Kyoo-Hyun Chung

Antimicrobial activity of phenol and benzoic acid derivatives

Vinyl monomers with phenol and benzoic acid as pendant groups were synthesized, and their antimicrobial activities were examined on equal weight basis using the halo zone test. For both bacteria and fungi, the halo zone diameter decreased in the order of p-hydroxyphenyl acrylate (M2) > allyl p-hydroxyphenyl acetate (M1) p-2-propenoxyphenol (M3). Polymerization of the monomers decreased their antimicrobial activity significantly, but the order of the halo zone diameter for the polymers was the same as that of the corresponding monomers. Glassy polymers exhibited low antimicrobial activity when compounded with low molecular weight antimicrobial agents due to the extremely slow diffusion. Antimicrobial polymers could find a successful application such as coating on glassy polymers, in spite of the lower antimicrobial activity compared to the respective monomers.

Antifungal effect of carbendazim supported on poly(ethylene‐co‐vinyl alcohol) and epoxy resin

Ethylene-vinyl alcohol copolymers (EVOH) were prepared by the conventional saponification of poly(ethylene-co-vinyl acetate) using a solution of potassium hydroxide in ethanol. An organic fungicide, consisting of a 2-benzimidazole carbamoyl (CBZ) group supported on EVOH (EVOH-CBZ), was prepared by the transesterification reaction of methyl 2-benzimidazole cabamate (carbendazim) with EVOH. The antifungal activity of the synthesized polymers was examined by the halo zone test against Aspergillus fumigatus and Penicillium pinophilum. The synthesized EVOH-CBZ complex showed a strong antifungal activity. The bound CBZ units were susceptible to hydrolysis. CBZ bonded to an epoxy resin precursor, diglycidyl ether of bisphenol A (DGEBA-CBZ), retained its antifungal activity, which was somewhat weaker in comparison with that of EVOH-CBZ. When the DGEBA-CBZ complex was crosslinked by isophoronediamine, the antifungal activity disappeared almost completely, indicating that it is necessary for the CBZ units to release from their polymer supports to have the antifungal effects.

Synthesis and binding affinities of fluoroalkylated raloxifenes

Three fluoroalkylated derivatives (1-3) of the selective estrogen receptor modulator (SERM), raloxifene, have been synthesized. The key step in the synthesis is the C-C bond formation of benzo[b]thiophene and a substituted phenyl group (ring C) using a Stille reaction. The in vitro binding affinities of the substituted raloxifenes 1-3 are 45, 60, 89%, respectively, relative to the affinity of estradiol, which is higher than the affinity of raloxifene itself (25%). When labeled with the positron-emitting radionuclide, these compounds might be useful as PET imaging agents for estrogen receptor-positive breast tumors.

Practical neutral aromatic nitration with nitrogen dioxide in the presence of heterogeneous catalysts under moderate oxygen pressure

A practical neutral aromatic nitration process using nitrogen dioxide in the presence of FeCl3 · 6H2O under 40–100 psig of oxygen was developed, and nitration of several aromatic compounds, including the deactivated nitrobenzene, was performed in a successful manner. The correlation of reaction rate with equivalents nitrogen dioxide, oxygen pressure, amount of catalyst and temperature was investigated through the nitration of benzene. Following the optimization of reaction conditions, the nitration of benzene was scaled up to 476 mol. Furthermore, inorganic solid catalysts with pore size over 5 Å and surface area over 100 m2/g were applied to newly developed neutral nitration.

Metal Chelations in Asymmetric Diels-Alder Reaction

Diels-Alder cycloadditions of chiral dieno-philes with cyclopentadiene proceed with diastereofacialselectivity, giving either endo-R or endo-S compounds as amajor component, depending on Lewis acids used.In the reaction, the inverse asymmetric induction has beenobserved by the use of either monovalent Lewis acids ordivalent Lewis acids. The reaction of the acrylate of ( S)-ethyllactate with cyclopentadiene proceeded with 86% endo-Sselectivity in the presence of TiCl

Synthesis and binding affinities of 2β-(3-iodoallyloxycarbonyl)-3β-(4-substituted-aryl)tropane analogues as ligands for the dopamine transporter studies

Abstract Tropane analogues from cocaine, which is known to be one of the most reinforcing and addictive compounds, were designed, synthesized, and characterized for inhibition of presynaptic uptake of dopamine (DA) in brain. Eight new derivatives of 3β-aryl-2β-(3-iodoallyloxycarbonyl)tropanes were synthesized and tested for their potential abilities to displace [ 3 H]2β-carbomethoxy-3β-(4-fluorophenyl)tropane (WIN 35,428) binding to the rat striatal membranes.