Chul Min Park

Enantioselective iodocyclization and mercuriocyclization of γ-hydroxy- cis -alkenes

Asymmetric iodocyclization and mercuriocyclization of γ-hydroxy-cis-alkenes have been established. The iodocyclization has been attained with 1.2 equiv of iodine in the presence of the catalyst system prepared from 0.3 equiv of (R,R)-salen−Co(II) complex and 0.75 equiv of NCS to produce 2-substituted tetrahydrofurans with up to 90% ee. The mercuriocyclization has been achieved using 1.2 equiv of Hg(II) complexed with 4-(2-naphthyl)bisoxazoline (1:1 complex) in the presence of 5 equiv of K2CO3 and 10 equiv of MeOH to procure 2-substituted tetrahydrofurans with up to 95 % ee.

A Nonpeptidic Reverse-Turn Scaffold Stabilized by Urea-Based Dual Intramolecular Hydrogen Bonding

A novel nonpeptidic reverse-turn scaffold containing urea fragments that are connected by a conformationally constrained D-prolyl-cis-1,2-diaminocyclohexane (D-Pro-DACH) linker is reported. The scaffold adopts a well-defined reverse-turn conformation that is stabilized by dual intramolecular hydrogen bonding in both solution and solid states.

GNA/aegPNA Chimera Loaded with RNA Binding Preference

Peptide nucleic acid (PNA) is an oligonucleotide mimic, in which the sugar-phosphate backbone is replaced by a pseudo-peptide skeleton, composed of N-(2-aminoethyl)-glycine (aeg) units carrying nucleobases via methylene carbonyl linkages (Figure 1 a). Owing to its neutral amide backbone, aegPNA has outstanding chemical and enzymatic stability as well as high binding affinities to DNA and RNA, which gives it great potential for development as an antisense agent or diagnostic tools in a chip-based assay.