Prediction of Chromatographic Retention of Pyrazine and Alkylpyrazines in RP-LC

Retention prediction models for a group of pyrazines chromatographed under reversed-phase mode were developed using multiple linear regression (MLR) and artificial neural networks (ANNs). Using MLR, the retention of the analytes were satisfactorily described by a two-predictor model based on the logarithm of the partition coefficient of the analytes (log P) and the percentage of the organic modifier in the mobile phase (ACN or MeOH). ANN prediction models were also derived using the predictors derived from MLR as inputs and log k as outputs. The best network architecture was found to be 2-2-1 for both ACN and MeOH data sets. The optimized ANNs showed better predictive properties than the MLR models especially for the ACN data set. In the case of the MeOH data set, the MLR and ANN models have comparable predictive performance.     

Efficient Oxidation of 1,2‐Diols into α‐Hydroxyketones Catalyzed by Organotin Compounds

Get selective! A selective oxidation of 1,2‐diols to α‐hydroxyketones catalyzed by organotin compounds has been developed (see scheme). Invaluable chemo‐ and stereoselectivity were found in the reaction. The catalytic system has been achieved by electrochemical and chemical oxidation.

     

A Novel Double‐Network Hydrogel Induces Spontaneous Articular Cartilage Regeneration in vivo in a Large Osteochondral Defect

We have developed a novel method to induce spontaneous hyaline cartilage regeneration in vivo for a large osteochondral defect by implanting a plug made from a double‐network hydrogel composed of poly(2‐acrylamido‐2‐methylpropanesulfonic acid) and poly(N,N′‐dimethylacrylamide) at the bottom of the defect, leaving the cavity vacant. In cells regenerated in the treated defect, type‐2 collagen, Aggrican, and SOX9 mRNAs were highly expressed and the regenerated matrix was rich in proteoglycan and type‐2 collagen at 4 weeks. This fact gave a significant modification to the commonly established concept that hyaline cartilage tissue cannot regenerate in vivo. This study prompted an innovative strategy in the field of joint surgery to repair an osteochondral defect using an advanced, high‐function hydrogel.

     

Synthesis and characterization of silver(I) adducts supported solely by 1,3,5-triazapentadienyl ligands or by triazapentadienyl and other N-donors

Halogenated 1,3,5-triazapentadienyl ligands [N{(C(3)F(7))C(C(6)F(5))N}(2)](-), [N{(CF(3))C(C(6)F(5))N}(2)](-) and [N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)](-), alone or in combination with other N-donors like CH(3)CN, CH(3)(CH(2))(2)CN, and N(C(2)H(5))(3), have been used in the stabilization of thermally stable, two-, three- or four-coordinate silver(i) adducts. X-Ray crystallographic analyses of {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag}(n), {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(NCCH(3))}(n), {[N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)]Ag(NCCH(3))}(n), {[N{(CF(3))C(C(6)F(5))N}(2)]Ag(NCCH(3))(2)}(n) and {[N{(C(3)F(7))C(C(6)F(5))N}(2)]Ag(NCC(3)H(7))}(n) revealed the presence of bridging 1,3,5-triazapentadienyl ligands bonded to silver through terminal nitrogen atoms. These adducts are polymeric in the solid state. [N{(C(3)F(7))C(2,6-Cl(2)C(6)H(3))N}(2)]AgN(C(2)H(5))(3) is monomeric and features a 1,3,5-triazapentadienyl ligand bonded to Ag(I) in a κ(1)-fashion via only one of the terminal nitrogen atoms. The solid state structure of [N{(C(3)F(7))C(C(6)F(5))N}(2)]H has also been reported and it forms polymeric chains via inter-molecular N-H···N hydrogen-bonding.     

Rh(I)-catalyzed formal [6 + 2] cycloaddition of 4-allenals with alkynes or alkenes in a tether

Rh(I)-catalyzed formal [6 + 2] cycloaddition of allenal 6 having an alkyne or alkene in a tether proceeded smoothly, giving 5-8- and 6-8-fused bicyclic ketone derivatives 7 in good to excellent yields. It was also found that cyclization of enantiomerically enriched (S)-6a (94% ee) gave cyclic ketone derivative (S)-7a in high yield with reasonable chirality transfer (86% ee). This result indicates that this cyclization proceeds through stereoselective formation of rhodacycle H' followed by insertion of a multiple bond.     

Synthesis and hybridization properties of 2'-O-methylated oligoribonucleotides incorporating 2'-O-naphthyluridines

2'-O-(1-Naphthyl)uridine and 2'-O-(2-naphthyl)uridine were synthesized by a microwave-mediated reaction of 2,2'-anhydrouridine with naphthols. Using the 3'-phosphoramidite building blocks, these 2'-O-aryluridine derivatives were incorporated into 2'-O-methylated oligoribonucleotides. Incorporation of five 2'-O-(2-naphthyl)uridines into a 2'-O-methylated RNA sense strand significantly increased the thermostability of the duplex with a 2'-O-methylated RNA antisense strand. Circular dichroism spectroscopy and molecular dynamic simulation of the duplexes formed between the modified RNAs and 2'-O-methyl RNAs suggested that there are π-π interactions between two neighboring naphthyl groups in a sequence of the five consecutively modified nucleosides.     

Chemical constituents of Lycoris albiflora and their cytotoxic activities

An alcoholic extract of Lycoris albiflora (Amaryllidaceae) showed potent cytotoxic activity against HL-60 cells with an IC50 value of 1.7 microg/mL. Phytochemical examination of the extract resulted in the isolation of 15 alkaloids, including two phenanthridine-type alkaloids (1, 2), one benzylphenethylamine-type alkaloid (3), two crinane-type alkaloids (4, 5), one pyrrolophenanthridine-type alkaloid (6), six lycorenan-type alkaloids (7-12), and three galanthamine-type alkaloids (13-15), together with three neolignans (16-18), two flavans (19, 20), and two acetophenone derivatives (21, 22). Compound 3 (hostasinine A) has not been isolated from Amaryllidaceae plants, and 1, 2, 4, 5, 7-9, 11, 12 and 14-22 are the first isolation and identification from L. albiflora. The phenanthridine-type alkaloids (1, 2), as well as the alkaloids (3-5), exhibited potent cytotoxic activities against not only HL-60 cells but also HSC-2 cells, thus leading to the conclusion that these alkaloids are mainly responsible for the cytotoxicity of the L. albiflora extract. Compound 1 (lycoricidinol), with the most potent cytotoxic activities, induced apoptosis in both HL-60 cells and HSC-2 cells. It is notable that 1 induced transient autophagy and morphological changes in mitochondria in the early stages of the apoptotic cell death process in HSC-2 cells.     

Interaction of Au(III) and Pt(IV) complex ions with Fe(II) ions as a scavenging and a reducing agent: a basic study on the recovery of Au and Pt by a chemical method

In order to develop a chemical technique for the recovery of gold (Au) and platinum (Pt) in the metallic state from spent catalysts, e.g., catalysts for environmental protection and automobile and petroleum catalysts, the coprecipitation behaviors of Au(III) and Pt(IV) complex ions with Fe(OH)(2) as a scavenging and reducing agent were investigated. The Au(III) complex ions were found to be stoichiometrically and rapidly reduced to metallic Au due to electron transfer in acidic aqueous solution prior to coprecipitation with Fe(OH)(2). Conversely, Pt(IV) complex ions were reduced only after coprecipitation with Fe(OH)(2) due to electron transfer through a Pt(IV)-O-Fe(II) bond on the solid Fe(OH)(2). Using this chemical technique, Au and Pt can be selectively and effectively recovered in the metallic state.     

Differential response of two Pinus spp. to avian nitrogen input as revealed by nitrogen isotope analysis for tree rings

Temporal variations in N concentration and δ(15)N value of annual tree rings (1 year of time resolution) of two Japanese Black Pine (Pinus thunbergii) and three Japanese Red Pine (Pinus densiflora) trees under current breeding activity of the Great Cormorant (Pharacrocorax carbo) and the Black-tailed Gull (Larus crassirostris), respectively, in central and northeastern Japan were studied. Both species from control sites where no avian input occurs show negative values (δ(15)N = around -4 ‰ to -2 ‰) which are common among higher plants growing under high rainfall regimes. The δ(15)N values of P. densiflora show uniformly positive values several years before and after the breeding event, indicating N translocation that moved the absorbed N of a given growth year to tree rings of the previous year while a clear historical value of soil N dynamics was kept intact in the annual rings of P. thunbergii. Long-term N trends inferred from tree rings must take into account tree species with limited translocation rates that can retain actual N annual acquisition.     

Periodic and chaotic oscillations of the electrochemical potential of p-Si in contact with an aqueous (CuSO4+HF) solution, caused by electroless Cu deposition

Periodic and chaotic oscillations were observed for the potential of p-type Si(111) immersed in an aqueous (HF+CuSO(4)) solution, accompanied by electroless Cu deposition on p-Si. They were, to our knowledge, the first examples of open-circuit potential oscillations observed for semiconductor electrodes. The oscillations appeared only when the Cu deposit formed a continuous porous film composed of mutually connected submicrometer-sized particles. Besides, the Si surface was kept flat within the size less than 50 nm even after the prolonged oscillation for a few hours, though the Si surface should be etched considerably with HF for this time. A plausible model is proposed for the periodic oscillation, in which interestingly coupling of autocatalytic shift in the flat-band potential of Si (U(fb)) caused by the change in the coverage of the Si oxide and the connection and disconnection of the Cu film with the Si surface plays the key role. The appearance of the chaotic oscillation is also explained by taking into account an oscillation-coupled change in the HF or Cu(2+) concentration near the Si surface.