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排序方式: 共有313条查询结果,搜索用时 15 毫秒
311.
Carla Calvó-Tusell Dr. Zhen Liu Dr. Kai Chen Prof. Dr. Frances H. Arnold Dr. Marc Garcia-Borràs 《Angewandte Chemie (International ed. in English)》2023,62(35):e202303879
We report a computationally driven approach to access enantiodivergent enzymatic carbene N−H insertions catalyzed by P411 enzymes. Computational modeling was employed to rationally guide engineering efforts to control the accessible conformations of a key lactone-carbene (LAC) intermediate in the enzyme active site by installing a new H-bond anchoring point. This H-bonding interaction controls the relative orientation of the reactive carbene intermediate, orienting it for an enantioselective N-nucleophilic attack by the amine substrate. By combining MD simulations and site-saturation mutagenesis and screening targeted to only two key residues, we were able to reverse the stereoselectivity of previously engineered S-selective P411 enzymes. The resulting variant, L5_FL-B3 , accepts a broad scope of amine substrates for N−H insertion with excellent yields (up to >99 %), high efficiency (up to 12 300 TTN), and good enantiocontrol (up to 7 : 93 er). 相似文献
312.
Protoglobin-Catalyzed Formation of cis-Trifluoromethyl-Substituted Cyclopropanes by Carbene Transfer
Lucas Schaus Dr. Anuvab Das Dr. Anders M. Knight Dr. Gonzalo Jimenez-Osés Prof. Dr. K. N. Houk Dr. Marc Garcia-Borràs Prof. Dr. Frances H. Arnold Prof. Dr. Xiongyi Huang 《Angewandte Chemie (International ed. in English)》2023,62(4):e202208936
Trifluoromethyl-substituted cyclopropanes (CF3-CPAs) constitute an important class of compounds for drug discovery. While several methods have been developed for synthesis of trans-CF3-CPAs, stereoselective production of corresponding cis-diastereomers remains a formidable challenge. We report a biocatalyst for diastereo- and enantio-selective synthesis of cis-CF3-CPAs with activity on a variety of alkenes. We found that an engineered protoglobin from Aeropyrnum pernix (ApePgb) can catalyze this unusual reaction at preparative scale with low-to-excellent yield (6–55 %) and enantioselectivity (17–99 % ee), depending on the substrate. Computational studies revealed that the steric environment in the active site of the protoglobin forced iron-carbenoid and substrates to adopt a pro-cis near-attack conformation. This work demonstrates the capability of enzyme catalysts to tackle challenging chemistry problems and provides a powerful means to expand the structural diversity of CF3-CPAs for drug discovery. 相似文献
313.
Ezio Rizzardo John Chiefari Bill Y.K. Chong Frances Ercole Julia Krstina Justine Jeffery Tam P.T. Le Roshan T.A. Mayadunne Gordon F. Meijs Catherine L. Moad Graeme Moad San H. Thang 《Macromolecular Symposia》1999,143(1):291-307
This paper describes a versatile and effective method for the control of free radical polymerization and its use in the preparation of narrow polydispersity polymers of various architectures. Living character is conferred to conventional free radical polymerization by the addition of a thiocarbonylthio compound of general structure S=C(Z)SR, for example, S=C(Ph)SC(CH3)2Ph. The mechanism involves Reversible Addition-Fragmentation chain Transfer and, for convenience of referral, we have designated it the RAFT polymerization. The process is compatible with a very wide range of monomers including functional monomers such as acrylic acid, hydroxyethyl methacrylate, and dimethylaminoethyl methacrylate. Examples of narrow polydispersity (≤1.2) homopolymers, copolymers, gradient copolymers, end-functional polymers, star polymers, A-B diblock and A-B-A triblock copolymers are presented. 相似文献