A mild and convenient method for the synthesis of reverse glycosyl fluorides (RGFs) has been developed that is based on the silver‐promoted radical dehydroxymethylative fluorination of carbohydrates. A salient feature of the reaction is that furanoid and pyranoid carbohydrates furnish structurally diverse RGFs bearing a wide variety of functional groups in good to excellent yields. Intramolecular hydrogen atom transfer experiments revealed that the reaction involves an underexploited radical fluorination that proceeds via β‐fragmentation of sugar‐derived primary alkoxyl radicals. Structurally divergent RGFs were obtained by catalytic C−F bond activation, and our method thus offers a concise and efficient strategy for the synthesis of reverse glycosides by late‐stage diversification of RGFs. The potential of this method is showcased by the preparation and diversification of sotagliflozin, leading to the discovery of a promising SGLT2 inhibitor candidate.
An efficient protocol for synthesizing
reverse glycosyl fluorides is described, relying on silver-promoted
decarboxylative fluorination of structurally diverse pentofuran- and
hexopyranuronic acids under the mild reaction conditions. The potential
applications of the reaction are further demonstrated by converting
readily available d-uronic acid derivatives into uncommon d-/l-glycosyl fluorides through a C1-to-C5 switch strategy.
The reaction mechanism is corroborated by 5-exo-trig radical cyclization of allyl α-d-C-glucopyranuronic
acid triggered by decarboxylative fluorination.
A facile, one‐pot synthesis of 1H‐indazoles featuring a Cu‐catalyzed C–H ortho‐hydroxylation and N–N bond‐formation sequence with the use of pure oxygen as the terminal oxidant was developed. The reaction of readily available 2‐arylaminobenzonitriles with various organometallic reagents led to ortho‐arylamino N–H ketimine species. Subsequent Cu‐catalyzed hydroxylation at the ortho position of the aromatic ring followed by N–N bond formation in DMSO under a pure‐oxygen atmosphere afforded a wide variety of 1‐(ortho‐hydroxyaryl)‐1H‐indazoles in good to excellent yields. This efficient method does not require the utilization of noble‐metal catalysts, elaborate directing groups, or privileged ligands.
The study presents a general framework for discovering underlying Partial Differential Equations (PDEs) using measured spatiotemporal data. The method, called Sparse Spatiotemporal System Discovery (S 3 d), decides which physical terms are necessary and which can be removed (because they are physically negligible in the sense that they do not affect the dynamics too much) from a pool of candidate functions. The method is built on the recent development of Sparse Bayesian Learning; which enforces the sparsity in the to-beidentified PDEs, and therefore can balance the model complexity and fitting error with theoretical guarantees. Without leveraging prior knowledge or assumptions in the discovery process, we use an automated approach to discover ten types of PDEs, including the famous Navier-Stokes and sine-Gordon equations, from simulation data alone. Moreover, we demonstrate our data-driven discovery process with the Complex Ginzburg-Landau Equation (CGLE) using data measured from a traveling-wave convection experiment. Our machine discovery approach presents solutions that has the potential to inspire, support and assist physicists for the establishment of physical laws from measured spatiotemporal data, especially in notorious fields that are often too complex to allow a straightforward establishment of physical law, such as biophysics, fluid dynamics, neuroscience or nonlinear optics.
Salt stress is one important factor influencing the growth and development of plants, and salt tolerance of plants is a result of combined action of multiple genes and mechanisms. Rosa rugosa is not only an important ornamental plant, but also the natural aromatic plant of high value. Wild R. rugosa which is naturally distributed on the coast and islands of China has a good salt tolerance due to the special living environment. Here, the vacuolar Na(+)/H(+) reverse transporter gene (NHX1) and the vacuolar H(+)-ATPase subunit C gene (VHA-c) closely related to plant salt tolerance were isolated from wild R. rugosa, and the expression patterns in R. rugosa leaves of the two genes under NaCl stress were determined by real-time quantitative fluorescence PCR. The results showed that the RrNHX1 protein is a constitutive Na(+)/H(+) reverse transporter, the expression of the RrNHX1 gene first increased and then decreased with the increasing salt concentration, and had a time-controlled effect. The RrVHA-c gene is suggestive of the housekeeping feature, its expression pattern showed a similar variation trend with the RrNHX1 gene under the stress of different concentrations of NaCl, and its temporal expression level under 200 mM NaCl stress presented bimodal change. These findings indicated that RrNHX1 and RrVHA-c genes are closely associated with the salt tolerance trait of wild R. rugosa.
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