Optical Resolution of the Water-Soluble Ti-4(embonate)(6) Cages for Enantioselective Recognition of Chiral Drugs

Synergetic optical resolution and chiral amplification of tetrahedral Ti4L6 cages by enantiopure coordination cations have been realized in this work. Anionic Delta Delta Delta Delta-[Ti4L6] and Lambda Lambda Lambda Lambda-[Ti4L6] cages (L = embonate) have been completely resolved by enantiopure Lambda-[Mn(1R,2R-DCH)(3)] and Delta-[Mn(1S,2S-DCH)(3)] cations, respectively. Accordingly, two homochiral compounds (PTC-108(Delta) and PTC-108(Lambda)) with three-dimensional supramolecular architectures were formed, containing larger diamondoid cages. Such an unusual resolution process clearly shows the stepwise transfer of homochirality from an enantiopure molecule to a resolved hydrogen-bonding aggregation and a final homochiral framework. Moreover, the separated homochiral Ti4L6 cage presents enantioselective recognition toward chiral organic and pharmaceutical molecules. This work opens a novel resolution-dependent homochiral framework construction approach, and it also takes the homochiral tetrahedral Ti4L6 cages with high solubility and stability into promising enantioselective application.