10.1016/j.catcom.2020.106098
Jing Lv et al. present the development of a novel zwitterionic catalyst containing imidazole, carboxyl, and amino functional groups to catalyze the retro-aldol condensation of fructose to produce 1,3-dihydroxyacetone (DHA). The study demonstrates that the catalyst achieves a DHA yield of 27.9% and selectivity of 46.5% after 2 hours of reaction at pH 9.5 and 85°C. The catalyst mimics the active site of aldolase enzymes, with charged functional groups facilitating electron induction and proton transfer, which are crucial for the selective conversion of fructose to DHA under mild conditions. The research highlights the importance of pH, temperature, and the synergistic effect of functional groups in achieving high catalytic efficiency. The study also proposes a possible catalytic mechanism involving ring-opening of fructose, rotation of the C3-C4 bond, and subsequent cleavage to form DHA.
10.1002/chem.200390110
The study focuses on the development and application of fluorogenic stereochemical probes for transaldolases, enzymes that catalyze the transfer of dihydroxyacetone between sugar phosphates. The researchers synthesized two probes, 6-O-coumarinyl-fructose (1) and its 5-deoxy derivative (2), which are designed to measure the stereoselectivity of transaldolases. These probes work by undergoing a retro-aldolization reaction catalyzed by transaldolases, producing a primary product that further reacts to release a strongly fluorescent product, umbelliferone, upon elimination in the presence of bovine serum albumin (BSA). The study also involved the synthesis of a stereoisomer related to tagatose (3), which serves as a control to assess the stereoselectivity of the enzymes. The purpose of these chemicals is to provide a fluorogenic assay system for transaldolases, suitable for high-throughput screening of enzyme libraries, particularly for directed evolution experiments aiming to alter enzyme stereoselectivity. The study includes the use of various other chemicals, such as erythrose 4-phosphate as a natural acceptor to shift the reaction equilibrium, and a range of solvents and reagents in the synthesis and purification processes.
10.1016/S0040-4020(98)01173-9
The study explores the use of the HOF·CH3CN complex for the a-hydroxylation of various carbonyl compounds. The HOF·CH3CN complex is prepared by bubbling nitrogen-diluted fluorine through aqueous acetonitrile and serves as an efficient oxygen transfer agent. It is used to oxidize the a-carbon of carbonyl compounds, converting them into their respective a-hydroxy derivatives. The study involves the use of trimethylsilyl enol ethers derived from ketones, esters, and acids as substrates. These enol ethers react with the HOF·CH3CN complex under mild conditions, typically at room temperature or below, yielding high-quality a-hydroxy products. The study demonstrates the versatility and efficiency of this method for a wide range of carbonyl compounds, including cyclic ketones, aliphatic ketones, esters, and carboxylic acids, with yields often exceeding 80%. The findings highlight the potential of the HOF·CH3CN complex as a valuable tool in organic synthesis for the functionalization of carbonyl compounds.
