نتایج جستجو برای: intermediate ring
تعداد نتایج: 251397 فیلتر نتایج به سال:
To solve the practical problem of Stirling engine piston ring, numerical model on friction and lubrication were established based average Reynolds equation theory. Numerical calculation results show: rings are in mixed state which gas film micro-convex body contact existing simultaneously; pressure is 2 orders magnitude less than pressure; approximately linearly related to mean pressure. Simula...
For many E3 ligases, a mobile RING (Really Interesting New Gene) domain stimulates ubiquitin (Ub) transfer from a thioester-linked E2∼Ub intermediate to a lysine on a remotely bound disordered substrate. One such E3 is the gigantic, multisubunit 1.2-MDa anaphase-promoting complex/cyclosome (APC), which controls cell division by ubiquitinating cell cycle regulators to drive their timely degradat...
An intriguing stepwise diradical mechanism of the dimerization of the reactive intermediate (thiocarbonyl S-methanide) appearing in the reaction of phenyl selenophen-2-yl thioketone with diazomethane was studied by means of computational methods. The preferred formation of the unusual macroheterocycle, competitive with the 1,3-ring closure leading to a thiirane and the head-to-head dimerization...
Figure 1. (A) The b5 ion is generated by collision induced dissociation resulting in formation of the oxazolone ring through attack of the oxygen lone pair on the newly formed terminal carbonyl group. (B) N-terminal nucleophilic attack of the oxazolone ring to form the macrocycle. (C) The resultant macrocyclic intermediate undergoes ring opening to give sequence scrambled b5 ions. N.B. Numberin...
The linear ubiquitin chain assembly complex (LUBAC) is a RING E3 ligase that regulates immune and inflammatory signalling pathways. Unlike classical RING E3 ligases, LUBAC determines the type of ubiquitin chain being formed, an activity normally associated with the E2 enzyme. We show that the RING-in-between-RING (RBR)-containing region of HOIP--the catalytic subunit of LUBAC--is sufficient to ...
Total syntheses of (+)-cinereain and (−)-janoxepin, two fungal cyclotripeptides featuring a complex heterocyclic core interesting phytotoxic antimalarial activities, have been achieved in convergent manner. A key step this synthesis is one-pot cascade initiated by the cyclocondensation fragments—a hindered 2-vinylcyclopropane-1-acyl fluoride an electron-deficient cyclic amidine—to release react...
Gambieric acid A (GAA) and its congeners belong to the family of marine polycyclic ether natural products. Their highly complex molecular architecture and unique biological activities have been of intense interest within the synthetic community. We have previously reported the first total synthesis, stereochemical reassignment, and preliminary structure-activity relationships of GAA. Here we di...
Electrophilic AlIII species have long dominated the aluminum reactivity towards arenes. Recently, nucleophilic low-valent AlI aluminyl anions showcased oxidative additions arenes C−C and/or C−H bonds. Herein, we communicate compelling evidence of an AlII radical addition reaction to benzene ring. The electron reduction a ligand stabilized precursor with KC8 in furnishes double ring instead bond...
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