Photoenzymatic Enantioselective Synthesis of Oxygen-Containing Benzo-Fused Heterocycles

New-to-nature biocatalysis in organic synthesis has recently emerged as a green and powerful strategy for the preparation of valuable chiral products, among which chiral oxygen-containing benzo-fused heterocycles are important structural motifs in pharmaceutical industry. However, the asymmetric synthesis of these compounds through radical-mediated methods is challenging. Herein, a novel asymmetric radical-mediated photoenzymatic synthesis strategy is developed to realize the efficient enantioselective synthesis of oxygen-containing benzo-fused heterocycles through structure-guided engineering of a flavin-dependent ‘ene’-reductase GluER. It shows that variant GluER-W100H could efficiently produce various benzoxepinones, chromanone and indanone with different benzo-fused rings in high yields with great stereoselectivities under visible light. Moreover, these results are well supported by mechanistic experiments, revealing that this photoenzymatic process involves electron donor-acceptor complex formation, single electron transfer and hydrogen atom transfer. Therefore, we provide an alternative green approach for efficient chemoenzymatic synthesis of important chiral skeletons of bioactive pharmaceuticals.     

SSZ-39分子筛的合成及应用进展

近年来,小孔八元环SSZ-39分子筛因具有特殊的孔道结构和物理化学性质,在小分子择形催化反应中展现出相对优异的催化活性、抗积碳性和水热稳定性.本文概述了SSZ-39分子筛的合成历程,包括不同种类有机模板剂的使用、特定硅源铝源的选择以及凝胶组成的调控等;简要总结了SSZ-39分子筛在甲醇制低碳烯烃、氮氧化物的选择性催化还...     

Super-Resolution Two-Photon Fluorescence Tomography Through the Phase-Shifted Optical Beatings of Bessel Beams for High-Resolution Deeper Tissue 3D Imaging

A novel z-scanning-free epi-detected super-resolution two-photon fluorescence tomography (TPFT) technique enabling super-resolution deeper tissue 3D imaging is reported. To accomplish this, a unique method is conceived by generating the phase-shifted optical beatings of Bessel beams (PS-OB³) with a spatial light modulator (SLM) to break the diffraction limit for enhancing both the lateral and axial resolutions as well as improving the penetration depth in TPFT for super-resolution deeper tissue imaging. By electronically varying the optical beating frequency and the phase shifts of the beating patterns through SLM, the depth-resolved TPF signals about the volumetric tissue are encoded in the spatial frequency domain and hence, a series of depth-resolved TPF images can be retrieved by implementing inverse fast Fourier transform without a need of mechanical depth-scanning. PS-OB³ TPFT provides ≈1.3- and 2-fold improvements in lateral and axial resolutions in comparison with conventional point-scan TPF imaging. It is also illustrated that the epi-detected PS-OB³ TPFT imaging with inherent scattering-resilient properties of the Bessel beams employed gives over 2-fold improvement in imaging depth in porcine brain tissue compared to conventional point-scan Gaussian beam TPF imaging. The z-scanning-free optical sectioning ability of PS-OB³ method developed in TPFT is universal, which can be readily extended to practically any other nonlinear optical imaging modalities for super-resolution deeper 3D imaging in biological and biomedical tissues.