Wing Lai Chan

Enantioselective alkynylation of aromatic aldehydes catalyzed by new chiral amino alcohol-based ligands

Abstract A series of binaphthyl-derived amino alcohols were synthesized and used as catalytic ligands in the asymmetric alkynylation of aromatic aldehydes in the presence of a dialkylzinc reagent. The alkynylation of a variety of aromatic aldehydes gave the corresponding chiral propargylic alcohols in 61–93% e.e.

Effective activation of chiral BINOL/Ti(OiPr)4 catalyst with phenolic additives for the enantioselective alkynylation of aldehydes

The activation of chiral titanium(IV) complexes with achiral activators, e.g. phenol, is found to provide higher levels of enantioselectivity than those attained with an enantiopure catalyst in the alkynylations of both aromatic and aliphatic aldehydes.

Copper-catalyzed enantioselective conjugate addition of triethylaluminum to 2-cyclopentenone

Abstract Bidentate phosphites were prepared starting from BINOL, H 8 -BINOL or 3,3′, 5,5′-tetra- tert- butyl-2,2′-biphenol. Utilization of these ligands in the copper-catalyzed enantioselective conjugate addition of triethylaluminum to 2-cyclopentenone afforded 3-ethylcyclopentanone in up to 94.0% ee.

Titanium-catalyzed enantioselective alkynylation of aldehydes

A simple and practical method to make chiral propargylic alcohols has been developed: in the presence of a titanium alkoxide catalyst prepared in situ from titanium tetraisopropoxide and (R)-H8-binaphthol, a variety of aromatic aldehydes were converted to the corresponding chiral propargylic alcohols with very good enantioselectivities (up to 96.2% e.e.) and yields.

Suspension of Silver Oxide Nanoparticles in Chitosan Solution and its Antibacterial Activity in Cotton Fabrics

New stable silver oxide suspension in chitosan solution was prepared from a mixture of silver nitrate and chitosan in dilute acetic acid as precursor, in which the complex interactions between silver ion and chitosan was also investigated through various instrumentation method seriously. The suspension was charactized through laser scan, infrared ray spectroscopy (IR), ultraviolet-visible spectroscopy (UV-vis) and X-ray diffraction (XRD), which indicated that the interactions between silver and chitosan in its precursor were destroyed partially. The measurements of the nanoparticles through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) disclosed the spherical profiles of these silver oxide nanoparticles of 10-20nm in average. Cotton fabrics treated by this emulsion were entitled remarkable antibacterial activity against S aureus and E. coli at pH 5 and 7 with sightless color effect and good washing fastness.

Chiral recognition of amino acid esters by zinc porphyrin derivatives

Three novel chiral zinc porphyrins (4a–4c) with protected chiral amino acid substituents as chiral sources were synthesized. Their chiral recognition of amino acid methyl esters was investigated using UV-vis spectrophotometric titration. Some enantioselectivities obtained are higher than that of the known system, and the highest achieved in our study is 21.54 using host 4a with PheOCH3 as guest. We also show that higher enantioselectivity can be obtained at lower temperature. Circular dichroism spectra of chiral porphyrin derivatives binding to enantiomers of guests show great shape and intensity differences. Molecular modeling was performed to understand chiral recognition on a molecular level, and the results are in good agreement with the experimental data.

Carboxamidophenylsydnone : a mesoionic mesogen for liquid crystals

Abstract A new class of liquid crystals based on carboxamidophenylsydnone was synthesized by a simple reaction between 3-(4-aminophenyl)sydnone and appropriate aliphatic carboxylic acids in the presence of SiCl 4 .

BIOACTIVE METABOLITES FROM MARINE MICROORGANISMS

Abstract Diverse arrays of new bioactive secondary metabolites have been isolated from marine microorganisms; and the number of publications in this area has greatly increased in recent years. In this review, the emphasis is placed on new compounds with antitumor, enzyme inhibitors, antivirus, and other bioactive metabolites from fungi, bacteria, actinomycetes, and cyanobacteria reported between 2000 and 2005. Supply is a major limitation in the development of marine bioproducts, and the methods for supplying these products are important. So in this review, the secondary major point is placed on the chemical synthetic studies. References of 390 structures and 263 citations are overall presented in this review.

2-Hexyl­idene-3-methyl­succinic acid

School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, People’s Republic of China, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510080, People’s Republic of China, Department of Biology and Chemistry, The Hong Kong Polytechnic University, Hong Kong, People’s Republic of China, and Open Laboratory of Chirotechnology of the Institute of, Molecular Technology for Drug Discovery and Synthesis, The Hong Kong Polytechnic University, Hong Kong, People’s Republic of China