Yoshizawa Michito, Tamura Masazumi, Fujita Makoto
Department of Applied Chemistry, School of Engineering, University of Tokyo, and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Science. 2006 Apr 14;312(5771):251-4. doi: 10.1126/science.1124985.
Self-assembled, hollow molecular structures are appealing as synthetic hosts for mediating chemical reactions. However, product binding has inhibited catalytic turnover in such systems, and selectivity has rarely approached the levels observed in more structurally elaborate natural enzymes. We found that an aqueous organopalladium cage induces highly unusual regioselectivity in the Diels-Alder coupling of anthracene and phthalimide guests, promoting reaction at a terminal rather than central anthracene ring. Moreover, a similar bowl-shaped host attains efficient catalytic turnover in coupling the same substrates (although with the conventional regiochemistry), most likely because the product geometry inhibits the aromatic stacking interactions that attract the planar reagents to the host.
自组装的中空分子结构作为介导化学反应的合成主体很有吸引力。然而，产物结合抑制了此类体系中的催化周转，并且选择性很少能达到在结构更复杂的天然酶中所观察到的水平。我们发现，一种有机钯水相笼在蒽和邻苯二甲酰亚胺客体的狄尔斯-阿尔德偶联反应中诱导出高度异常的区域选择性，促进反应发生在蒽的末端环而非中心环上。此外，一种类似碗状的主体在偶联相同底物时实现了高效的催化周转（尽管具有传统的区域化学性质），最有可能的原因是产物的几何形状抑制了吸引平面试剂至主体的芳香堆积相互作用。
