A new strategy for the catalytic enantioselective α-arylation of N-acyloxazolidinones with chiral copper(II)-bisoxazoline complexes and diaryliodonium salts is described. The mild catalytic conditions are operationally simple, produce valuable synthetic building blocks in excellent yields and enantioselectivities, and can be applied to the synthesis of important nonsteroidal anti-inflammatory agents and their analogues.
The nicotinic acetylcholine receptor (nAChR) is a ligand-gated ion channel composed of 5 protein subunits arranged around a central cation selective pore. Several classes of natural and synthetic insecticides mediate their effect through interacting at nAChRs. This review examines the basic pharmacology of the neonicotinoids and related chemistry, with an emphasis on sapfeeding insects from the order Hemiptera, the principle pest target for such insecticides. Although the receptor subunit stoichiometry for endogenous invertebrate nAChRs is unknown, there is clear evidence for the existence of distinct neonicotinoid binding sites in native insect preparations, which reflects the predicted wide repertoire of nAChRs and differing pharmacology within this insecticide class. The spinosyns are principally used to control chewing pests such as Lepidoptera, whilst nereistoxin analogues are used on pests of rice and vegetables through contact and systemic action, the pharmacology of both these insecticides is unique and different to that of the neonicotinoids.
The insecticidal effects of ω‐hexatoxin‐Hv1a, κ‐hexatoxin‐Hv1c and ω/κ‐hexatoxin‐Hv1h are currently attributed to action at calcium and potassium channels. By characterizing the binding of these toxins to neuronal membranes, we show that they have more potent effects as positive allosteric modulators (PAMs) of insect nicotinic acetylcholine receptors (nAChRs), consistent with their neuroexcitatory toxicology. Alanine scanning analysis of ω‐hexatoxin‐Hv1a reveals a structure–activity relationship for binding that mirrors that for insecticidal activity. Spinosyn A does not compete with ω‐hexatoxin‐Hv‐1a for binding, and we show that these two PAMs have distinct pharmacology of binding indicating that they act at different receptor populations. These toxins represent valuable tools for the characterization of insect nAChRs and for the development of more selective agrochemicals.
The development of novel and safe
insecticides remains an important
need for a growing world population to protect crops and animal and
human health. New chemotypes modulating the insect nicotinic acetylcholine
receptors have been recently brought to the agricultural market, yet
with limited understanding of their molecular interactions at their
target receptor. Herein, we disclose the first crystal structures
of these insecticides, namely, sulfoxaflor, flupyradifurone, triflumezopyrim,
flupyrimin, and the experimental compound, dicloromezotiaz, in a double-mutated
acetylcholine-binding protein which mimics the insect-ion-channel
orthosteric site. Enabled by these findings, we discovered novel pharmacophores
with a related mode of action, and we describe herein their design,
synthesis, and biological evaluation.
The design of a new potent nonsteroidal ecdysone agonist led to the discovery of a diethylaminosulfur trifluoride (DAST)-mediated cyclization of α,α-disubstituted-α-acylaminoketones. The resulting fluorooxazolines can be ring-opened or selectively substituted by a range of nucleophiles to provide in high yields a diverse array of unprecedented heterocyclic frameworks.
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