N-acetyl-3,3-dinitroazetidine

N-acetyl-3,3-dinitroazetidine (ADNAZ) is an important precursor for synthesizing new multinitroazetidine energetic compounds. Its thermal behaviour was studied under a non-isothermal condition by DSC and TG/DTG methods, the results show that there are one melting process and one endothermic decomposition process. The specific molar heat capacity (C_p,m) of ADNAZ was determined by a continuous C_p mode of micro-calorimeter and theoretical calculation, and the C_p,m of ADNAZ was 240.37 J · K⁻¹ · mol⁻¹ at T = 298.15 K. The detonation velocity (D) and detonation pressure (P) of ADNAZ were estimated using the nitrogen equivalent equation according to the experimental density, the value of D and P are (6685.83 ± 3.12) m · s⁻¹ and (18.36 ± 0.02) GPa, respectively. The free radical signals of ADNAZ were detected by electron spin resonance (ESR) technique, which is used to estimate its sensitivity.     

(Vapour + liquid) equilibrium data for the {1,1-difluoroethane (R152a) + 1,1,1,3,3-pentafluoropropane (R245fa)} system at temperatures from (323.150 to 353.150) K

In this paper, (vapour + liquid) equilibrium (VLE) for the {1,1-difluoroethane (R152a) + 1,1,1,3,3-pentafluoropropane (R245fa)} system was determined by a static-analytical method at T = (323.150 to 353.150) K. Values of the VLE were correlated by the Peng–Robison equation of state (PR EoS) using two different models, the van der Waals (vdWs) mixing rule and the Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient model. The correlated results show good agreement with the experimental values. For the two models, the maximum average absolute deviations of the vapour phase mole fraction are 0.0034 and 0.0035, respectively.     

Interaction of RuIII(EDTA) with cellular thiols and O2: biological implications thereof

Reaction of [Ru^III(EDTA)(CyS)]^2? (edta^4? = ethylenediaminetetraacetate; CySH = cysteine) with molecular oxygen (O₂) has been studied as a function of pH (4.0–8.0) and cysteine concentration (0.2–2.0 mM) at room temperature (25 °C). Biological activities of the [Ru(EDTA)]/CySH/O₂ system pertaining to cleavage of supercoiled plasmid DNA to its nicked open circular form has been explored in this work. Results are discussed in regard to the reaction of the ruthenium(III)-complex with molecular oxygen) and a working mechanism is proposed for the biological activities of the ruthenium(III)-complex in the presence of O₂.     

Copper(I)-1,1,1-tris(diphenylphosphinomethyl)ethane complexes with different coordination modes tuned by auxiliary ligands and their spectroscopic properties

Three mono-, bi- and tetranuclear copper(I) complexes, [Cu(phen)(triphos-O)]BF₄ (1) (phen = 1,10-phenanthroline, triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane), [Cu₂(bipy)(triphos)₂](BF₄)₂ (2) (bipy = 4,4′-bipyridine), and [Cu₄(MeOC^N^N)₄(triphos)₂(bipy)](BF₄)₄ (3) (MeOC^N^N = 6-(4-methoxyphenyl)-2,2′-bipyridine), have been synthesized and characterized by NMR spectroscopy, electrospray ionization, and matrix-assisted laser desorption ionization time-of-flight mass spectrometries, elemental analysis, and X-ray crystal analysis. The crystal structure investigation revealed the copper ions of the complexes have pseudo-tetrahedral coordination geometry. The electronic absorption spectra of 1, 2, and 3 contain low-energy bands at 350–500 and 400–650 nm, which are assigned to d(Cu) → π*(phen or bipy) and a mixture of d(Cu) → π*(MeOC^N^N) and d(Cu) → π*(bipy) transitions, respectively. Complex 2 displays a strong, long-lived solid-state emission with a maximum at 555 nm and lifetime of 13.6 μs at room temperature. Photoinduced electron-transfer properties of 2 and 3 involving nanosecond time-resolved absorption spectroscopy and electron spin resonance techniques were studied.     

Two Uranyl Complexes with Pyromellitic Acid. A Heterometallic Complex with U=O–CuII Interaction

Two uranyl complexes based on pyromellitic acid were hydrothermally synthesized, and their X‐ray single‐crystal diffraction structures were determined. Complex [UO₂(Hbtec)]^–(Himd)⁺ · H₂O ( 1 ) (H₄btec = pyromellitic acid, imd = imidazole), is an ionic complex, which shows a typical (4, 4) topological structure in the space. A heterometallic complex, UO₂Cu(btec)(phen) ( 2 ) (phen = 1,10‐phenanthroline) results from the reaction of uranyl nitrate and copper(II) bromide with pyromellitic acid. The structure of complex 2 revealed that the chains of UO₇ and CuO₃N₂ units were connected to each other through the carboxyl groups and U=O–Cu interactions to create a two‐dimensional framework.