Scheme 2. Examples for the use of cyclic N,O-acetals as a stereocontrol element. a) For dihydroxylation. b) For epoxidation. c) For hydrogenation. NMO = N-methylmorpholine-N-oxide, THF = tetrahydrofuran. Scheme 3. Examples for the use of cyclic N,O-acetals as a diversitygenerating element. TBS = tert-butyldimethylsilyl.
Catalytic asymmetric synthesis of N-heterocyclic glycosides free of protecting and directing groups is reported. The key reaction is highlighted by the atom-efficient and regioselective addition of unprotected pyrimidines to highly functionalized alkoxyallene. Numerous acyclic and cyclic N-heterocyclic glycosides are accessed with minimal formation of organic byproducts. The synthetic utility of the reaction is demonstrated by the first catalytic asymmetric synthesis of anticancer pharmaceutical (-)-Tegafur and stereoselective synthesis of an oxepane nucleoside derivative.
The first gold-catalyzed intermolecular coupling of alkynoates and allylic ethers invoking alkoxy addition and [3,3]-sigmatropic rearrangement as the key mechanism has been developed. Remarkably, the reaction showed complete chemoselectivity toward the pathway initiated by the alkoxy addition to alkynes. This unprecedented reactivity led to a new access to diversely substituted β-alkoxyacrylates in a highly efficient manner.
In this paper, the methodology of a CA (Control Allocation) based FTNCS (Fault-Tolerant Networked Control System) is proposed. Control allocation is a control surface management technique by redistributing the redundant control surfaces in overactuated systems. In modern high performance aircrafts, they adopt many redundant control surfaces to provide high performance and to satisfy various tactical requirements. Moreover, redundant control surfaces provide an opportunity to compensate performance degradation due to failures in more than one actuator by re-allocating redundant control surfaces. Simulation results with an F-18 HARV demonstrate that the proposed CA based FTNCS can achieve a fast and accurate tracking performance even in the presence of actuator faults.
A highly efficient and stereoselective synthetic pathway towards trans-3,4-dihydroxy-2-alkylpyrrolidines and piperidines is described. The nature of the protecting groups on the hydroxyl moieties played a crucial role on the trans selectivity. By using this method, a concise total synthesis of (-)-2-epilentiginosine has been achieved.
Recent developments in semiconductor technology have resulted in advancements in device manufacturing processes, especially when plasma discharges are required. In this investigation, an inductively coupled plasma (ICP) discharge with a radio frequency bias simulation was explored. A 2D symmetric structure is presented and a modified fluid model is applied using the electron distribution function (EEDF). This is achieved by using a two-term Boltzmann approximation and an ion energy distribution function (IEDF) with the particle-in-cell method. In addition, the heat transfer and gas flow effects are considered to improve the simulation results. The application of multi-physics components to the ICP discharge displays hybrid-like results using COMSOL[1].
Ringbildung: Eine neue Strategie zur Synthese cyclischer Amine nutzt ein stereochemisch definiertes cyclisches N,O‐Acetal als wichtigstes stereokontrollierendes und Diversität erzeugendes Element. Das Acetal, das seine stereochemische Integrität über alle katalytischen Umwandlungen bewahrt, wurde durch asymmetrische Hydroaminierung eines Alkoxyallens mit dem chiralen Liganden L* und anschließende Ringschlussmetathese erhalten.
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