The synthesis of a series of thiacyclophanes and optically active binaphthol-based chiral thiacyclophanes is reported with XRD structure. Two diastereomeric tetrathiacyclophanes are designed and synthesized. The two diastereomers are evidenced by crystal structure; the single-crystal X-ray studies reveal that one of the isomers possesses an inherent property of self-assembling into a vertical stack of tunnel-like structures. 相似文献
Herbarumin I a phytotoxic 10-membered lactone has been synthesized from d-(?)-isoascorbic acid in 12 steps with an overall yield of 16.8%. The methodology involved in generating the stereogenic center at C-8 is a Sharpless asymmetric epoxidation, as well 1,2-asymmetric induction followed by macrolactonization via RCM. 相似文献
SnCl2·2H2O mediated efficient synthesis of pyrano[2,3-b]pyridines was achieved by the Friedländer reaction of 2-amino-3-cyano-4H-pyrans with cyclopentanone/cyclohexanone under solvent-free condition. 相似文献
Three‐component coupling reactions of an alkyne, an enone, and a diboron reagent provide access to highly substituted alkenyl boronates in good to excellent yields (see scheme). The coupling is highly regio‐ and stereoselective, and the products are amenable to further functional‐group transformations. R1,R2=H, alkyl, aryl, CO2Me; R3=alkyl, Ph; R4,R5=H, alkyl.
Two novel cyclohexane-1,2-diamino and N,N dimethyl amino-propyl substituted hypocrellin B derivatives, abbreviated as CHA2HB and DMAHB, respectively were synthesized. These derivatives exhibited enhanced absorption in phototherapeutic window. Photodynamic action of these derivatives, investigated using optical and electron spin resonance methods, depended on both Type I and Type II mechanisms. Gel electrophoresis indicated 1O2/O2(.-) mediated DNA damage. CHA2HB displayed 20 fold increase in light dependent cytotoxicity on colon cancer cell line (HCT 116) than the well-known hypocrellin B (HB). The light induced, LD(50) values for CHA2HB and DMAHB were found to be 0.1 microM and 1.5 microM, respectively. The singlet oxygen generating efficiency followed the order HB>CHA(2)HB>DMAHB. But, the enhanced red absorption as well as the hydrophilicity renders the CHA2HB a better photodynamic therapeutic agent. 相似文献
We report two fluorophores with open coordination sites for specific sensing of Ni(2+) and Cu(2+) ions via a simple synthetic route. The fluorescence activity was completely quenched on coordination of the metal ions with the phenanthroline ring present in the fluorophore as is clearly evident from the photophysical studies. 相似文献
Spectra of γ-ray Doppler shifts for positron annihilation in benzene and its fluoro-derivatives are simulated using low energy plane wave
positron (LEPWP) approximation. The results are compared with available measurements. It is found that the Doppler shifts
in these larger aromatic compounds are dominated by the contributions of the valence electrons and that the LEPWP model overestimates
the measurements by approximately 30%, in agreement with previous findings in noble gases and small molecules. It is further
revealed that the halogen atoms not only switch the sign of the charges on carbon atoms that they bond to, but that they also
polarize other C-H bonds in the molecule leading to a redistribution of the molecular electrostatic potentials. As a result,
it is likely that the halogen atoms contribute more significantly to the annihilation process. The present study also suggests
that, while the Doppler shifts are sensitive to the number of valence electrons in the molecules, they are less sensitive
to the chemical structures of isomers that have the same numbers and type of atoms and, hence, the same numbers of electrons.
Further investigation of this effect is warranted. 相似文献
A new and efficient metal-free approach toward the synthesis of phenols via an aerobic hydroxylation of arylboronic acids by using a novel quaternary ammonium hydroxide g-C3N4 catalyst has been described. The functionalized quaternary ammonium hydroxide (g-C3N4-OH) has been prepared from graphitic carbon nitride (g-C3N4) scaffold by converting the residual –NH2 and –NH groups to quaternary methyl ammonium iodide by performing a methylation reaction with methyl iodide followed by ion-exchange with 0.1 N KOH or anion exchange resin Amberlyst A26 (OH- form) by post-synthetic modification. The resultant g-C3N4-OH was characterized by XRD, FTIR, field-emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), N2 adsorption/desorption isotherms, and acid–base titration. Tested as solid-base catalysts, the g-C3N4-OH showed excellent catalytic activity in the aerobic hydroxylation reaction by converting a variety of arylboronic acids to the corresponding phenols in high yields. More importantly, the g-C3N4-OH solid-base has been successfully reused four times with the minor loss of initial catalytic activity (10.5%). 相似文献
Bis-chromanones and their derivatives were prepared via alkylation, saponification and cyclization reactions under conventional conditions. These bis-chromanones displayed bathochromic shifts and also showed potential biological activity against human pathogenic bacteria. 相似文献