Structural Investigation of Technetium Dibutylphosphate Species Using X-ray Absorption Fine Structure Spectroscopy.

The speciation of Tc after the extraction of Tc(IV) from H2O and 1 M HNO3 by dibutylphosphoric acid (HDBP) in dodecane has been studied by X-ray absorption fine structure (XAFS) spectroscopy. Results show the formation of dimeric species with Tc2O2 and Tc2O units, and the formulas [Tc2O2(DBP·HDBP)4] (1) and [Tc2O(NO3)2(DBP)2(DBP·HDBP)2] (2) were, respectively, proposed for the species extracted from H2O and 1 M HNO3. The interatomic Tc-Tc distances found in the Tc2O2 and Tc2O units [2.55(3) and 3.57(4) Å, respectively] are similar to the ones found in Tc(IV) dinuclear species. It is likely that the speciation of Tc(IV) in dodecane is due to the extraction of a species with a Tc2O unit for (2) and to the redissolution of a Tc(IV)-DBP solid for (1). The XAFS results for (1) and (2) were compared to that obtained for the extraction of Tc(IV) with TBP/HDBP/dodecane from 0.5 M HNO3, (3) which highlight the formation of Tc mononuclear nitrate species {i.e., [Tc(NO3)3(DBP)] or [Tc(NO3)2(DBP·HDBP)]}. These results confirm the importance of the preparation and speciation of the Tc(IV) aqueous solutions prior to extraction and how much this influences and drives the final Tc speciation in organic extraction. These studies outline the complexity of Tc separation chemistry and provide insights into the behavior of Tc during the reprocessing of used nuclear fuel.

Structural Basis of Stereospecific Vanadium-Dependent Haloperoxidase Family Enzymes in Napyradiomycin Biosynthesis.

Vanadium-dependent haloperoxidases (VHPOs) from Streptomyces bacteria differ from their counterparts in fungi, macroalgae, and other bacteria by catalyzing organohalogenating reactions with strict regiochemical and stereochemical control. While this group of enzymes collectively uses hydrogen peroxide to oxidize halides for incorporation into electron-rich organic molecules, the mechanism for the controlled transfer of highly reactive chloronium ions in the biosynthesis of napyradiomycin and merochlorin antibiotics sets the Streptomyces vanadium-dependent chloroperoxidases apart. Here we report high-resolution crystal structures of two homologous VHPO family members associated with napyradiomycin biosynthesis, NapH1 and NapH3, that catalyze distinctive chemical reactions in the construction of meroterpenoid natural products. The structures, combined with site-directed mutagenesis and intact protein mass spectrometry studies, afforded a mechanistic model for the asymmetric alkene and arene chlorination reactions catalyzed by NapH1 and the isomerase activity catalyzed by NapH3. A key lysine residue in NapH1 situated between the coordinated vanadate and the putative substrate binding pocket was shown to be essential for catalysis. This observation suggested the involvement of the ε-NH2, possibly through formation of a transient chloramine, as the chlorinating species much as proposed in structurally distinct flavin-dependent halogenases. Unexpectedly, NapH3 is modified post-translationally by phosphorylation of an active site His (τ-pHis) consistent with its repurposed halogenation-independent, α-hydroxyketone isomerase activity. These structural studies deepen our understanding of the mechanistic underpinnings of VHPO enzymes and their evolution as enantioselective biocatalysts.

Total Synthesis of Atrachinenins A and B.

Inspired by a new biosynthetic hypothesis, we report a biomimetic total synthesis of atrachinenins A and B that explains their racemic nature. The synthesis exploits an intermolecular Diels-Alder reaction between a quinone meroterpenoid and E-ß-ocimene, followed by intramolecular (3 + 2) cycloaddition and a late-stage aerobic oxidation. Divergent transformations of a simple model system gave several complex polycyclic scaffolds, while also suggesting a structure revision for atrachinenin C.

Biomimetic Dearomatization Strategies in the Total Synthesis of Meroterpenoid Natural Products.

Natural products are biosynthesized from a limited pool of starting materials via pathways that obey the same chemical logic as textbook organic reactions. Given the structure of a natural product, it is therefore often possible to predict its likely biosynthesis. Although biosynthesis mainly occurs in the highly specific chemical environments of enzymes, the field of biomimetic total synthesis attempts to replicate predisposed pathways using chemical reagents.We have followed several guidelines in our biomimetic approach to total synthesis. The overarching aim is to construct the same skeletal C-C and C-heteroatom bonds and in the same order as our biosynthetic hypothesis. In order to explore the innate reactivity of (bio)synthetic intermediates, the use of protecting groups is avoided or at least minimized. The key step, which is usually a cascade reaction, should be predisposed to selectively generate molecular complexity under substrate control (e.g., cycloadditions, radical cyclizations, carbocation rearrangements). In general, simple reagents and mild conditions are used; many of the total syntheses presented in this Account could be achieved using pre-1980s methodology. We have focused almost exclusively on the synthesis of meroterpenoids, that is, natural products of mixed terpene and aromatic polyketide origin, using commercially available terpenes and electron-rich aromatic compounds as starting materials. Finally, all of the syntheses in this Account involve a dearomatization step as a means to trigger a cascade reaction or to construct stereochemical complexity from a planar, aromatic intermediate.A biomimetic strategy can offer several advantages to a total synthesis project. Most obviously, successful biomimetic syntheses are usually concise and efficient, naturally adhering to the atom, step, and redox economies of synthesis. For example, in this Account, we describe a four-step synthesis of garcibracteatone and a three-step synthesis of nyingchinoid A. It is difficult to imagine shorter, non-biomimetic syntheses of these intricate molecules. Furthermore, biomimetic synthesis gives insight into biosynthesis by revealing the chemical relationships between biosynthetic intermediates. Access to these natural substrates allows collaboration with biochemists to help uncover the function of newly discovered enzymes and elucidate biosynthetic pathways, as demonstrated in our work on the napyradiomycin family. Third, by making biosynthetic connections between natural products, we can sometimes highlight incorrect structural assignments, and herein we discuss structure revisions of siphonodictyal B, rasumatranin D, and furoerioaustralasine. Last, biomimetic synthesis motivates the prediction of "undiscovered natural products" (i.e., missing links in biosynthesis), which inspired the isolation of prenylbruceol A and isobruceol.

Biomimetic synthesis of the non-canonical PPAP natural products yezo'otogirin C and hypermogin D, and studies towards the synthesis of norascyronone A.

Oxidative degradation and rearrangement of polycyclic polyprenylated acylphloroglucinols (PPAPs) has created diverse families of unique natural products that are attractive targets for biomimetic synthesis. Herein, we report a racemic synthesis of hyperibrin A and its oxidative radical cyclization to give yezo'otogirin C, followed by epoxidation and House-Meinwald rearrangement to give hypermogin D. We also investigated the biomimetic synthesis of norascyronone A via a similar radical cyclization pathway, with unexpected results that give insight into its biosynthesis.

Adjuvant therapy improves survival in pT4aN0 oral cavity squamous cell carcinoma with bone invasion.

OBJECTIVE: The prognostic significance of bone invasion in oral cavity squamous cell carcinoma (OCSCC) after accounting for tumor size, nodal spread, and surgical margins is controversial. The aim of this study is to determine whether patients with pT4aN0 oral cavity squamous cell carcinoma with bone invasion have improved overall and disease-free survival with adjuvant treatment. METHODS: We conducted a retrospective review of medical records from 64 patients with stage pT4aN0 due to mandibular involvement who underwent surgery from 2000 to 2020. Kaplan-Meier analysis compared disease-free survival and overall survival between groups who underwent surgery only versus surgery and adjuvant therapy. The prognostic impact of adjuvant therapy was assessed using multivariate analysis and reported as hazard ratios. RESULTS: There were no statistically significant differences in clinicopathologic features or mean follow-up between patients who received surgery only and patients who received surgery with RT/CCRT (radiotherapy/concurrent chemoradiation therapy). 5-year disease-free (42.5% versus 65.9%, p = 0.02) and overall survival (43.6% versus 69.0%, p = 0.014) were improved in groups who received surgery and RT/CCRT. Regression analysis controlling for clinicopathologic characteristics, including tumor size, identified radiation as an independent predictor of improved disease-free survival (HR: 0.04, p < 0.001) and overall survival (HR: 0.10, p < 0.001). CONCLUSION: Adjuvant RT/CCRT in patients with pT4N0 OCSCC with mandibular bone involvement is associated with improved disease-free and overall survival. This association was significant regardless of tumor pathologic features such as size or margin status. These findings may help guide physicians in counseling patients regarding risks and benefits of adjuvant RT/CCRT and inform practice guidelines.

Intramolecular Tricarbonyl-Ene Reactions and α-Hydroxy-ß-Diketone Rearrangements Inspired by the Biosynthesis of Polycyclic Polyprenylated Acylphloroglucinols.

Structurally unique natural products pose biosynthetic puzzles whose solution can inspire new chemical reactions. Herein, we propose a unified biosynthetic pathway towards some complex meroterpenoids-the hyperireflexolides, biyoulactones, hybeanones and hypermonones. This hypothesis led to the discovery of uncatalyzed, intramolecular carbonyl-ene reactions that are spontaneous at room temperature. We also developed an anionic cascade reaction featuring an α-hydroxy-ß-diketone rearrangement and an intramolecular aldol reaction to access four distinct natural product scaffolds from a common intermediate.

Bioinspired Total Synthesis of Erectones A and B, and the Revised Structure of Hyperelodione D.

The field of biomimetic synthesis seeks to apply biosynthetic hypotheses to the efficient construction of complex natural products. This approach can also guide the revision of incorrectly assigned structures. Herein, we describe the evolution of a concise total synthesis and structural reassignment of hyperelodione D, a tetracyclic meroterpenoid derived from a Hypericum plant, alongside some biogenetically related natural products, erectones A and B. The key step in the synthesis of hyperelodione D forms six stereocentres and three rings in a bioinspired cascade reaction that features an intermolecular Diels-Alder reaction, an intramolecular Prins reaction and a terminating cycloetherification.

Real-Time PCR and Droplet Digital PCR Are Accurate and Reliable Methods To Quantify Pseudomonas syringae pv. actinidiae Biovar 3 in Kiwifruit Infected Plantlets.

Pseudomonas syringae pv. actinidiae is the etiological agent of kiwifruit canker disease, causing severe economic losses in kiwifruit production areas around the world. Rapid diagnosis, understanding of bacterial virulence, and rate of infection in kiwifruit cultivars are important in applying effective measures of disease control. P. syringae pv. actinidiae load in kiwifruit is currently determined by a labor-intense colony counting method with no high-throughput and specific quantification method being validated. In this work, we used three alternative P. syringae pv. actinidiae quantification methods in two infected kiwifruit cultivars: start of growth time, quantitative PCR (qPCR), and droplet digital PCR (ddPCR). Method performance in each case was compared with the colony counting method. Methods were validated using calibration curves obtained with serial dilutions of P. syringae pv. actinidiae biovar 3 (Psa3) inoculum and standard growth curves obtained from kiwifruit samples infected with Psa3 inoculum. All three alternative methods showed high correlation (r > 0.85) with the colony counting method. qPCR and ddPCR were very specific, sensitive (5 × 102 CFU/cm2), highly correlated to each other (r = 0.955), and flexible, allowing for sample storage. The inclusion of a kiwifruit biomass marker increased the methods' accuracy. The qPCR method was efficient and allowed for high-throughput processing, and the ddPCR method showed highly accurate results but was more expensive and time consuming. While not ideal for high-throughput processing, ddPCR was useful in developing accurate standard curves for the qPCR method. The combination of the two methods is high-throughput, specific for Psa3 quantification, and useful for research studies (e.g., disease phenotyping and host-pathogen interactions).

Radiation treatment planning study to investigate feasibility of delivering Immunotherapy in Combination with Ablative Radiosurgery to Ultra-High DoSes (ICARUS).

PURPOSE: Immune checkpoint inhibitors improve survival in metastatic diseases for some cancers. Multisite SBRT with pembrolizumab (SBRT + Pembro) was shown to be safe with promising local control using biologically effective doses (BEDs) = 95-120 Gy. Increased BED may improve response rate; however, SBRT doses are limited by surrounding organs at risk (OARs). The purpose of this work was to develop and validate methods for safe delivery of ultra-high doses of radiation (BED10  > 300) to be used in future clinical trials. METHODS AND MATERIALS: The radiation plans from 15 patients enrolled on a phase I trial of SBRT + pembro were reanalyzed. Metastatic disease sites included liver (8/15), inguinal region (1/15), pelvis (2/15), lung (1/15), abdomen (1/15), spleen (1/15), and groin (1/15). Gross tumor volumes (GTVs) ranged from 80 to 708 cc. Following the same methodology used in the Phase I trial on which these patients were treated, GTVs > 65 cc were contracted to a 65 cc subvolume (SubGTV) resulting in only a portion of the GTV receiving prescription dose. Volumetric modulated arc therapy (VMAT) was used to plan treatments BED10  = 360 Gy. Plans utilizing both 6FFF and 10FFF beams were compared to clinical plans delivering BED10  = 112.50 Gy. The target primary goal was V100% > 95% with a secondary goal of V70% > 99% and OAR objectives per the trial. To demonstrate feasibility, plans were delivered to a diode array phantom and evaluated for fidelity using gamma analysis. RESULTS: All 30 plans met the secondary coverage goal and satisfied all OAR constraints. The primary goal was achieved in 12/15 of the 6FFF plans and 13/15 of the 10FFF plans. Average gamma analysis passing rate using criteria of 3% dose difference and 3, 2, and 1 mm were 99.1  ±  1.0%, 98.5  ±  1.6%, and 95.1  ±  3.8%, respectively. CONCLUSION: Novel VMAT planning approaches with clinical treatment planning software and linear accelerators prove capable of delivering radiation doses in excess of 360 Gy BED10 to tumor subvolumes, while maintaining safe OAR doses.

Patient-Reported Outcomes of Split-Thickness Skin Grafts for Floor of Mouth Cancer Reconstruction.

INTRODUCTION: Patient-reported outcome measures (PROM) on quality of life (QOL) for early-stage floor of mouth carcinoma (FOM-CA) undergoing surgical resection and split-thickness skin graft (STSG) reconstruction have not been established. We have performed a cross-sectional QOL analysis of such patients to define functional postoperative outcomes. METHODS: Patients with pathologic stage T1/T2 FOM-CA who underwent resection and STSG reconstruction at a tertiary academic cancer center reported outcomes with the University of Washington QOL (v4) questionnaire after at least 6 months since surgery. RESULTS: Twenty-four out of 49 eligible patients completed questionnaires with a mean follow-up of 41 months (range: 6-88). Subsites of tumor involvement/resection included the following: (1) lateral FOM (L-FOM) (n = 17), (2) anterior FOM (A-FOM) (n = 4), and (3) alveolar ridge with FOM, all of whom underwent lateral marginal mandibulectomy (MM-FOM) (n = 3). All patients reported swallowing scores of 70 ("I cannot swallow certain solid foods") or better. Ninety-six percent (23/24) reported speech of 70 ("difficulty saying some words, but I can be understood over the phone") or better. A-FOM patients reported worse chewing than L-FOM patients (mean: 50.0 vs. 85.3; p = 0.01). All 4 A-FOM patients reported a low chewing score of 50 ("I can eat soft solids but cannot chew some foods"). Otherwise, there were no significant differences between subsite groups in swallowing, speech, or taste. CONCLUSION: STSG reconstructions for pathologic T1-T2 FOM-CA appear to result in acceptable PROM QOL outcomes with the exception of A-FOM tumors having worse chewing outcomes.

Meroterpenoid natural products from Streptomyces bacteria - the evolution of chemoenzymatic syntheses.

Covering: Up to January 2020Meroterpenoids derived from the polyketide 1,3,6,8-tetrahydroxynaphthalene (THN) are complex natural products produced exclusively by Streptomyces bacteria. These antibacterial compounds include the napyradiomycins, merochlorins, marinones, and furaquinocins and have inspired many attempts at their chemical synthesis. In this review, we highlight the role played by biosynthetic studies in the stimulation of biomimetic and, ultimately, chemoenzymatic total syntheses of these natural products. In particular, the application of genome mining techniques to marine Streptomyces bacteria led to the discovery of unique prenyltransferase and vanadium-dependent haloperoxidase enzymes that can be used as highly selective biocatalysts in fully enzymatic total syntheses, thus overcoming the limitations of purely chemical reagents.

Total Synthesis of Rhodonoids A, B, E, and F, Enabled by Singlet Oxygen Ene Reactions.

Singlet oxygen is a versatile reagent for the selective oxidation of organic compounds under mild reaction conditions. It is frequently invoked in biosynthetic pathways, so it is especially suitable for application in the biomimetic synthesis of natural products. Herein, we show that use of the singlet oxygen ene reaction, combined with [2 + 2] cycloadditions, leads to concise, divergent, and redox-economic total syntheses of several polycyclic members of the rhodonoid family of meroterpenoids.

Biomimetic Synthetic Studies on the Bruceol Family of Meroterpenoid Natural Products.

A biomimetic approach to total synthesis can offer several benefits, including the development of cascade reactions for the rapid generation of molecular complexity, and guidance in the structure revision of old natural products and the anticipation of new ones. Herein, we describe how a biomimetic synthesis of bruceol, a pentacyclic meroterpenoid, led to the anticipation, isolation, and synthesis of isobruceol. The key step in the synthesis of both bruceol and isobruceol was an intramolecular hetero-Diels-Alder reaction of an o-quinone methide that was formed by dearomatization of an electron-rich chromene. The synthesis of an elusive biosynthetic intermediate also allowed a concise synthesis of eriobrucinol via a photochemical [2 + 2] cycloaddition. Furthermore, some speculation on the biosynthesis of prenylated bruceol derivatives inspired the development of a Claisen/Cope/Diels-Alder cascade reaction. We also report the generation of halogenated bruceol derivatives and the synthesis of several protobruceol natural products using singlet oxygen ene reactions.

Crystal and Electronic Structures of A2NaIO6 Periodate Double Perovskites (A = Sr, Ca, Ba): Candidate Wasteforms for I-129 Immobilization.

The synthesis, structure, and thermal stability of the periodate double perovskites A2NaIO6 (A= Ba, Sr, Ca) were investigated in the context of potential application for the immobilization of radioiodine. A combination of X-ray diffraction and neutron diffraction, Raman spectroscopy, and DFT simulations were applied to determine accurate crystal structures of these compounds and understand their relative stability. The compounds were found to exhibit rock-salt ordering of Na and I on the perovskite B-site; Ba2NaIO6 was found to adopt the Fm-3m aristotype structure, whereas Sr2NaIO6 and Ca2NaIO6 adopt the P21/n hettotype structure, characterized by cooperative octahedral tilting. DFT simulations determined the Fm-3m and P21/n structures of Ba2NaIO6 to be energetically degenerate at room temperature, whereas diffraction and spectroscopy data evidence only the presence of the Fm-3m phase at room temperature, which may imply an incipient phase transition for this compound. The periodate double perovskites were found to exhibit remarkable thermal stability, with Ba2NaIO6 only decomposing above 1050 °C in air, which is apparently the highest recorded decomposition temperature so far recorded for any iodine bearing compound. As such, these compounds offer some potential for application in the immobilization of iodine-129, from nuclear fuel reprocessing, with an iodine incorporation rate of 25-40 wt%. The synthesis of these compounds, elaborated here, is also compatible with both current conventional and future advanced processes for iodine recovery from the dissolver off-gas.

Isolation and Biomimetic Oxidation of Prenylbruceol A, an Anticipated Meroterpenoid Natural Product from Philotheca myoporoides.

Reinvestigation of the coumarin meroterpenoids of Philotheca myoporoides using pressurized hot water extraction (PHWE) procedures led to the isolation of prenylbruceol A, a proposed biosynthetic precursor of seven previously reported bruceol derivatives, prenylbruceols B-H. Protobruceol-I, ostruthin, dipetalactone, and a new dihydrocoumarin natural product were isolated alongside prenylbruceol A. A biomimetic singlet oxygen ene reaction of prenylbruceol A allowed the semisynthesis of prenylbruceols B, C, and D.

Neuromorphic photonics with electro-absorption modulators.

Photonic neural networks benefit from both the high-channel capacity and the wave nature of light acting as an effective weighting mechanism through linear optics. Incorporating a nonlinear activation function by using active integrated photonic components allows neural networks with multiple layers to be built monolithically, eliminating the need for energy and latency costs due to external conversion. Interferometer-based modulators, while popular in communications, have been shown to require more area than absorption-based modulators, resulting in a reduced neural network density. Here, we develop a model for absorption modulators in an electro-optic fully connected neural network, including noise, and compare the network's performance with the activation functions produced intrinsically by five types of absorption modulators. Our results show the quantum well absorption modulator-based electro-optic neuron has the best performance allowing for 96% prediction accuracy with 1.7×10-12 J/MAC excluding laser power when performing MNIST classification in a 2 hidden layer feed-forward photonic neural network.

Biomimetic synthetic studies on meroterpenoids from the marine sponge Aka coralliphaga: Divergent total syntheses of siphonodictyal B, liphagal and corallidictyals A-D.

The marine sponge Aka coralliphaga is a rich source of biologically active and structurally interesting meroterpenoids. Inspired by these natural products, we have used biosynthetic speculation to devise biomimetic syntheses of siphonodictyal B, liphagal and corallidictyals A-D from sclareolide. This work resulted in the development of new cascade reactions in the synthesis of liphagal, the reassignment of the structure of siphonodictyal B, and the realisation that corallidictyals A and B are possibly isolation artefacts.

Visible-Light Photoredox Catalysis Enables the Biomimetic Synthesis of Nyingchinoids†A, B, and D, and Rasumatranin†D.

The total synthesis of nyingchinoids A and B has been achieved through successive rearrangements of a 1,2-dioxane intermediate that was assembled using a visible-light photoredox-catalysed aerobic [2+2+2] cycloaddition. Nyingchinoid D was synthesised with a competing [2+2] cycloaddition. Based on NMR data and biosynthetic speculation, we proposed a structure revision of the related natural product rasumatranin D, which was confirmed through total synthesis. Under photoredox conditions, we observed the conversion of a cyclobutane into a 1,2-dioxane through retro-[2+2] cycloaddition followed by aerobic [2+2+2] cycloaddition.

Biomimetic and Biocatalytic Synthesis of Bruceol.

The first total synthesis of bruceol has been achieved using a biomimetic cascade cyclization initiated by a stereoselective Jacobsen-Katsuki epoxidation (and kinetic resolution) of racemic protobruceol-I. A bacterial cytochrome P450 monooxygenase was also found to catalyze the conversion of protobruceol-I into bruceol. The first full analysis of the NMR data of natural bruceol suggested that "isobruceol" was a previously unrecognized natural product also isolated from Philotheca brucei. This was confirmed by the re-isolation, synthesis, and X-ray analysis of isobruceol. In total, eight stereoisomers and structural isomers of bruceol have been synthesized in a highly divergent approach.