Footprint Catalysis. IX. Molecular Footprint Catalytic Cavities Imprinted with Chiral Hydantoins; Enantioselective Hydantoinase Mimics

Abstract

Imprinting using chiral 5-phenyhydantoins ((5R)- and (5S)-5-pheny-2,4-imidazolinedione) as templates could mark chiral molecular footprint-like cavities on a silica (alumina) gel surface. These cavities displayed evident enantioselective catalyses in reactions of (R)- and (S)-N-carboxyphenylglycine anhydrides, and (R)- and (S)-5-phenylhydantoins with 2,4-dinitrophenolate, respectively. A proposed mechanism and temperature effects on catalysis suggested that the enantioselectivities depended on the binding step of the catalysis.

Inorganic molecular imprinted titanium dioxide photocatalyst: synthesis, characterization and its application for efficient and selective degradation of phthalate esters

“…3+ ions doped nanoparticles. To activate the surface of the particles and clean away possible metallic impurities such as Fe 3+ and Zn 2+ , the obtained TiO 2 /SiO 2 nanoparticles (2 g) were refluxed with concentrated HCl (10 mL) for 5 h. 24,25 After being washed with deionized water (200-300 mL) and diluted NH 3 $H 2 O (pH 7-8, 200-400 mL) in order, the nanoparticles were added to 50 mL water containing 1.32 g AlCl 3 $6H 2 O, and then the solution pH was kept at 6.5 by adding diluted NH 3 $H 2 O. The doping of Al 3+ was achieved by aging the mixture at 80 C for 3 h. Then, the Al(OH) 3 floccules were removed by decanting, and the surplus Al(OH) 3 adhered on the surface of the particles was completely removed by washing with dilute HCl (pH 4, 200 mL).…”

“…As shown in Scheme 1, DEP may be adsorbed onto IMIP-P25 via two binding sites (C]O in the DEP molecule and Al 3+ in the IMIP), 24,25 resulting in the formation of a moderately stable surface complex between DEP and IMIP (eqn (1)),…”

Catalysis of an ester hydrolysis applying molecularly imprinted polymer shells based on an immobilised chiral template

“…Only a few examples have been presented in the literature demonstrating such an enantioselectivity of catalytically active molecularly imprinted materials [19][20][21][22][23][24][25][26][27]. Already in 1977, Wulff et al described chiral cavities generated in enzyme-analogue synthetic polymers [19].…”

“…Morihara et al have published several papers on the topic of ''molecular footprinting'', i.e., the synthesis of surface-imprinted silica particles. Such materials also showed enantioselective catalytic activities [21,22]. The main investigated reaction with respect to enantioselectivity of MIP catalysts is the hydrolysis of enantiomeric esters [23][24][25][26].…”

Synthesis of molecular imprinted polymer networks

“…The proposed mechanism of footprinting was reinforced by the observation that raising the temperature during the formation of the footprint to 75-80 ~ increased the catalytic specificity by a factor of 50 [15]. More recent work in this area includes the imprinting of chiral templates such as 5-phenylhydantoins [16], (S)-N- Grafting of an imprinted network to wide bore silica articles The proposed mechanism for footprint type imprinting -benzyl-alpha-methylbenzylamine [17] and bis-(Nbenzyloxycarbonyl-L-alanyl)amine [18]. Morihara's work is focused mainly on catalysis but, as in HPLC applications, the stability of the material is an important factor.…”