| Summary: | 碩士 === 中山醫學大學 === 應用化學系碩士班 === 99 === Optical active β-cyclodextrin (β-CD) often serves as the chiral selector for the separation of enantiomers. However, because of its higher C7 symmetry and non-ionic peripherals, β-CD only shows moderate chiral discrimination efficiency toward limited racemic pools. In the present research, mono- and bis-poly (amido amine) (PAMAM) dendrons-substituted β-CD derivatives were successfully synthesized to reduce the intrinsic symmetry of unmodified β-CD and to yield multiple positive charges on the primary face. G1 and G2 NH2-terminated PAMAM dendrons were prepared through divergent pathway using propargylamine as the focal point, and then copper(I)-catalyzed Huisgen [2 + 3] dipolar cycloaddition reaction (click reaction) successfully conjugated the azide-functionalized β-CD and thus-prepared PAMAM dendrons. Mono and bis-adduct were obtained by the conjugation of mono-azido-functionalized β-CD with the G2 PAMAM dendron and by the coupling of regioselective 6A,6D-bis(azido)-substituted β-CD with two G1 PAMAM dendrons via click reaction, respectively. After dialysis and lyophilization to give final highly water-soluble β-CD/PAMAM complexes, the protonation level of internal tertiary amines and peripheral primary amines was adjusted by pH titration. The 1H NMR analysis clearly indicated that the primary amines were completely protonated but the tertiary amine remains in neutral state at neutral pH, which allows us to control the charge density of these β-CD derivatives by using suitable pH buffer. We also anticipate the mono and bis-PAMAM-substituted β-CD derivatives, bearing lower C1 and C2 symmetry and multiple positive charges, could be the considerable chiral selectors for the separation of anionic enatiomeric pairs.
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