Selective Hydrolysis of Nonactivated Aryl Esters at pH 7 through Cooperative Catalysis

Abstract

Most reported artificial esterases only hydrolyze highly activated substrates. We here report synthetic catalysts that hydrolyze nonactivated aryl esters at pH 7, via cooperative action of a thiourea group that mimics the oxyanion hole of a serine protease and a nearby nucleophilic/basic pyridyl group. The molecularly imprinted active site distinguishes subtle structural changes in the substrate, including elongation of the acyl chain by two carbons or shift of a remote methyl group by one carbon.

Figure 1.

Amount of p-nitrophenoxide formed as a function of time in a 25 mM HEPES buffer (pH 7.0) at 40 °C, calculated based on an extinction coefficient of ε₄₀₀ = 0.0216 μM⁻¹ cm⁻¹. [PNPH] = 100 μM. [MINP_3b(2d+6b)] = 0.2 μM.

Figure 2.

Hydrolysis of a mixture of 7 and 9 in 25 mM HEPES buffer (pH 7) at 60 °C after (a) 0 h, (b) 8 h, and (c) 16 h, monitored by gas chromatography using p-xylene (300 μM) as an internal standard. [7] = [9] = 300 μM. [MINP_3b(2d+6b)] = 15 μM.

Scheme 1.

Preparation of MINP catalysts with thiourea and a catalytic pyridyl group in the active site. The surface ligands (from 5) are omitted in the drawing for clarity.