Radical versus Non-Radical Reactivity in ortho- and para-Quinonedimethides and Implications for Cycloaddition Mechanisms.

The latent singlet diradical character of the parent ortho-quinonedimethide (o-QDM), as revealed by valence bond calculations, is demonstrated experimentally by trapping with the kinetically stable free radical TEMPO at room temperature. In the absence of TEMPO, the main pathway for decomposition at ambient temperature is not (as previously proposed in the literature) a radical reaction but instead a concerted Diels-Alder dimerization, which through ωB97X-D/aug-cc-pVTZ/SMD//M06-2X-D3/6-31+G(d,p)/SMD calculations is shown to proceed through an ambimodal bispericyclic transition state. The predominantly non-radical reactivity of o-QDM at room temperature differs from that of its isomeric para-quinonedimethide (p-QDM) congener, which self-reacts exclusively through radical pathways. These findings suggest the potential for tunable concerted/stepwise cycloadditions.

Plasma cell-free RNA signatures of inflammatory syndromes in children.

Inflammatory syndromes, including those caused by infection, are a major cause of hospital admissions among children and are often misdiagnosed because of a lack of advanced molecular diagnostic tools. In this study, we explored the utility of circulating cell-free RNA (cfRNA) in plasma as an analyte for the differential diagnosis and characterization of pediatric inflammatory syndromes. We profiled cfRNA in 370 plasma samples from pediatric patients with a range of inflammatory conditions, including Kawasaki disease (KD), multisystem inflammatory syndrome in children (MIS-C), viral infections, and bacterial infections. We developed machine learning models based on these cfRNA profiles, which effectively differentiated KD from MIS-C-two conditions presenting with overlapping symptoms-with high performance [test area under the curve = 0.98]. We further extended this methodology into a multiclass machine learning framework that achieved 80% accuracy in distinguishing among KD, MIS-C, viral, and bacterial infections. We further demonstrated that cfRNA profiles can be used to quantify injury to specific tissues and organs, including the liver, heart, endothelium, nervous system, and the upper respiratory tract. Overall, this study identified cfRNA as a versatile analyte for the differential diagnosis and characterization of a wide range of pediatric inflammatory syndromes.

Total Syntheses of the Tropolone-Containing Sesquiterpene Olaximbriside A and Its Decarbonylated Counterpart Olaximbriside B.

The racemic modification of the α-tropolone-containing sesquiterpene olaximbriside A [viz. (±)-4)] has been prepared over 12 steps from the readily accessible decalin derivative 12. The last two of these steps involve a fully regiocontrolled substitution reaction of bromotropone 24. The aromatization of a stereoisomeric and co-produced form of compound 12 has provided (±)-olaximbriside B [(±)-5)].

Molecular basis of inhibition of the amino acid transporter B0AT1 (SLC6A19).

The epithelial neutral amino acid transporter B0AT1 (SLC6A19) is the major transporter for the absorption of neutral amino acids in the intestine and their reabsorption in the kidney. Mouse models have demonstrated that lack of B0AT1 can normalize elevated plasma amino acids in rare disorders of amino acid metabolism such as phenylketonuria and urea-cycle disorders, implying a pharmacological approach for their treatment. Here we employ a medicinal chemistry approach to generate B0AT1 inhibitors with IC50-values of 31-90 nM. High-resolution cryo-EM structures of B0AT1 in the presence of two compounds from this series identified an allosteric binding site in the vestibule of the transporter. Mechanistically, binding of these inhibitors prevents a movement of TM1 and TM6 that is required for the transporter to make a conformational change from an outward open state to the occluded state.

Total Synthesis of a Peptide Diatom Sex Pheromone Bearing a Sulfated Aspartic Acid.

The peptide sex-inducing pheromone SIP+ (1) bearing an unusual sulfated aspartic acid residue induces sexual reproduction in diatom populations. Herein, we report the first total synthesis of SIP+ using both a sulfated building block approach and a solid-phase peptide synthesis (SPPS)-compatible late-stage sulfation strategy to assemble the natural product. The modular approaches provide concise routes to useful quantities of the natural product for future structure activity relationship studies examining the role of SIP+ in diatom biology.

Household Transmission Dynamics of Asymptomatic SARS-CoV-2-Infected Children: A Multinational, Controlled Case-Ascertained Prospective Study.

BACKGROUND: Asymptomatic SARS-CoV-2 infection in children is highly prevalent but its acute and chronic implications have been minimally described. METHODS: In this controlled case-ascertained household transmission study, we recruited asymptomatic children <18 years with SARS-CoV-2 nucleic acid testing performed at 12 tertiary care pediatric institutions in Canada and the United States. We attempted to recruit all test-positive children and 1 to 3 test-negative, site-matched controls. After 14 days' follow-up we assessed the clinical (ie, symptomatic) and combined (ie, test-positive, or symptomatic) secondary attack rates (SARs) among household contacts. Additionally, post-COVID-19 condition (PCC) was assessed in SARS-CoV-2-positive participating children after 90 days' follow-up. RESULTS: A total of 111 test-positive and 256 SARS-CoV-2 test-negative asymptomatic children were enrolled between January 2021 and April 2022. After 14 days, excluding households with co-primary cases, the clinical SAR among household contacts of SARS-CoV-2-positive and -negative index children was 10.6% (19/179; 95% CI: 6.5%-16.1%) and 2.0% (13/663; 95% CI: 1.0%-3.3%), respectively (relative risk = 5.4; 95% CI: 2.7-10.7). In households with a SARS-CoV-2-positive index child, age <5 years, being pre-symptomatic (ie, developed symptoms after test), and testing positive during Omicron and Delta circulation periods (vs earlier) were associated with increased clinical and combined SARs among household contacts. Among 77 asymptomatic SARS-CoV-2-infected children with 90-day follow-up, 6 (7.8%; 95% CI: 2.9%-16.2%) reported PCC. CONCLUSIONS: Asymptomatic SARS-CoV-2-infected children, especially those <5 years, are important contributors to household transmission, with 1 in 10 exposed household contacts developing symptomatic illness within 14 days. Asymptomatic SARS-CoV-2-infected children may develop PCC.

Plasma Cell-free RNA Signatures of Inflammatory Syndromes in Children.

Inflammatory syndromes, including those caused by infection, are a major cause of hospital admissions among children and are often misdiagnosed because of a lack of advanced molecular diagnostic tools. In this study, we explored the utility of circulating cell-free RNA (cfRNA) in plasma as an analyte for the differential diagnosis and characterization of pediatric inflammatory syndromes. We profiled cfRNA in 370 plasma samples from pediatric patients with a range of inflammatory conditions, including Kawasaki disease (KD), Multisystem Inflammatory Syndrome in Children (MIS-C), viral infections and bacterial infections. We developed machine learning models based on these cfRNA profiles, which effectively differentiated KD from MIS-C - two conditions presenting with overlapping symptoms - with high performance (Test Area Under the Curve (AUC) = 0.97). We further extended this methodology into a multiclass machine learning framework that achieved 81% accuracy in distinguishing among KD, MIS-C, viral, and bacterial infections. We further demonstrated that cfRNA profiles can be used to quantify injury to specific tissues and organs, including the liver, heart, endothelium, nervous system, and the upper respiratory tract. Overall, this study identified cfRNA as a versatile analyte for the differential diagnosis and characterization of a wide range of pediatric inflammatory syndromes.

Aluminyl derived ethene functionalization with heteroallenes, leading to an intramolecular ligand rearrangement.

The aluminacyclopropane K[Al(NON)(η-C2H4)] ([NON]2- = [O(SiMe2NDipp)2]2-, Dipp = 2,6-iPr2C6H3) reacts with CO2 and iPrNCNiPr to afford ring-expanded products of C-C bond formation. The latter system undergoes a 1,3-silyl retro-Brook rearrangement of the NON-group, to afford the [NNO]2- ligand ([NNO]2- = [N(Dipp)SiMe2N(Dipp)SiMe2O]2-). The mechanism of transformation was examined by density functional theory (DFT).

Polymers from Cellulosic Waste: Direct Polymerization of Levoglucosenone using DBU as a Catalyst.

The bio-based platform molecule levoglucosenone (LGO) is now produced at multi-ton scale by the pyrolysis of cellulosic waste. As such it has become an industrially viable, non-petroleum-derived chemical feedstock. Herein we report the direct (one-step) and operationally simple polymerization of LGO that provides a highly sustainable method for polymer synthesis. Specifically, the ability of LGO to act as an electrophile has been harnessed so as to deliver high molecular weight polymers (Mn=236,000 g/mol, D=2.4) possessing excellent thermal stabilities (TD5 %=249 °C). Furthermore, there is a significant capacity for the effective chemical manipulation of these polymers as exemplified by treatment of them under Baeyer-Villiger conditions and so creating a simple and green route to hydrophilic materials. These one- and two-step transformations provide the most direct route to new, LGO-derived polymer scaffolds yet reported. E-factors of ca. 0.012 and atom economies of up to 99 % have been realized.

A Deep Learning Framework for Image-Based Screening of Kawasaki Disease.

Kawasaki disease (KD) is a leading cause of acquired heart disease in children and is characterized by the presence of a combination of five clinical signs assessed during the physical examination. Timely treatment of intravenous immunoglobin is needed to prevent coronary artery aneurysm formation, but KD is usually diagnosed when pediatric patients are evaluated by a clinician in the emergency department days after onset. One or more of the five clinical signs usually manifests in pediatric patients prior to ED admission, presenting an opportunity for earlier intervention if families receive guidance to seek medical care as soon as clinical signs are observed along with a fever for at least five days. We present a deep learning framework for a novel screening tool to calculate the relative risk of KD by analyzing images of the five clinical signs. The framework consists of convolutional neural networks to separately calculate the risk for each clinical sign, and a new algorithm to determine what clinical sign is in an image. We achieved a mean accuracy of 90% during 10-fold cross-validation and 88% during external validation for the new algorithm. These results demonstrate the algorithms in the proposed screening tool can be utilized by families to determine if their child should be evaluated by a clinician based on the number of clinical signs consistent with KD.Clinical Relevance- This screening framework has the potential for earlier clinical evaluation and detection of KD to reduce the risk of coronary artery complications.

Impact of SARS-CoV-2 Infection on the Association Between Laboratory Tests and Severe Outcomes Among Hospitalized Children.

Background: To assist clinicians with identifying children at risk of severe outcomes, we assessed the association between laboratory findings and severe outcomes among severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected children and determined if SARS-CoV-2 test result status modified the associations. Methods: We conducted a cross-sectional analysis of participants tested for SARS-CoV-2 infection in 41 pediatric emergency departments in 10 countries. Participants were hospitalized, had laboratory testing performed, and completed 14-day follow-up. The primary objective was to assess the associations between laboratory findings and severe outcomes. The secondary objective was to determine if the SARS-CoV-2 test result modified the associations. Results: We included 1817 participants; 522 (28.7%) SARS-CoV-2 test-positive and 1295 (71.3%) test-negative. Seventy-five (14.4%) test-positive and 174 (13.4%) test-negative children experienced severe outcomes. In regression analysis, we found that among SARS-CoV-2-positive children, procalcitonin ≥0.5 ng/mL (adjusted odds ratio [aOR], 9.14; 95% CI, 2.90-28.80), ferritin >500 ng/mL (aOR, 7.95; 95% CI, 1.89-33.44), D-dimer ≥1500 ng/mL (aOR, 4.57; 95% CI, 1.12-18.68), serum glucose ≥120 mg/dL (aOR, 2.01; 95% CI, 1.06-3.81), lymphocyte count <1.0 × 109/L (aOR, 3.21; 95% CI, 1.34-7.69), and platelet count <150 × 109/L (aOR, 2.82; 95% CI, 1.31-6.07) were associated with severe outcomes. Evaluation of the interaction term revealed that a positive SARS-CoV-2 result increased the associations with severe outcomes for elevated procalcitonin, C-reactive protein (CRP), D-dimer, and for reduced lymphocyte and platelet counts. Conclusions: Specific laboratory parameters are associated with severe outcomes in SARS-CoV-2-infected children, and elevated serum procalcitonin, CRP, and D-dimer and low absolute lymphocyte and platelet counts were more strongly associated with severe outcomes in children testing positive compared with those testing negative.

A Rapid Aza-Bicycle Synthesis from Dendralenes and Imines.

The diene-transmissive 2-fold Diels-Alder sequence between carbon-based dienophiles and [3]dendralenes is becoming an established method for polycarbocycle synthesis. Here, we demonstrate for the first time that imines are competent participants in intermolecular formal [4 + 2] cycloadditions with dendralenes. After a second Diels-Alder process with a carbadienophile, hexahydro- and octahydro-isoquinoline structures are formed. The formal aza-Diels-Alder reaction, which requires Lewis acid promotion, proceeds in high regio- and stereoselectivity under optimized conditions. ωB97XD/Def2-TZVP//M06-2X/6-31+G(d,p) calculations reveal a stepwise ionic mechanism for the formal aza-dienophile cycloadditions and also explain an unexpected Z → E olefin isomerization of a non-reacting C═C bond in the first formal cycloaddition.

Computational and Experimental Confirmation of the Diradical Character of para-Quinonedimethide.

The ground-state structure of the parent para-quinonedimethide (p-QDM) molecule is generally represented in its closed shell form, i.e., as a cyclic, nonaromatic, through-conjugated/cross-conjugated hybrid comprising four C═C bonds. Nonetheless, p-QDM has been theorized to contain a contribution from its open-shell aromatic singlet diradical form. VBSCF calculations identify an open-shell contribution of 29% to the structure, while CASPT2(16,16)/def2-TZVP and ωB97XD/aug-cc-pVTZ calculations predict that dimerization proceeds along an open-shell singlet diradical pathway with a low (77 kJ/mol) barrier toward dimerization, which occurs by way of C-C bond formation between the exocyclic methylene carbons. A similar low (98 kJ/mol) barrier exists toward the reaction between a p-QDM molecule and the radical trap TEMPO. These predictions are verified experimentally through the isolation of bis-TEMPO-trapped p-QDM, its C-C coupled dimer, and by demonstrating that a mixture of p-QDM and TEMPO can initiate the radical polymerization of n-butyl acrylate at ambient temperature. In contrast to p-QDM, tetracyanoquinone (TCNQ) neither dimerizes nor reacts with TEMPO, despite having a similar diradical character to p-QDM. This lack of reactivity is consistent with both a higher kinetic barrier and a thermodynamically unfavorable process, which is ascribed to destabilizing steric clashes and polar effects.

Synthesis and Atropisomeric Properties of Benzoazepine-Fused Isoindoles.

Atropisomeric, bench-stable benzoazepine-fused isoindoles were synthesized via oxidation from isoindoline precursors. Using the isoindoles 5d-f as models, the stereochemistry and conformational folding of the systems were examined. Chiral UHPLC was used to analyze the rate of racemization and calculate the Gibbs free energy of enantiomerization (ΔG‡Enant). X-ray crystallography, 1H NMR spectroscopy, and DFT calculations were used to elucidate the three axes of chirality and clarify the structural factors contributing to ΔG‡Enant. Tandem rotation around the axes of chirality precludes the formation of diastereomers, with rotational restriction of the Caryl-Nsulfonamide bond determined as the moderator of atropisomeric stability in the system, affected primarily by steric hindrance as well as by π-stacking interactions facilitated by the folded conformation of the sulfonamide over the isoindole moiety.

Palladium-catalysed enantio- and regioselective (3 + 2) cycloaddition reactions of sulfamidate imine-derived 1-azadienes towards spirocyclic cyclopentanes.

An enantio- and diastereoselective Pd-catalysed (3 + 2) cycloaddition of bis(trifluoroethyl) 2-vinyl-cyclopropane-1,1-dicarboxylate (VCP) with cyclic sulfamidate imine-derived 1-azadienes (SDAs) has been developed. These reactions provide highly functionalized spiroheterocycles having three contiguous stereocentres, including a tetrasubstituted carbon bearing an oxygen functionality. The two geminal trifluoroethyl ester moieties can be manipulated in a facially selective manner to afford more diversely decorated spirocycles with four contiguous stereocentres. In addition, diastereoselective reduction of the imine moiety can also afford a fourth stereocentre and exposes the important 1,2-amino alcohol functionality.

Amino Acid Sulfinate Salts as Alkyl Radical Precursors.

A general approach to the synthesis of amino acid sulfinate salts from commercially available α-chiral hydroxylated amino acids is reported. These reagents are shown to be valuable precursors to alkyl radicals under mild photochemical oxidation conditions. The photochemically generated amino acid radicals engage readily with alkyl and aryl disulfide radical traps to afford a diverse suite of modified amino acids.

Predictive Factors for Delayed Surgical Intervention in Children With Epidural Hematomas.

BACKGROUND: Optimal treatment of children with traumatic intracranial epidural hematomas (EDHs) is unknown. We sought to identify clinical and radiographic predictors of delayed surgical intervention among children with EDH admitted for observation. METHODS: We retrospectively identified patients younger than 15 years with acute traumatic EDHs evaluated at our level 1 pediatric trauma center. We excluded patients with penetrating head injuries, recent surgical evacuation of EDH, or depressed skull fracture requiring surgical repair and assigned the remaining subjects to the immediate surgery group if they underwent immediate surgical evacuation, to the supportive-therapy-only group if they underwent observation only, and to the delayed surgery group if they underwent surgery after observation. We abstracted clinical and laboratory findings, surgical interventions, and neurological outcome and measured EDH dimensions and volumes, adjusting for cranial size. We compared clinical and radiographic characteristics among groups and performed receiver-operator characteristic analyses of predictors of delayed surgery. RESULTS: Of 172 patients with EDH, 103 patients met the inclusion criteria, with 6 (6%) in the immediate surgery group, 87 (84%) in the supportive-therapy-only group, and 10 (10%) in the delayed surgery group. Headache, prothrombin time of >14 seconds, EDH maximal thickness of ≥1.1 cm, volume of ≥14 mL, EDH thickness/cranial width index of ≥0.08 and EDH volume/cranial volume index of ≥0.18, and mass effect were associated with delayed surgical intervention. There was no difference in length of stay or functional impairment between the immediate and delayed surgery groups. However, patients in delayed surgery group were more likely to have subjective symptoms at discharge than those in immediate surgery group. CONCLUSIONS: Among patients with EDH admitted for observation, larger EDH, mass effect, headaches, and prothrombin time of >14 seconds were associated with delayed surgical intervention. A larger-scale study is warranted to identify independent predictors of delayed surgery in children under observation for EDH.

Divergent reactivity of usnic acid and evaluation of its derivatives for antiproliferative activity against cancer cells.

Natural products continue to be an inspiration for new drugs to treat debilitating diseases such as cancer. Usnic acid is a secondary metabolite isolated predominately from lichen species and has been shown to exhibit antiproliferative properties, however its application is limited by poor drug-like properties and low specificity. We report our work on investigating the reactivity of usnic acid for incorporating heterocyclic rings and the divergent reactivity that can be obtained by simply altering the reaction solvent and temperature. The synthesised derivatives were then tested against HeLa cancer cells for their antiproliferative properties. A number of promising compounds were obtained including 4, 5 and 9 that showed an IC50 of 878, 311 and 116 nM, respectively, against HeLa cancer cells after 48 h of treatment.

The in vivo metabolism of Jungle Warfare in greyhounds.

Δ6-Methyltestosterone was reported as the main active ingredient of the purported "dietary supplement" Jungle Warfare. This compound is structurally similar to 17α-methyltestosterone, containing an additional Δ6 double bond, and is reported to possess notable androgenic activity, raising concerns over the potential for abuse of Jungle Warfare in sport. The in vivo metabolism of Δ6-methyltestosterone in greyhounds was investigated. Urinary phase I (unconjugated) and phase II (glucuronide) metabolites were detected following oral administration using liquid chromatography-mass spectrometry. No phase II sulfate metabolites were detected. The major phase I metabolite was confirmed as 16α,17ß-dihydroxy-17α-methylandrosta-4,6-dien-3-one by comparison with a synthetically-derived reference material. Minor amounts of the parent drug were also confirmed. Glucuronide conjugated metabolites were also observed, but were found to be resistant to hydrolysis using the Escherichia coli ß-glucuronidase enzyme. Qualitative excretion profiles, limits of detection, and extraction recoveries were determined for the parent drug and the major phase I metabolite. These results provide a method for the detection of Jungle Warfare abuse in greyhounds suitable for incorporation into routine screening methods conducted by anti-doping laboratories.