Abstract
Deracemization is a powerful method by which a racemic mixture can be transformed into an excess of one enantiomer with the aid of chiral auxiliaries, but has been applied only to small chiral molecular systems. Here we report a deracemization of a racemic double-stranded spiroborate helicate containing a bisporphyrin unit upon encapsulation of chiral aromatic guests between the bisporphyrin. The chiral guest-included helicate is kinetically stable, existing as a mixture of right- and left-handed double helices, which eventually undergo an inversion of the helicity triggered by water resulting from the water-mediated reversible diastereoselective B-O bond cleavage/reformation of the spiroborate groups, thus producing an optically-active helicate with a high enantioselectivity. Quantum chemical calculations suggest that the stereospecific CH-π interactions between the porphyrin hydrogen atoms of the helicate and an aromatic pendant group of the chiral guest play a key role in the enhancement of the helical handedness of the helicate.
| Original language | English |
|---|---|
| Article number | 1457 |
| Journal | Nature Communications |
| Volume | 10 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 1 2019 |
Funding
The authors thank Daisuke Taura, Akio Urushima, and Manabu Itakura (Nagoya University) for their help in the experimental assistance and also Hiroyuki Asanuma and Hiromu Kashida (Nagoya University) for providing advice regarding the fluorescence quenching. This work was supported in part by JSPS KAKENHI (Grant-in-Aid for Scientific Research (S), No. 25220804 (E.Y.), Grant-in-Aid for Specially Promoted Research, No. 18H05209 (E.Y.), and Grant-in-Aid for Young Scientists (B), No. 17K14470 (N.O.)). S.Y. expresses his thanks for a JSPS Research Fellowship for Young Scientists (No. 9119).
| Funders | Funder number |
|---|---|
| Japan Society for the Promotion of Science | 25220804, 17K14470, 18H05209, 9119 |