Synthesis of New Conjugates of Modified Podophyllotoxin and Stavudine

To find podophyllotoxin compounds with superior bioactivitiy and less toxicity, a series of novel conjugates of ring‐A‐modified 4‐epipodophyllotoxin and stavudine with amino acids as spacers were synthesized, i.e., the N‐[(2′,3′‐didehydro‐3′‐deoxythymidin‐5′‐O‐yl)carbonyl]‐substituted L ‐amino acid rel‐(3aR,4S,9R,9aR)‐1,3,3a,4,9,9a‐hexahydro‐6,7‐dimethoxy‐1‐oxo‐9‐(3,4,5‐trimethoxyphenyl)naphtho[2,3‐c]furan‐4‐yl esters 8a – 8f .     

DFT/TDDFT study on the electronic structures and optoelectronic properties of several red-emitting osmium(II) complexes with different P^P ancillary ligands

The ground and excited state geometries of several red-emitting phosphors (N^N)(2)Os(P^P) [where N^N = 5-(1-isoquinolyl)-1,2,4-triazoles, P^P = bis(dimethylphosphino)methylene(dmpm) (1); P^P = cis-1,2-bis-(dimethylphosphino)ethene(dmpe) (2); P^P = 1,2-bis(dimethylphosphino)benzene(dmpb) (3); P^P = 1,2-bis(dimethylphosphino)naphthalene(dmpn) (4); P^P = 1,2-bis(dimethylphosphino)-4-cyano-benzene(dmpcb) (5)] have been investigated by using the density functional theory (DFT) methods. The calculated results indicate that, for the studied complexes, the electron-transporting performance is better than the hole-transporting performance. The alteration of cis-P^P ancillary ligands with different conjugation lengths and substituents has an impact on the optoelectronic properties of these complexes, especially the electron-withdrawing group -CN in 5. The calculated energy gaps are nearly the same for complexes 1 to 4 (3.34 eV), while for 5, the HOMO and LUMO energies are lowered and the energy gap increases (3.42 eV). The absorption of 1 is red shifted, while that of 5 is blue shifted compared with the absorptions of 2, 3, and 4, which have similar absorptions. Complexes 2, 3, and 4 have almost identical emission wavelength 699 nm, while 1 (715 nm) and 5 (735 nm) are red shifted. The calculated electron affinities and reorganization energies indicate that complex 5 is the easiest for electron injection and has the best electron-transporting performance.     

Patterned polyelectrolyte multilayer: surface modification for enhancing selective adsorption

This paper describes the use of surface chemical modification to enhance the difference of the surface charge on a patterned polyelectrolyte multilayer, which can be used for selectively adsorbing functional materials. We fabricated a patterned multilayer by combining the layer-by-layer self-assembly technique and photolithography and taking advantage of the different solubility of polyelectrolyte multilayers of diazo resins (DAR)/poly(acrylic acid) before and after UV irradiation. This patterned surface can be used as a matrix for selective adsorption of small molecular dyes, such as Methylene Blue. However the difference in surface charge on the patterned surface was not enough when we used it to selectively adsorb polystyrene (PS) nanoparticles using electrostatic force as the driving force. Therefore, we modified the patterned surface by interfacial chemistry. After modification, the patterned polyelectrolyte multilayer can be used as a good matrix for selective adsorption of PS nanoparticles with both positive and negative charges.     

Unique Thia‐Baeyer–Villiger‐Type Oxidation of Dibenzothiophene Sulfoxides Derivatives

The present research has demonstrated that selective C?S bond cleavages of dibenzothiophene and its derivatives are feasible by thia‐Baeyer–Villiger type oxidation, i. e. the oxygen insertion process within a sulfoxide‐carbon linkage, in the presence of porphyrin iron (III) and by ultraviolet irradiation originating from sunlight, high pressure Hg‐lamp or residentially germicidal ultraviolet lamp under very mild conditions. This reaction with tert‐butylhydroperoxide at 30.0 °C leads to dibenzo[1,2]oxathiin‐6‐oxide ( PBS ) in 83.2 % isolated yield or its hydrated products, 2‐(2‐hydroxyphenyl)‐benzenesulfinic derivatives ( HPBS ) in near 100 % yield based HPLC data. PBS and HPBS are a type of biological products detected on the C?S bond cleavage step through various oxidative biodesulfurization ( OBDS ) pathways, and are useful synthetic intermediates and fine chemicals. These observations may contribute on understanding delicately molecular aspect of OBDS in the photosynthesis system, expanding the C‐S cleavage chemistry of S‐heterocyclic compounds and approaching toward biomemic desulfurization with respect to converting sulfur contaminants to chemically beneficial blocks as needed and performing under the ambient conditions.     

Pestalustaines A and B,unprecedented sesquiterpene and coumarin derivatives from endophytic fungus Pestalotiopsis adusta

Pestalustaines A (1) and B (2), one unique sesquiterpene possessing an unusual 5/6/7-fused tricyclic ring system and one unprecedented coumarin derivative bearing 6/6/5/5-fused tetracyclic ring system, were isolated from the plant-derived Pestalotiopsis adusta. Their structures with absolute configurations were established by extensive NMR analysis, X-ray crystallography, and CD spectra associated with TD-DFT calculation. Hypothetical biosynthetic pathways for compounds 1 and 2 are proposed. Compounds 1 and 2 showed weak to moderate cytotoxic activities against three human tumor cell lines HeLa, HCT116, and A549, whose IC₅₀ values were ranged from 21.01 to 55.43?μM.     

Syntheses,Crystal Structures and Properties of Organic–Inorganic Hybrid Compounds of 4,4′-Bipyridine–Decorated Ni/Cu-Substituted Molybdophosphates

Organic–inorganic hybrid compounds of transition metal mono-substituted molybdophosphates, (H₂bipy)₂[PNi(Hbipy)Mo₁₁O₃₉]·4H₂O (1), (H₂bipy)_1.5[HPCu(Hbipy)Mo₁₁O₃₉]·4H₂O (2) (bipy = 4,4′-bipyridine), were synthesized hydrothermally and characterized by elemental analysis, IR spectroscopy, TGA, fluorescent spectroscopy, powder and single crystal X-ray diffraction methods. In 1 and 2 the transition metal atom (Ni and Cu) occupies one site of twelve molybdenum atoms of Keggin anion and combines a monoprotonated bipyridine molecular cation, Hbipy⁺, forming a 4,4′-bipyridine–decorated M-substituted molybdophosphate anion (M = Ni and Cu). In 1 two anions form a dimer through hydrogen bonds, in 2 the anions form a chain through hydrogen bonds. The dimers or the chains, H₂bipy²⁺ cations and lattice water molecules are connected by hydrogen bonds, giving supramolecular compounds. The two kinds of bipy molecules, coordinated and uncoordinated, in 1 and 2 give two emission peaks in their photoluminescent spectra.     

Two new compounds from the fruit of Ailanthus altissima

A new phenolic derivative, 4-hydroxyphenol-1-O-[6-O-(E)-feruloyl-β-d-glucopyranosyl]-(1→6)-β-d-glucopyranoside (1), and a new terpenylated coumarin, named altissimacoumarin H (2) were identified from the fruit of Ailanthus altissima (Mill.) Swingle (Simaroubaceae), together with ten known compounds (3–12), including two coumarins and eight phenylpropanoids. Their structures were determined on the basis of chemical method and spectroscopic data. Antiviral effect against Tobacco mosaic virus (TMV) of all the compounds obtained were evaluated using leaf-disc method.     

Biomimetic Chiral Pyridoxal and Pyridoxamine Catalysts

Vitamin B₆ serves as universal co‐enzymes in biological systems. However, its catalytic power has not been applied into the area of asymmetric catalysis. Based on the core structure of vitamin B₆, we have developed several types of pyridoxal and pyridoxamine catalysts with different structural skeletons and different electronic properties. With these pyridoxals and pyridoxamines as catalysts, we have realized biomimetic asymmetric transamination of α‐keto acids and biomimetic asymmetric Mannich reaction of glycinate, respectively, to give various chiral α‐amino acids and α,β‐diamino acids in good yields with excellent diastero‐ and/or enantioselectivities. Both of the reactions have perfectly mimicked the corresponding biological transformations.     

Post‐Treatment of CH3NH3PbI3/PbI2 Composite Films with Methylamine to Realize High‐Performance Photoconductor Devices

Organometallic halide perovskites have attracted great research interest as light‐active materials for use in optoelectronics. Here, we report a high‐performance photoconductor based on a methylammonium lead iodide (MAPbI₃) film that was prepared from a methylamine‐treated MAPbI₃/PbI₂ perovskite film. An ultrahigh responsivity of 3.6 A W^?1 and detectivity of 5.4×10¹² Jones were obtained for the film under 0.5 mW cm^?2 white‐light illumination. In addition, under 420 nm light irradiation, the film exhibited its highest responsivity and detectivity of 30 A W^?1 and 2.4×10¹⁴ Jones, respectively. The excellent photo‐response performance results from the improved electronic quality and suppressed nonradiative recombination channels of the treated perovskite thin film.     

Inside Cover: From Reactivity and Regioselectivity to Stereoselectivity: An Odyssey of Designing PIP Amine and Related Directing Groups for C—H Activation (Chin. J. Chem. 7/2019)

The inside cover picture shows the journey of developing PIP amine directing group for C—H activation, from controlling the reactivity and diastereoselectivity to enantioselectivity. In the presence of Pd or base metal catalysts, PIP amine enabled the activation of inert C—H bonds to form diverse C—C and C—heteroatom bonds. Its tuneable structure has triggered the design of chiral auxiliaries for diastereoselective C—H activation. More recently, enantioselective activation of unbiased methylene C—H bonds has been achieved by cooperative effects between PIP amine and axial chiral ligands. More details are discussed in the article by Shi et al. on page 647–656.