Ring Expansion of 4-Alkynylcyclobutenones. Synthesis of Piperidinoquinones, Highly Substituted Dihydrophenanthridines, Benzophenanthridines, and the Naturally Occurring Pyrrolophenanthridine, Assoanine

New synthetic routes to a variety of N-heterocyclic quinones and hydroquinones are described. These include thermolyses of 4-hydroxy-4-[4-N-(benzenesulfonyl)-4-aza-1,6-dialkynyl]cyclobutenones to piperidinoquinones and 4-hydroxy-4-[3-(N-phenylamino)-1-propynyl]cyclobutenones to dihydrophenanthridinediols. Included in the array of products available by this method are benzophenanthridines, indolophenanthridines, isoindoloindoles, and pyrrolophenanthridines. The methodology was employed in a five-step synthesis of the alkaloid assoanine starting with dimethyl squarate and indoline. The key step in all of these transformations is the ring expansion of appropriately substituted 4-hydroxy-4-alkynylcyclobutenones. These are envisaged to undergo electrocyclic ring opening to the corresponding enynylketenes which ring close to diradical intermediates that then lead to products via either radical additions to proximal alkyne moieties or undergo homolytic aromatic substitution to appropriately placed aryl groups. The synthetic scope and mechanism of the ring expansion reactions are discussed

Ring Expansion of 4-Alkynylcyclobutenones. Synthesis of Piperidinoquinones, Highly Substituted Dihydrophenanthridines, Benzophenanthridines, and the Naturally Occurring Pyrrolophenanthridine, Assoanine

New synthetic routes to a variety of N-heterocyclic quinones and hydroquinones are described. These include thermolyses of 4-hydroxy-4-[4-N-(benzenesulfonyl)-4-aza-1,6-dialkynyl]cyclobutenones to piperidinoquinones and 4-hydroxy-4-[3-(N-phenylamino)-1-propynyl]cyclobutenones to dihydrophenanthridinediols. Included in the array of products available by this method are benzophenanthridines, indolophenanthridines, isoindoloindoles, and pyrrolophenanthridines. The methodology was employed in a five-step synthesis of the alkaloid assoanine starting with dimethyl squarate and indoline. The key step in all of these transformations is the ring expansion of appropriately substituted 4-hydroxy-4-alkynylcyclobutenones. These are envisaged to undergo electrocyclic ring opening to the corresponding enynylketenes which ring close to diradical intermediates that then lead to products via either radical additions to proximal alkyne moieties or undergo homolytic aromatic substitution to appropriately placed aryl groups. The synthetic scope and mechanism of the ring expansion reactions are discussed

Supplementary document for Optical fiber tip integrated photoelectrochemical sensors - 5676255.pdf

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Supplementary document for A compact fiber-integrated scattering device based on mixed-phase TiO₂ for speckle spectrometer - 5702053.pdf

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Lithium Niobate Piezoelectric Actuator-Integrated Fiber Fabry-Pérot Tunable Filter with Ultrahigh Speed and Linearity

Fast-tunable filters play a crucial role in various applications including tunable lasers, high-speed optical communications, microwave photonics, and spectroscopy. However, current fiber Fabry-Pérot tunable filters (FFPTF) predominantly rely on piezoelectric transducers (PZT), which struggle to achieve rapid modulation with high repeatability and accuracy owing to hysteresis and creep effects. In this study, we demonstrate an FFPTF with high linearity (>0.99) and an approximate 1 MHz dynamic tuning frequency in the resonant state using the thickness–shear resonance of a Y-cut 163° lithium niobate (LiNbO3) sheet. The device exhibited a high overall performance with a finesse of 118 and an insertion loss of 2.54 dB, with well-designed fiber cavity configurations. This study provides a new approach for precise and rapid wavelength manipulation and selection, thereby paving the way for high-speed optical modulation and analyses

Ultracompact Multicore Fiber De-Multiplexer Using an Endface-Integrating Graphene Photodetector Array

The use of multicore fiber (MCF) aims to increase the fiber density with downsized fiber systems, which is constrained by a de-multiplexer with a large footprint that converts the MCF into numerous single-mode fibers and corresponding number of infrared photodetectors. In this study, we demonstrate an ultracompact seven-core fiber de-multiplexer by integrating a patterned single-layer graphene (SLG) photodetector array on a single fiber endface. An optimized electrode configuration was successfully fabricated with a strongly asymmetrical structure on patterned SLG. Owing to the efficient photocarrier separation at the built-in electric field across the metal-doped junction in graphene, we realized self-powered seven-core photodetection using the device. Remarkably, our device exhibits a coupling-free, miniaturized device volume with zero power consumption, a high transmittance, and low manufacturing cost. This device downsizes traditional bulky receiver modules to the micrometer scale with an atomical thickness, which may inspire the development of next-generation highly integrated optical and optoelectronic systems

Stacked polarimeters with twisted black phosphorus

The real-time, in-line analysis of light polarization is critical in optical communication networks, which suffers from the complex systems with numerous bulky opto-electro-mechanical elements tandemly arranged along optical path. Here, we propose a fiber-integrated polarimeter with nano-thickness by vertically stacking three two-dimensional (2D) materials based photodetection units. We demonstrate a self-power-calibrated, ultrafast, unambiguous detection of linear (LP) and circular polarized (CP) light according to the symmetry broken induced linear photogalvanic effects (LPGE) and circular photogalvanic effects (CPGE) in black phosphorous (BP) units, which are twistedly stacked to substitute traditional mechanical rotation of polarizers. As a demonstration, we achieve Hadamard single-pixel polarimetric imaging by the polarimeter to recognize the polarization distributions, showing potential in high-speed polarization-division-multiplexed imaging and real-time polarized endoscopy. This work provides a new strategy for next-generation ultracompact optical and optoelectronic systems, and guides a way for developing high-resolution arrayed devices with multifunctional pixels

All-Fibre Label-Free Nano-Sensor for Real-Time in situ Early Monitoring of Cellular Apoptosis

The achievement of all-fibre functional nano-modules for subcellular label-free measurement has long been pursued due to the limitations of manufacturing techniques. In this paper, a compact all-fibre label-free nano-sensor composed of a fibre taper and zinc oxide nano-gratings is designed and applied for the early monitoring of apoptosis in single living cells. Because of its nanoscale dimensions, mechanical flexibility and minimal cytotoxicity to cells, the sensing module can be loaded in cells for long-term in situ tracking with high sensitivity. A gradual increase in the nuclear refractive index during the apoptosis process is observed, revealing the increase in molecular density and the decrease in cell volume. The strategy used in this study not only contributes to the understanding of internal environmental variations during cellular apoptosis but also provides a new platform for non-fluorescent all-fibre devices to investigate cellular events and to promote new progress in fundamental cell biochemical engineering

Identification and In Vivo Evaluation of Myelination Agent PIPE-3297, a Selective Kappa Opioid Receptor Agonist Devoid of β‑Arrestin‑2 Recruitment Efficacy

Structure–activity relationship studies led to the discovery of PIPE-3297, a fully efficacious and selective kappa opioid receptor (KOR) agonist. PIPE-3297, a potent activator of G-protein signaling (GTPγS EC50 = 1.1 nM, 91% Emax), did not elicit a β-arrestin-2 recruitment functional response (Emax < 10%). Receptor occupancy experiments performed with the novel KOR radiotracer [3H]-PIPE-3113 revealed that subcutaneous (s.c.) administration of PIPE-3297 at 30 mg/kg in mice achieved 90% occupancy of the KOR in the CNS 1 h post dose. A single subcutaneous dose of PIPE-3297 in healthy mice produced a statistically significant increase of mature oligodendrocytes (P < 0.0001) in the KOR-enriched striatum, an effect that was not observed in animals predosed with the selective KOR antagonist norbinaltorphimine. An equivalent dose given to mice in an open-field activity-monitoring system revealed a small KOR-independent decrease in total locomotor activity versus vehicle measured between 60 and 75 min post dose. Daily doses of PIPE-3297 at both 3 and 30 mg/kg s.c. reduced the disease score in the mouse experimental autoimmune encephalomyelitis (EAE) model. Visually evoked potential (VEP) N1 latencies were also significantly improved versus vehicle in both dose groups, and latencies matched those of untreated animals. Taken together, these findings highlight the potential therapeutic value of functionally selective G-protein KOR agonists in demyelinating disease, which may avoid the sedating side effects typically associated with classical nonbiased KOR agonists

Synthesis and in Vivo Evaluation of Phenethylpiperazine Amides: Selective 5-Hydroxytryptamine_2A Receptor Antagonists for the Treatment of Insomnia

Recent developments in sleep research suggest that antagonism of the serotonin 5-HT2A receptor may improve sleep maintenance insomnia. We herein report the discovery of a series of potent and selective serotonin 5-HT2A receptor antagonists based on a phenethylpiperazine amide core structure. When tested in a rat sleep pharmacology model, these compounds increased both sleep consolidation and deep sleep. Within this series of compounds, an improvement in the metabolic stability of early leads was achieved by introducing a carbonyl group into the phenethylpiperazine linker. Of note, compounds 14 and 27 exhibited potent 5-HT2A receptor binding affinity, high selectivity over the 5-HT2C receptor, favorable CNS partitioning, and good pharmacokinetic and early safety profiles. In vivo, these two compounds showed dose-dependent, statistically significant improvements on deep sleep (δ power) and sleep consolidation at doses as low as 0.1 mg/kg