@misc{oai:ir.soken.ac.jp:00000313,
 author = {曹, 紅花 and ソウ, コウカ and CAO, Honghua},
 month = {2016-02-17, 2016-02-17},
 note = {Biomacromolecules such as protein and nucleic acid are excellent functional molecules, which play crutial roles in the vital functions in biological system in an accurate and well-controlled manner. Owing to recent developments in organic synthesis and biotechnology, it has become feasible to chemically modify these molecular structures at the molecular level.    
　　An alternative approach she has used for the reconstruction of DNA is the direct modification of nucleobases by incorporating metal-chelating nucleobases into DNA strands. In this artificial DNA, hydrogen-bonded base pairing is replaced by metal-induced base pairing, thereby creating a novel hybridization motif in double-stranded DNA (Chart 1). 

(Chart 1 was abbreviated.)

   She has synthesized an artificial β-C-nucleoside 6 which have a catechol group as a nucleobase. This novel nucleoside was synthesized from a 2'-deoxyribose derivartive 1 and О-protected catechol 2 via Friedel-Crafts coupling reaction to selectively afford the desired product β-C-nucleoside 4 in 36% yield. The following two-step deprotection procedures afforded the target β-C-nucleoside 6 (Scheme 1).

(Scheme 1 was abbreviated.)

   Catechol-bearing β-C-nucleoside 6 was treated with half amount of trimethyl borate and triethylamine in DMSO-d<SUB>6</SUB>, at room temperature to obtain 2:1 complex 7 between nucleosides and boron (III) (Scheme 2). 

(Scheme 2 was abbreviated.)

The isotopically resolved ESI-TOF mass spectrum of this solution in the negative mode provided clear evidence for the 2:1 complexation between 6 and boron ion. The singnal at m/z 459.15 [7-Et<SUB>3</SUB>NH<SUP>+</SUP>]<SUP>-</SUP> gave excellent agreement between the experimental and theoretical isotopic distributions indicating the boron-assisted dimerization of 6. 500 MHz <SUP>1</SUP>H NMR resonances from aromatic protons of the complex 7 in DMSO-d<SUB>6</SUB> were upfield-shifted from those of the nucleoside 6, and the signals for hydroxy protons on the catechol moiety disappeared upon complexation, whereas those for the ribose moity still remained. These results indicate that phenoxy groups coordinated to the boron (III) center, in the deprotonated form, that is to say a boron (III) ion promoted base pairing of 6. Although there are two possible diastereomeric structures for the complex 7, they only observed one set of proton signals for the complex 7 in the spectrum. 
   She then tried to incorporate a catechol-type β-C-nucleoside as a "chelator- nucleoside" building block into a DNA strand by means of a phosphotriester or a phosphoramidite approach. She synthesized phosphoramidite type 10 and phosphotriester-type 12 and 13, starting from compound 9 (Scheme 3), which can be used to introduce the catechol-type nucleoside into oligo- DNA. 
   
(Scheme 3 was abbreviated.)

   This work demonstrates a novel base pairing mode assisted by borate formation, which would provide an alternative DNA base pair in addition to other metal-assisted base pairs that have been developed in our group so far. This novel base pair at specific site of oligo-DNA would contribute to the development of new structural and functionalized super-biomolecules., application/pdf, 総研大甲第490号},
 title = {配位結合により塩基対を形成する人工カテコール型ヌクレオシドの合成と機能化},
 year = {}
}