Enantioselective addition of water to alkene is a challenge to organic chemists because of small size and low nucleophilicity of water a. In 2010, the first non-enzymatic catalytic asymmetric syn-hydration of enones using supramolecular assembled DNA hybrid catalysts was reported; providing β-hydroxy ketones up to 82% ee.1 Recently, we have established a systematic strategy for the development of DNA-based hybrid catalysts constructed with the counter base of metal complexes, neighboring bases in the active site, and disposition of the active site.2 In this study, we report enantioselective hydration of α, β-unsaturated ketones to β-hydroxy ketones by DNA-based hybrid catalysts containing intrastrand bipyridine ligand. We synthesized various DNA hybrid catalysts with 13-mer DNA oligonucleotides, 5'–d(GCATGGXCACGGT)–3'/5'–d(ACCGTGYCCATGC)–3', where X = a bipyridine ligand, Y = a non-binding steric moiety and obtained up to 89% enantioselectivity. Interestingly, we found that the present DNA-based hybrid catalyst afforded the opposite enantiomeric outcome compared with the previously reported supramolecular assembled Cu(II)−ligand/st−DNA catalyst. Further studies are underway to investigate temporal evolution of enantioselectivity and substrate scope.
1) A. J. Boersma, et al., Nat. Chem., 2010, 2, 991.
2) S. Park, et al., ACS. Catal., 2015, 5, 4708.
S. Park, H. Sugiyama, Angew. Chem. Int. Ed., 2010, 49, 3870. |