Wong Chun-Ho, Chow Hak-Fun, Hui Sin-Kam, Sze Kong-Hung
Department of Chemistry and The Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Org Lett. 2006 Apr 27;8(9):1811-4. doi: 10.1021/ol0603716.
[reaction: see text] A new series of self-assembling G1-G3 dendronized dimers bearing oligoether dendrons and a dimeric 2-ureido-4-pyrimidinone (UPy) quadruple hydrogen-bonding core were prepared and characterized. It was found that the nonpolar microenvironment created by the dendrons preserved the UPy unit in its DDAA tautomeric form. As a result, the stabilities of the dimers were exceptionally strong for all three generations (K(dim) > 2 x 10(7) M(-)(1) in CDCl(3) at 25 degrees C). Furthermore, the steric size of the dendrons did not exhibit a significant effect on their dimerization behavior.
[反应：见正文] 制备并表征了一系列新的带有寡醚树枝状分子和二聚体2-脲基-4-嘧啶酮（UPy）四重氢键核心的自组装G1 - G3树枝状二聚体。研究发现，树枝状分子形成的非极性微环境使UPy单元保持其DDAA互变异构形式。因此，这三代二聚体的稳定性都异常高（在25℃的CDCl₃中，K(dim) > 2×10⁷ M⁻¹）。此外，树枝状分子的空间大小对其二聚行为没有显著影响。
