Keun Ho Chun

A short synthesis of bicyclic sugar pyrimidine nucleosides from C-glycosides

Abstract The C -glycosides were prepared from dichloroketene cycloaddition reaction to glycals and converted to bicyclic sugar nucleosides in good yields.

A ONE-POT CONVENIENT PROCEDURE FOR THE SYNTHESIS OF C-GLYCOSIDE VIA CYCLOADDITION OF DICHLOROKETENE TO GLYCAL AND DECHLORINATION OF THE CYCLOADDUCT

ABSTRACT A convenient procedure for the synthesis of C-glycoside was developed via cycloaddition of dichloroketene, generated in situ, to glycal and dechlorination of the cycloadduct using zinc and acetic acid.

Photoinduced one pot transformation of 2-phenyl-4-ethylidene-5(4H)-oxazolone and allylic alcohols to γ, δ-unsaturated N-benzoyl amides

Abstract Photolysis of 2-Phenyl-4-ethylidene-5(4H)-oxazolones in the presence of allylic alcohols resulted in a novel one-pot transformation to γ,δ-unsaturated N-benzoyl amides via decarbonylation, nucleophilic addition of allylic alcohols, photoinduced hydrogen transfer and the Claisen rearrangement.

Discovery of ursolic acid prodrug (NX-201): Pharmacokinetics and in vivo antitumor effects in PANC-1 pancreatic cancer

The aim of our study was to develop ursolic acid (UA) prodrugs in order to overcome UAs weakness, which has an extremely low bioavailability. UA-medoxomil (NX-201), one of our UA prodrugs, showed an improved bioavailability about 200times better than UA in rodent model. According to in vivo test performed with PANC-1 xenograft SCID mouse model, tumor growth rate decreased dose-dependently and 100mg/kg dose of NX-201 had an anticancer effect comparable to gemcitabine. Most of all the combination of NX-201 (50mg/kg, po, daily) and gemcitabine (40mg/kg, iv, 2timesperweek) even reduced tumor size after three weeks.

Synthesis of 2′-Azidoethyl Trisaccharide, α-D-Gal-(1→2)-6d-α-D-Altro-Hepp-(1→3)-(β-D-GlcNAc, an o-antigenic repeating unit of C.jejuni 0:23 and 0:36

A trisaccharide, the O-antigenic repeating unit ofC. jejuni serotype 0:23 and 0:36, was synthesized as a 2′-azidoethyl glycoside by block addition of perbenzylated thiogalactoside donors to α-altroHepp-(1→3)-GlcNPhth disaccharide acceptor in presence of IDCP promoter. The αlinkedaltro heptopyranoside moiety in the glycosyl acceptor was effectively prepared bySwern oxidation of α-mannohepp-(1→3)-GlcNPhth disaccharide followed by mild reduction with NaCNBH3.