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1.
Nature ; 626(7999): 574-582, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38086421

RESUMEN

The intrinsic mechanisms that regulate neurotoxic versus neuroprotective astrocyte phenotypes and their effects on central nervous system degeneration and repair remain poorly understood. Here we show that injured white matter astrocytes differentiate into two distinct C3-positive and C3-negative reactive populations, previously simplified as neurotoxic (A1) and neuroprotective (A2)1,2, which can be further subdivided into unique subpopulations defined by proliferation and differential gene expression signatures. We find the balance of neurotoxic versus neuroprotective astrocytes is regulated by discrete pools of compartmented cyclic adenosine monophosphate derived from soluble adenylyl cyclase and show that proliferating neuroprotective astrocytes inhibit microglial activation and downstream neurotoxic astrocyte differentiation to promote retinal ganglion cell survival. Finally, we report a new, therapeutically tractable viral vector to specifically target optic nerve head astrocytes and show that raising nuclear or depleting cytoplasmic cyclic AMP in reactive astrocytes inhibits deleterious microglial or macrophage cell activation and promotes retinal ganglion cell survival after optic nerve injury. Thus, soluble adenylyl cyclase and compartmented, nuclear- and cytoplasmic-localized cyclic adenosine monophosphate in reactive astrocytes act as a molecular switch for neuroprotective astrocyte reactivity that can be targeted to inhibit microglial activation and neurotoxic astrocyte differentiation to therapeutic effect. These data expand on and define new reactive astrocyte subtypes and represent a step towards the development of gliotherapeutics for the treatment of glaucoma and other optic neuropathies.


Asunto(s)
Astrocitos , Neuroprotección , Adenilil Ciclasas/metabolismo , Astrocitos/citología , Astrocitos/enzimología , Astrocitos/metabolismo , Diferenciación Celular , Núcleo Celular/metabolismo , Supervivencia Celular , AMP Cíclico/metabolismo , Citoplasma/metabolismo , Macrófagos/metabolismo , Macrófagos/patología , Microglía/metabolismo , Microglía/patología , Traumatismos del Nervio Óptico/metabolismo , Traumatismos del Nervio Óptico/patología , Traumatismos del Nervio Óptico/terapia , Células Ganglionares de la Retina/citología , Células Ganglionares de la Retina/metabolismo , Sustancia Blanca/metabolismo , Sustancia Blanca/patología , Glaucoma/patología , Glaucoma/terapia
2.
bioRxiv ; 2023 Apr 17.
Artículo en Inglés | MEDLINE | ID: mdl-37131765

RESUMEN

Malignant astroctyoma and glioblastoma are diffuse CNS tumors that have markedly similar features, including microvascular proliferation and necrosis, and the latter presents higher grade and poorer survival. The Isocitrate dehydrogenase 1/2 (IDH) mutation further predicts improved survival and is present in oligodendroglioma and astrocytoma. The latter are more prevalent in younger populations with a median age of 37 years at diagnosis as compared to glioblastoma with a median age of 641,2. These tumors frequently have co-occurring ATRX and/or TP53 mutations (Brat et al., 2021). The IDH mutation is known to cause dysregulation of the hypoxia response broadly in CNS tumors and subsequent reduction in both tumor growth and treatment resistance. The frequency of tumor recurrence is high for diffuse CNS tumors. Understanding the mechanism and potential molecular targets enhancing treatment resistance and local invasion in IDH mutant diffuse glioma is necessary for developing new treatment strategies for better tumor control and improving overall survival. Recent evidence highlights the importance of local foci in IDH mutant glioma with an accelerated stress response as responsible for recurrence in these tumors. Here, we demonstrate that LonP1 drives NRF2 and subsequent proneural mesenchymal transition interdependent with the IDH mutation in response to stress and other tumor microenvironment cues. Our findings provide further evidence that targeting LonP1 may be a crucial strategy for improving the standard-of-care treatment in IDH mutant diffuse astrocytoma.

3.
Acta Crystallogr E Crystallogr Commun ; 79(Pt 4): 406-409, 2023 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-37057004

RESUMEN

The crystal structures of two rubrene derivatives, 5,11-diphenyl-6,12-bis-[4-(tri-fluoro-meth-yl)phen-yl]tetra-cene, C44H26F6, and 5,11-bis-(4-tert-butyl-phen-yl)-6,12-di-phenyl-tetra-cene, C50H44, are presented. Each are substituted on diagonal (5/11) phenyl rings. Each derivative has one polymorph reported previously. A discussion of the differences between each derivative and its previously reported polymorph is provided. The triclinic packing of the CF3-substituted structure is similar to the packing of the parent rubrene's triclinic polymorph. In the tert-butyl-substituted structure, a planar tetra-cene core formed, which has been hypothesized but never published. Crystallization conditions are provided as they differ from previous reports.

4.
Org Lett ; 25(1): 146-151, 2023 01 13.
Artículo en Inglés | MEDLINE | ID: mdl-36583549

RESUMEN

Directing groups are a common strategy to target traditionally inert bonds, with an easily removable directing group being ideal. Herein we disclose our method for rhodium-catalyzed C-O bond functionalization of N-pyridylimidates using a recyclable and traceless amine directing group. In addition to the substrate scope, we discuss the behavior of this class of compounds and how that behavior affects their reactivity.


Asunto(s)
Rodio , Catálisis , Rodio/química , Piridinas/química
5.
J Phys Chem A ; 126(36): 6194-6202, 2022 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-36067456

RESUMEN

The microwave spectrum of pivalic sulfuric anhydride, (CH3)3CCOOSO2OH (PivSA), has been observed by rotational spectroscopy. The compound was formed by the reaction of SO3 with (CH3)3CCOOH (pivalic acid) in a supersonic jet in a manner analogous to that previously observed with other carboxylic acids. Computational analysis indicates that the reaction is best described as a pericyclic process coupled with a 60° rotation of the t-butyl group. Product formation can occur through either a sequential (two-step) or a concerted (one-step) pathway. The former involves an internal rotation of the t-butyl group through a 0.11 kcal/mol barrier followed by the pericyclic reaction that joins the moieties. The latter passes through a second-order saddle point in which the internal rotation and pericyclic reaction occur simultaneously. This path is the most energetically favorable, as the zero-point corrected energy at the saddle point structure is 0.16 kcal/mol below that of a putative (CH3)3CCOOH-SO3 precursor complex. Additional computational work involving a series of carboxylic acids is reported, which explores the effects of gas-phase acidity and basicity of the RCOOH reactant on reaction energetics. These calculations, together with prior experimental and theoretical studies of the acetic and trifluoroacetic derivatives, demonstrate that the basicity of the carbonyl oxygen, not the acidity of the COOH proton, is the important driving factor for the reaction. As a precursor to the experimental work on the title molecule, microwave spectra of the parent and OD forms of the pivalic acid monomer were recorded and are reported here as well. A convenient synthesis of SO3 is also described.

6.
Obstet Gynecol ; 139(6): 1012-1017, 2022 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-35675598

RESUMEN

Fertility-preservation counseling in the transgender patient population is recommended by multiple organizations, including the American Society for Reproductive Medicine, the World Professional Association for Transgender Health, and the Endocrine Society. The optimal time to pursue fertility preservation has not been established, and data on potential effects of testosterone therapy on future reproductive potential are limited. This Current Commentary seeks to elucidate the most appropriate time to perform oocyte cryopreservation in relation to time on and off testosterone therapy, age of the individual, and emotional effect of treatment. Although there have been multiple studies that have demonstrated successful oocyte cryopreservation regardless of testosterone exposure, the data on live-birth rates after oocyte cryopreservation are limited. Moreover, the process of oocyte cryopreservation may have a significant negative emotional effect on the transgender male given the feminizing effects of gonadotropin stimulation, as well as the invasiveness of pelvic ultrasonograms and the oocyte-retrieval procedure. With our review, we demonstrate that a comprehensive, individualized approach to fertility-preservation counseling and timing to pursue treatment are essential. Postponing fertility-preservation procedures until patients have reached early adulthood might be considered to avoid the potential effect on mental health, without compromising outcomes.


Asunto(s)
Preservación de la Fertilidad , Personas Transgénero , Adulto , Consejo , Criopreservación/métodos , Preservación de la Fertilidad/métodos , Humanos , Masculino , Recuperación del Oocito , Oocitos , Testosterona/uso terapéutico
7.
J Assist Reprod Genet ; 39(7): 1577-1582, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35731319

RESUMEN

PURPOSE: To assess telehealth services offered by reproductive endocrinology and infertility specialists and to gauge provider experiences with incorporating telehealth into their practices. METHODS: A 16-question web-based survey on use of telehealth was distributed to Society for Assisted Reproductive Technology (SART) clinics and to Society for Reproductive Endocrinology and Infertility (SREI) members. Clinic demographic data, telehealth descriptive data, and provider satisfaction with use of telehealth were assessed. Results were collected via Survey Monkey. RESULTS: A total of 1160 individuals (330 SART clinic contacts and 830 SREI members) were reached via email with an 18.6% (216) survey response rate. All respondents indicated that they offer telehealth visits. Several telehealth platforms were used, with Zoom (62.7%) and telehealth through the clinic's electronic medical record platform (34.8%) being the most common. The majority of participants (87.0%) anticipate they will offer telehealth visits after the COVID-19 pandemic. Roughly two-thirds (64.4%) of respondents anticipate fewer telehealth visits after the pandemic because of logistics, cost, and patient/provider preference. Nearly all providers are either "very satisfied" (66.2%) or "somewhat satisfied" (31.0%) with telehealth overall. CONCLUSION: Telehealth enabled safe patient-provider interactions throughout the COVID-19 pandemic. While only one-third of survey respondents offered telehealth services before the pandemic, nearly all providers express satisfaction with telehealth and anticipate they will offer telehealth services henceforth.


Asunto(s)
COVID-19 , Infertilidad , Telemedicina , COVID-19/epidemiología , Clínicas de Fertilidad , Humanos , Infertilidad/epidemiología , Infertilidad/terapia , Pandemias
8.
Aust N Z J Obstet Gynaecol ; 62(3): 349-357, 2022 06.
Artículo en Inglés | MEDLINE | ID: mdl-35293613

RESUMEN

BACKGROUND: The number of men entering obstetrics and gynaecology (Ob/Gyn) residencies and general Ob/Gyn practice is decreasing. Gender biases against their participation may affect career decisions. OBJECTIVE: This systematic review examines: (i) female patients' gender preferences and perceptions of men as Ob/Gyns and/or medical students; and (ii) the influence of gender on students' education and career decisions. SEARCH STRATEGY: We identified relevant research via PubMed using variations of three concepts in combination: Ob/Gyn care, gender bias/preference, and medical education or career. We conducted the initial review in 2018 and repeated the search in March 2021, adding additional references via citation review of included research. SELECTION CRITERIA: We restricted the review to original research from the United States between 2000-2021. DATA COLLECTION: Fifteen studies met inclusion criteria, categorised into three groups: (i) patient's gender preference for Ob/Gyns; (ii) patient's gender preference for medical students during the Ob/Gyn clerkship; and (iii) influence of gender bias on Ob/Gyn career decisions. MAIN RESULTS: Patients prioritised their physician's care attributes (eg technical skill, compassion, experience) over gender when choosing Ob/Gyns; however, provider gender was prioritised for medical students. Male medical students more commonly reported exclusion from clinical opportunities, although objective clinical exposure was like that of female counterparts. Despite perceived gender bias, male medical students reported increased Ob/Gyn interest post-clerkship; interest did not translate into residency applications. These findings are limited by study quality and heterogeneity. CONCLUSIONS: Real and perceived gender bias among female patients and male medical students in Ob/Gyn may underlie declining numbers of men entering the field.


Asunto(s)
Ginecología , Internado y Residencia , Obstetricia , Estudiantes de Medicina , Femenino , Ginecología/educación , Humanos , Masculino , Obstetricia/educación , Embarazo , Sexismo , Estados Unidos
9.
Nat Commun ; 13(1): 169, 2022 01 10.
Artículo en Inglés | MEDLINE | ID: mdl-35013281

RESUMEN

Multiplexed mRNA profiling in the spatial context provides new information enabling basic research and clinical applications. Unfortunately, existing spatial transcriptomics methods are limited due to either low multiplexing or complexity. Here, we introduce a spatialomics technology, termed Multi Omic Single-scan Assay with Integrated Combinatorial Analysis (MOSAICA), that integrates in situ labeling of mRNA and protein markers in cells or tissues with combinatorial fluorescence spectral and lifetime encoded probes, spectral and time-resolved fluorescence imaging, and machine learning-based decoding. We demonstrate MOSAICA's multiplexing scalability in detecting 10-plex targets in fixed colorectal cancer cells using combinatorial labeling of five fluorophores with facile error-detection and removal of autofluorescence. MOSAICA's analysis is strongly correlated with sequencing data (Pearson's r = 0.96) and was further benchmarked using RNAscopeTM and LGC StellarisTM. We further apply MOSAICA for multiplexed analysis of clinical melanoma Formalin-Fixed Paraffin-Embedded (FFPE) tissues. We finally demonstrate simultaneous co-detection of protein and mRNA in cancer cells.


Asunto(s)
Diagnóstico por Imagen/métodos , Melanoma/genética , ARN Mensajero/genética , Neoplasias Cutáneas/genética , Transcriptoma , Proteína BRCA1/genética , Proteína BRCA1/metabolismo , Benchmarking , Línea Celular Tumoral , Colon/metabolismo , Colon/patología , ARN Polimerasas Dirigidas por ADN/genética , ARN Polimerasas Dirigidas por ADN/metabolismo , Diagnóstico por Imagen/instrumentación , Colorantes Fluorescentes/química , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Células HEK293 , Humanos , Antígeno Ki-67/genética , Antígeno Ki-67/metabolismo , Melanoma/diagnóstico por imagen , Melanoma/metabolismo , Melanoma/patología , Microscopía Fluorescente/instrumentación , Microscopía Fluorescente/métodos , Coactivador 3 de Receptor Nuclear/genética , Coactivador 3 de Receptor Nuclear/metabolismo , ARN Mensajero/metabolismo , Neoplasias Cutáneas/diagnóstico por imagen , Neoplasias Cutáneas/metabolismo , Neoplasias Cutáneas/patología , Análisis Espacial , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismo
10.
J Chem Phys ; 155(23): 234703, 2021 Dec 21.
Artículo en Inglés | MEDLINE | ID: mdl-34937360

RESUMEN

Polymorphism is an issue troubling numerous scientific fields. A phenomenon where molecules can arrange in different orientations in a crystal lattice, polymorphism in the field of organic photovoltaic materials can dramatically change electronic properties of these materials. Rubrene is a benchmark photovoltaic material showing high carrier mobility in only one of its three polymorphs. To use rubrene in devices, it is important to quantify the polymorph distribution arising from a particular crystal growth method. However, current methods for characterizing polymorphism are either destructive or inefficient for batch scale characterization. Lattice phonon Raman spectroscopy has the ability to distinguish between polymorphs based on low frequency intermolecular vibrations. We present here the addition of microscopy to lattice phonon Raman spectroscopy, which allows us to not only characterize polymorphs efficiently and nondestructively through Raman spectroscopy but also concurrently gain information on the size and morphology of the polymorphs. We provide examples for how this technique can be used to perform large, batch scale polymorph characterization for crystals grown from solution and physical vapor transport. We end with a case study showing how Raman microscopy can be used to efficiently optimize a green crystal growth method, selecting for large orthorhombic crystals desired for rubrene electronic device applications.

11.
Chem Sci ; 12(41): 13825-13835, 2021 Oct 27.
Artículo en Inglés | MEDLINE | ID: mdl-34760168

RESUMEN

Chromophores undergoing singlet fission are promising candidates for harnessing solar energy as they can generate a pair of charge carriers by the absorption of one photon. However, photovoltaic devices employing singlet fission are still lacking practical applications due to the limitations within the existing molecules undergoing singlet fission. Chemical modifications to acenes can lead to efficient singlet fission devices, but the influence of changes to molecular structure on the rate of singlet fission is challenging to model and predict. Using femtosecond stimulated Raman spectroscopy we have previously demonstrated that the triplet separation process during singlet fission in crystalline rubrene is associated with the loss of electron density from its tetracene core. Based on this knowledge, we mined a library of new rubrene derivatives with electron withdrawing substituents that prime the molecules for efficient singlet fission, without impacting their crystal packing. Our rationally chosen crystalline chromophores exhibit significantly improved singlet fission rates. This study demonstrates the utility and strength of a structurally sensitive spectroscopic technique in providing insights to spectroscopy-guided materials selection and design guidelines that go beyond energy arguments to design new singlet fission-capable chromophores.

12.
Case Rep Womens Health ; 31: e00340, 2021 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-34336601

RESUMEN

INTRODUCTION: Cervical ectopic pregnancy (CEP) is a rare but potentially life-threatening phenomenon, and conclusive management guidelines have not been elucidated. Patients undergoing assisted reproductive technologies (ART) are at increased risk of CEP and noninvasive, fertility-sparing treatments are necessary for this population. This case report demonstrates the safety and efficacy of a single dose of intramuscular methotrexate for CEP in early gestation. CASE DESCRIPTION: A 45-year-old patient (G3P0030) presenting with painless vaginal bleeding was found to have CEP on transvaginal ultrasound at 5 weeks and 1 day of gestation after undergoing day-5 frozen embryo transfer. She was given one 50 mg/m2 dose of intramuscular methotrexate and she remained in a stable condition while being observed in the hospital. Her beta-hCG level decreased 38.2% between day 4 and day 7 after treatment and returned to nonpregnancy levels by day 28. DISCUSSION: A single dose of intramuscular methotrexate is an effective, noninvasive, fertility-sparing method of treatment for CEP in patients who are early in gestation and hemodynamically stable. This is a recommended option, especially for those undergoing fertility treatment. Further studies need to be performed to formulate national guidelines regarding the treatment of CEP.

13.
World J Mens Health ; 39(2): 172-185, 2021 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31749341

RESUMEN

Conventional semen analysis (SA) is an essential component of the male infertility workup, but requires laboratories to rigorously train and monitor technicians as well as regularly perform quality assurance assessments. Without such measures there is room for error and, consequently, unreliable results. Furthermore, clinicians often rely heavily on SA results when making diagnostic and treatment decisions, however conventional SA is only a surrogate marker of male fecundity and does not guarantee fertility. Considering these challenges, the last several decades have seen the development of many advances in SA methodology, including tests for sperm DNA fragmentation, acrosome reaction, and capacitation. While these new diagnostic tests have improved the scope of information available to clinicians, they are expensive, time-consuming, and require specialized training. The latest advance in laboratory diagnostics is the measurement of seminal oxidation-reduction potential (ORP). The measurement of ORP in an easy, reproducible manner using a new tool called the Male Infertility Oxidative Stress System (MiOXSYS) has demonstrated ORP's potential as a feasible adjunct test to conventional SA. Additionally, the measurement of ORP by this device has been shown to be predictive of both poor semen quality and male infertility. Assessing ORP is a novel approach to both validating manual SA results and identifying patients who may benefit from treatment of male oxidative stress infertility.

14.
J Clin Pharmacol ; 61(6): 755-762, 2021 06.
Artículo en Inglés | MEDLINE | ID: mdl-33314168

RESUMEN

Nearly all international regimens for pediatric acute lymphoblastic leukemia (ALL) incorporate intravenous "high-dose" methotrexate (HDMTX, ≥1 g/m2 ) to penetrate the central nervous system. Dosing is routinely adjusted for body surface area (BSA), but limited data describe the pharmacokinetics of HDMTX, particularly in obese and/or large patients. To understand the impact of body size (BSA) and body fat percentage (BFP) on HDMTX pharmacokinetics, we performed a secondary analysis of 36 children and adolescents 10-21 years old treated for newly diagnosed ALL and who were enrolled in a prospective study examining body composition. All patients received 5 g/m2 of HDMTX infused over 24 hours. Plasma methotrexate concentrations were measured at 24, 42, and 48 hours. At 48 hours, ≥0.4 µmol/L was defined as "delayed elimination," necessitating prolonged supportive care. BFP was measured using dual-energy x-ray absorptiometry. A nonparametric population pharmacokinetic model was constructed with subsequent simulations to explore effects of BSA and BFP extremes. Despite standard BSA-adjusted dosing, we found significant intrapatient variability in mean MTX concentration (38%; range, 1.2%-86%). BSA and BFP were not linearly associated with increased area under the curve (AUC, P = 0.74 and P = 0.12), but both larger size (BSA) and greater obesity (BFP) were associated with an approximately 2-fold higher risk for delayed elimination at 48 hours. HDMTX AUC was not associated with toxicity. MTX pharmacokinetics vary among and even within patients despite BSA-adjusted dosing. Obesity and large size are identified as new risk factors for delayed elimination, requiring further investigation.


Asunto(s)
Tejido Adiposo/fisiología , Antimetabolitos Antineoplásicos/farmacocinética , Metotrexato/farmacocinética , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamiento farmacológico , Adolescente , Antimetabolitos Antineoplásicos/administración & dosificación , Área Bajo la Curva , Niño , Creatinina/sangre , Relación Dosis-Respuesta a Droga , Femenino , Humanos , Masculino , Metotrexato/administración & dosificación , Modelos Biológicos , Obesidad/epidemiología , Estudios Prospectivos , Adulto Joven
15.
Fertil Steril ; 115(4): 1029-1034, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33276964

RESUMEN

OBJECTIVE: To query transgender and gender-diverse individuals on their desire for fertility preservation, perceived barriers to access care, and decisional regret. DESIGN: Cross-sectional. SETTING: Not applicable. PATIENT(S): A total of 397 gender-diverse individuals undergoing intake to the University of California Los Angeles Gender Health Program from January 2018 to March 2019. Seventy participated in a follow-up survey from September to October 2019 clarifying reproductive desires or intentions. INTERVENTION: Multiple-choice questionnaire. MAIN OUTCOME MEASURE(S): Perceived barriers to access fertility preservation and decisional regret surrounding choice to pursue fertility preservation as measured with the use of the validated Decision Regret Scale (scored 0 to 100). RESULT(S): Barriers to accessing care were primarily cost of treatment (36%), discontinuation/delay of hormonal therapy (19%), or worsening of gender dysphoria with treatment/pregnancy (11%). Respondents indicated that their family planning goals were addressed by primary care providers and/or medical endocrinologists (multiple responses allowed), but 37% stated that their family planning goals were not adequately addressed. Those who had made a firm decision to pursue or not pursue fertility treatment had mild decisional regret. Moderate-to-severe decisional regret was noted in those who were undecided regarding the pursuit of fertility perseveration before transition and in those who were interested in referral to reproductive endocrinology. CONCLUSION(S): Consultation with a reproductive endocrinologist may reduce decisional regret as well as clarify perceived barriers to fertility preservation in transgender and gender-diverse individuals interested in fertility preservation.


Asunto(s)
Toma de Decisiones/fisiología , Emociones/fisiología , Preservación de la Fertilidad/psicología , Fertilidad/fisiología , Accesibilidad a los Servicios de Salud , Personas Transgénero/psicología , Adolescente , Adulto , Estudios Transversales , Femenino , Preservación de la Fertilidad/tendencias , Estudios de Seguimiento , Accesibilidad a los Servicios de Salud/tendencias , Humanos , Masculino , Persona de Mediana Edad , Derivación y Consulta/tendencias , Adulto Joven
16.
European J Org Chem ; 2020(16): 2448-2453, 2020 May 03.
Artículo en Inglés | MEDLINE | ID: mdl-33071626

RESUMEN

The drimentine family is a class of hybrid isoprenoids derived from actinomycete bacteria. Members of this family display weak antitumor and antibacterial activity. Herein we report our efforts toward the total synthesis of drimentine C using three distinct approaches incorporating palladium-catalyzed cyanoamidation, reductive cross-coupling, and photoredox-catalyzed α-alkylation of an aldehyde as key steps. Our synthetic efforts use a convergent synthesis to assemble the terpenoid and alkaloid portions of drimentine C from readily available l-tryptophan, l-proline, and (+)-sclareolide.

17.
Org Lett ; 21(15): 6149-6154, 2019 08 02.
Artículo en Inglés | MEDLINE | ID: mdl-31339730

RESUMEN

The diazatricyclic core of the madangamine alkaloids was synthesized from a densely functionalized cyclohexane derivative. An alkene and two cyanoformamide groups are used to form two new rings and a new quaternary stereocenter in a cascade reaction, which involves two Pd-catalyzed C-C bond activation steps. The synthesis of the cascade precursor involves an intramolecular Staudinger reaction of a vicinal diester that gives a [3.2.1]azabicyclooctane derivative, allowing the regioselective introduction of a monosubstituted alkene.


Asunto(s)
Alcaloides/química , Alquenos/química , Catálisis , Ciclohexanos/química , Estereoisomerismo
18.
Chemistry ; 25(7): 1727-1732, 2019 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-30512211

RESUMEN

Alkenes can be cleaved by means of the (3+2) cycloaddition and subsequent cycloreversion of 1,3-dipoles, classically ozone (O3 ), but the azide (R-N3 ) variant is rare. Chemoselectivity for these azide to alkene diazo group transfers (DGT) is typically disfavored, thus limiting their synthetic utility. Herein, this work discloses a palladium-catalyzed intramolecular azide to alkene DGT, which grants chemoselectivity over competing aziridination. The data support a catalytic cycloreversion mechanism distinct from other known metal-catalyzed azide/alkene reactions: nitrenoid/metalloradical and (3+2) cycloadditions. Kinetics experiments reveal an unusual mechanistic profile in which the catalyst is not operative during the rate-controlling step, rather, it is active during the product-determining step. Catalytic DGT was used to synthesize N-heterocyclic quinazolinones, a medicinally relevant structural core. We also report on the competing aziridination and subsequent ring expansion to another N-heterocyclic core structure of interest, benzodiazepinones.

19.
iScience ; 2: 182-192, 2018 Apr 27.
Artículo en Inglés | MEDLINE | ID: mdl-30428374

RESUMEN

There is considerable interest in improving the performance of organic optoelectronic devices through processing techniques. Here, we study the effect of high-temperature annealing on the properties of the semiconducting polymer PTB7 and PTB7:fullerene blends, of interest as efficient organic photovoltaic (OPV) devices. Annealing to moderate temperature improves the PTB7 morphology and optoelectronic properties. High-temperature annealing also improves morphology but results in poorer optoelectronic properties. This is a result of side chain cleavage that creates by-products that act as trap states, increasing electronic disorder and decreasing mobility. We further observe changes to the PTB7 chemical structure after thermal cleavage that are similar to those following solar irradiation. This implies that side chain cleavage is an important mechanism in device photodegradation, which is a major "burn-in" loss mechanism in OPV. These results lend insight into side chain cleavage as a method of improving optoelectronic properties and suggest strategies for improvement in device photostability.

20.
J Am Chem Soc ; 140(31): 10025-10033, 2018 08 08.
Artículo en Inglés | MEDLINE | ID: mdl-29990425

RESUMEN

One major goal of organometallic chemists is the direct functionalization of the bonds most recurrent in organic molecules: C-H, C-C, C-O, and C-N. An even grander challenge is C-C bond formation when both precursors are of this category. Parallel to this is the synthetic goal of achieving reaction selectivity that contrasts with conventional methods. Electrophilic aromatic substitution (EAS) via Friedel-Crafts acylation is the most renowned method for the synthesis of aryl ketones, a common structural motif of many pharmaceuticals, agrochemicals, fragrances, dyes, and other commodity chemicals. However, an EAS synthetic strategy is only effective if the desired site for acylation is in accordance with the electronic-controlled regioselectivity of the reaction. Herein we report steric-controlled regioselective arene acylation with salicylate esters via iridium catalysis to access distinctly substituted benzophenones. Experimental and computational data indicate a unique reaction mechanism that integrates C-O activation and C-H activation with a single iridium catalyst without an exogenous oxidant or base. We disclose an extensive exploration of the synthetic scope of both the arene and the ester components, culminating in the concise synthesis of the potent anticancer agent hydroxyphenstatin.

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