Hee-Kwon Kim

Aerobic oxidative esterification and thioesterification of aldehydes using dibromoisocyanuric acid under mild conditions: no metal catalysts required

A practical direct method for the direct preparation of esters and thioesters from aldehydes is described. Esters and thioesters were synthesized by oxidative esterification and thioesterification via in situ generated acyl bromide intermediates, which were used to react with various alcohols and thiols. The esterification and thioesterification were readily performed in the presence of dibromoisocyanuric acid in dichloromethane, without any metal catalysts and under mild conditions. By using this reaction protocol, various esters and thioesters were prepared in high yields. This effective method offers a promising approach for the facile esterification and thioesterification of aldehydes.

Synthesis of novel multivalent fluorescent inhibitors with high affinity to prostate cancer and their biological evaluation

Prostate-specific membrane antigen (PSMA) is an important biological target for therapy and diagnosis of prostate cancer. In this study, novel multivalent PSMA inhibitors with glutamate-urea-lysine structures were designed to improve inhibition characteristics. Precursors of the novel inhibitors were prepared from glutamic acid with di-tert-butyl ester. A near-infrared molecular dye, sulfo-Cy5.5, was introduced into the precursors to generate the final PSMA fluorescent inhibitors, compounds 12-14, to visualize prostate cancer. Biological behaviors of the inhibitors were evaluated using in vitro inhibition assays, in vivo fluorescent imaging, and ex vivo biodistribution assays. Ki values from inhibition studies indicated that dimeric inhibitor 13 with a glutamine linker showed approximately 3-fold more inhibitory activity than monomeric inhibitor 12. According to other biological studies using a mouse model of prostate cancer, dimeric inhibitor compounds 13 and 14 had higher tumor accumulation than the monomer. However, glutamine-based dimeric inhibitor 13 showed lower liver uptake than dimeric inhibitor 14, which had a benzene structure. Thus, these studies suggest that glutamine-based dimeric inhibitor 13 can be a promising optical inhibitor of prostate cancer.

Facile and Efficient Synthesis of [18F]Fluoromisonidazole Using Novel 2-Nitroimidazole Derivatives

[18F]Fluoromisonidazole ([18F]FMISO) is a hypoxia imaging marker utilized in positron emission tomography. Novel FMISO precursors were prepared from a commercially available material, and several reaction factors that affect synthesis of [18F]FMISO were examined to achieve a higher fluorination yield. [18F]FMISO was obtained from radiosynthesis, followed by the hydrolysis of protecting groups with HCl. New 2-nitroimidazole precursor showed a higher [18F]fluorination and a higher synthetic yield. This result provided alternative guidelines for the preparation of hypoxia imaging marker.