Imprinted micelles for chiral recognition in water: shape, depth, and number of recognition sites

Abstract

Chiral molecular recognition is important to biology, separation, and asymmetric catalysis. Because there is no direct correlation between the chiralities of the host and the guest, it is difficult to design a molecular receptor for a chiral guest in a rational manner. By cross-linking surfactant micelles containing chiral template molecules, we obtained chiral nanoparticle receptors for a number of 4-hydroxyproline derivatives. Molecular imprinting allowed us to transfer the chiral information directly from the guest to host, making the molecular recognition between the two highly predictable. Hydrophobic interactions between the host and the guest contributed strongly to the enantio- and diastereoselective differentiation of these compounds in water, whereas ion-pair interactions, which happened near the surface of the micelle, were less discriminating. The chiral recognition could be modulated by tuning the size and shape of the binding pockets.

Fig 1

ITC titration curves obtained at 298 K for the binding of (a) 4 (0.12 mM) by MINP(4) (0.01 mM ) in Millipore water, and (b) 4 (0.12 mM) by MINP(4) (0.01 mM) in 50 mM Tris buffer pH 7.4. The data correspond to entries 1 and 2, respectively, in Table 1. Additional ITC titration curves can be found in the Electronic Supplementary Information (ESI).

Fig 2

Schematic comparison of binding selectivity of MINP(4) and MINP(7).

Scheme 1

Preparation of MINP by surface–core double cross-linking of template-containing micelle of 1.