Pd(II)/diphosphine/curcumin complexes as potential anticancer agents.

Palladium(II) complexes have stimulated research interest mainly due to their in vitro cytotoxicity against various cancer cell lines and their low cytotoxicity in healthy cells. Thus, in this work, we combined Pd(II)/phosphine systems with the natural product curcumin as a ligand, obtaining a series of complexes, [Pd(cur)(PPh3)2]PF6 (A1), [Pd(cur)(dppe)]PF6 (A2), [Pd(cur)(dppp)]PF6 (A3), [Pd(cur)(dppb)]PF6 (A4) and [Pd(cur)(dppf)]PF6 (A5), where dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, and dppf = 1,1'-bis(diphenylphosphino)ferrocene (P-P), which were characterized by elemental analysis, molar conductivity analysis, and mass, NMR (1H, 13C, 31P{1H}), UV-vis, and IR spectroscopies, and four of them (A1, A2, A4, and A5) by X-ray crystallography. The in vitro cell viability of the complexes A1-A5, cisplatin, and the free ligand curcumin against MDA-MB-231 (human triple-negative breast tumor cells), SK-BR-3 (human breast tumor cells), A549 (human lung tumor cells), MRC-5 (non-tumor human lung cells), A2780 (human ovarian carcinoma cells), and A2780cis (cisplatin-resistant human ovarian carcinoma cells), was evaluated by the MTT colorimetric assay. For the tumor cell lines tested, the complexes showed good anticancer activities. The results showed that in general the complexes had lower IC50 values than free curcumin and the precursors [PdCl2(P-P)]. IC50 results obtained for the A1-A5 complexes, in the MCF-7 cell line, are similar to those that had already been observed for some Pd/bipy/curcumin complexes. In the MDA-MB-231 cell line, complexes A1 and A5 stood out, with their lowest IC50 values, around 5 µmol L-1, and the complexes appeared to be more active (lower IC50 values) against the ovarian cell lines. Complex A1 was 23 and 22-fold more cytotoxic than cisplatin, against the A2780 and A2780cis cells, respectively. The complex A1 was studied on A2780cis cells and it was found that this complex inhibits colony formation and induces cell cycle arrest in the sub-G1 phase in a concentration-dependent manner and leads to cell death by apoptosis. The DCFDA assay revealed a potent ROS induction for complex A1.

Continuous flow reactions in the preparation of active pharmaceutical ingredients and fine chemicals.

Herein, we present an overview of continuous flow chemistry, including photoflow and electroflow technologies in the preparation of active pharmaceutical ingredients (APIs) and fine chemical intermediates. Examples highlighting the benefits and challenges associated with continuous flow processes, mainly involving continuous thermal, photo- and electrochemical transformations, are drawn from the relevant literature, especially our experience and collaborations in this area, with emphasis on the synthesis and prospective scale-up.

Synergic vascular photodynamic activity by methylene blue-curcumin supramolecular assembly.

A supramolecular assembly was obtained by combining methylene blue (MB) with a natural plant extract, curcumin (Curc), in a stoichiometric ratio of 1:4 in aqueous solution (90% PBS + 10% ethanol) at room temperature. The MB-Curc supramolecular assembly was evidenced by absorption and fluorescence spectroscopies, and the stoichiometry and bonding constant were obtained using Cielens model. Its stability and photostability were evaluated by chromatographic analysis and UV-Vis absorption. The MB-Curc avoids the aggregation of both isolated compounds and efficiently produces singlet oxygen (ΦΔ= 0.52 ± 0.03). Its potential for photodynamic antiangiogenic treatments was evaluated through the vascular effect observed in chicken chorioallantoic membrane (CAM) assay. The results showed intense damage in CAM vascular network by MB-Curc after irradiation, which is higher than the effect of isolated compounds, indicating a synergistic vascular effect. This combination can be essential to prevent cancer revascularization after photodynamic application and improve the efficacy of this approach. The characteristics exhibited by MB-Curc make it a potential candidate for use in cancer treatments through photodynamic antiangiogenic therapy.

Synthesis of the Brivaracetam Employing Asymmetric Photocatalysis and Continuous Flow Conditions.

An original total synthesis of the antiepileptic drug brivaracetam (BRV) is reported. The key step in the synthesis consists of an enantioselective photochemical Giese addition, promoted by visible-light and the chiral bifunctional photocatalyst Δ-RhS. Continuous flow conditions were employed to improve the efficiency and allow an easy scale-up of the enantioselective photochemical reaction step. The intermediate obtained from the photochemical step was converted into BRV by two different pathways, followed by one alkylation and amidation, thus giving the desired active pharmaceutical ingredients (API) in 44% overall yield, 9:1 diastereoisomeric ratio (dr) and >99:1 enantiomeric ratio (er).

Electrochemical reduction of 5-benzylidene thiazolidine-2,4-diones: a greener approach to the preparation of glitazone APIs.

A transition-metal free methodology for the chemoselective reduction of benzylidene thiazolidine-2,4-diones and similar heterocycles is described, allowing the preparation of a broad scope of the corresponding reduced derivatives in up to 90% yield. The protocol has a simple and safe experimental setup, in which water was employed as the hydrogen source. To further demonstrate the synthetic utility of this transformation, the antidiabetic API Pioglitazone was prepared in 81% yield. To the best of our knowledge, this is the first hydride and transition-metal free protocol for the synthesis of Pioglitazone, highlighting its potential utility as a greener alternative in both academic and industrial synthesis.

Recent Advances in the Multistep Continuous Preparation of APIs and Fine Chemicals.

Over the last two decades, with the advent of continuous flow technologies, continuous processes have emerged as a major area in organic synthesis. In this context, continuous flow processes have been increasing in the preparation of Active Pharmaceutical Ingredients (APIs) and fine chemicals, such as complex synthetic intermediates, agrochemicals, and fragrances. Thus, the development of multi-step protocols has attracted special interest from the academic and industrial chemistry communities. In addition to the beneficial aspects intrinsically associated with continuous processes (e.g., waste reduction, optimal heat transfer, improved safety, and the possibility to work under harsh reaction conditions and with more dangerous reagents), these protocols also allow a rapid increase in molecular complexity. Moreover, in telescoped multi-step processes, isolation and purification steps are generally avoided or, if necessary, carried out in-line, presenting an important economy of time, solvents, reagents, and labor. Last, important synthetic strategies such as photochemical and electrochemical reactions are compatible with flow processes and are delivering relevant advances to the synthetic approaches. In this review, a general overview of the fundamentals of continuous flow processes is presented. Recent examples of multi-step continuous processes for the preparation of fine chemicals, including telescoped and end-to-end processes, are discussed, pointing out the possible advantages and/or limitations of each of these methodologies.

Multicomponent Reactions Applied to Total Synthesis of Biologically Active Molecules: A Short Review.

Multicomponent reactions (MCRs) are processes in which three or more starting materials are combined in the same reaction vessel, forming an adduct that contains all or most of the atoms of the starting materials. MCRs are one-pot processes that provide attractive advantages for the total synthesis of target molecules. These reactions allow rapid access to structurally complex adducts from particularly simple starting materials. Moreover, MCRs are generally intrinsically associated with principles of green syntheses, such as atom economy, minimization of isolation, and purification of synthetic intermediates, leading to large solvent economies and avoiding the production of large amounts of reaction waste. Thus, synthetic routes employing multicomponent reactions are generally more convergent, economical and often allow higher overall yields. In total synthesis, the use of MCRs has been mainly applied in the preparation of key advanced intermediates. Progress in the use of MCRs in total synthesis has been described over the last decades, including not only classical MCRs reactions (e.g. isocyanide-based transformations), but also non-traditional multicomponent reactions. Furthermore, reports concerning stereoselective multicomponent transformations are still scarce and present further development opportunities. This review aims to provide a general overview of the application of MCRs as key steps in the rapid preparation of structurally complex derivatives and fine chemicals. In special, some selected examples have been successfully applied for medicinal purposes. Finally, in some representative cases, either key intermediates formed during the reaction vessel or corresponding transition states have been disclosed in order to provide insights into the reaction mechanisms.

Concise two-step chemical synthesis of molnupiravir.

A concise synthesis of molnupiravir in a one-pot two-step approach starting from uridine is described. Formally, herein, two sets of one-pot two-reaction steps introducing simplicity for purifications and using chemically available reagents are presented. In this context, molnupiravir was obtained in up to 68% overall yield and multigram-scale. In addition, HPLC analysis showed the molnupiravir purity above 99%.

Synthesis of Fentanyl under Continuous Photoflow Conditions.

An advantageous and original synthesis of fentanyl is described. This new approach includes two efficient continuous flow reductive aminations achieved via photoredox catalysis and a final batch acylation. A telescoped protocol for the two photocatalyzed steps is also presented, and overall, this protocol provides improved sustainability, significant efficiency, reduced temperatures and reaction times, and is functional for scaling up this relevant active pharmaceutical ingredient (API).

Dual role of benzophenone enables a fast and scalable C-4 selective alkylation of pyridines in flow.

The efficient C-4 selective modification of pyridines is a major challenge for the synthetic community. Current strategies are plagued with at least one drawback regarding functional group-tolerant electronic activation of the heteroarene, mild generation of the required alkyl radicals, regioselectivity, safety and/or scalability. Herein, we describe a fast, safe and scalable flow process which allows preparation of said C-4 alkylated pyridines. The process involves a photochemical hydrogen atom transfer (HAT) event to generate the carbon-centered radicals needed to alkylate the C-2 blocked pyridine. In a two-step streamlined flow process, this light-mediated alkylation step is combined with a nearly instantaneous inline removal of the blocking group. Notably, cheap benzophenone plays a dual role in the pyridine alkylation mechanism by activating the hydrocarbon feedstock reagents via a HAT mechanism, and by acting as a benign, terminal oxidant. The key role of benzophenone in the operative reaction mechanism has also been revealed through a combination of experimental and computational studies.

Environmentally Safe Photodynamic Control of Aedes aegypti Using Sunlight-Activated Synthetic Curcumin: Photodegradation, Aquatic Ecotoxicity, and Field Trial.

This study reports curcumin as an efficient photolarvicide against Aedes aegypti larvae under natural light illumination. Larval mortality and pupal formation were monitored daily for 21 days under simulated field conditions. In a sucrose-containing formulation, a lethal time 50 (LT50) of 3 days was found using curcumin at 4.6 mg L-1. This formulation promoted no larval toxicity in the absence of illumination, and sucrose alone did not induce larval phototoxicity. The photodegradation byproducts (intermediates) of curcumin were determined and the photodegradation mechanisms proposed. Intermediates with m/z 194, 278, and 370 were found and characterized using LC-MS. The ecotoxicity of the byproducts on non-target organisms (Daphnia, fish, and green algae) indicates that the intermediates do not exhibit any destructive potential for aquatic organisms. The results of photodegradation and ecotoxicity suggest that curcumin is environmentally safe for non-target organisms and, therefore, can be considered for population control of Ae. aegypti.

Visible-Light-Promoted Synthesis of 1,3-Dicarbonyl Sulfoxonium Ylides.

A novel visible-light-promoted coupling of diazoketones with sulfoxonium ylides, employing a violet light-emitting diode, is described under both batch and continuous flow conditions. This transformation permits the direct synthesis of synthetically useful 1,3-dicarbonyl sulfoxonium ylides (33 examples, 21-85% yields), by means of an acylation from the in situ and selective generation of ketenes. The reaction performed under flow conditions proved to be very efficient, providing the 1,3-dicarbonyl sulfoxonium ylides with higher yields and shorter reaction times.

Scaled up and telescoped synthesis of propofol under continuous-flow conditions.

Herein we report a machine-assisted and scaled-up synthesis of propofol, a short-acting drug used in procedural sedation, which is extensively in demand during this COVID-19 pandemic. The continuous-flow protocol proved to be efficient, with great potential for industrial translation, reaching a production up to 71.6 g per day with process intensification (24 h-continuous experiments). We have successfully telescoped a continuous flow approach obtaining 5.74 g of propofol with productivity of 23.0 g/day (6 h-continuous experiment), proving the robustness of the method in both separated and telescoped modes. Substantial progress was also achieved for the in-line workup, which provides greater safety and less waste, also relevant for industrial application. Overall, the synthetic strategy is based on the Friedel-Crafts di-isopropylation of low-cost p-hydroxybenzoic acid, followed by a decarboxylation reaction, giving propofol in up to 84% overall yield and very low by-product formation. The continuous flow synthesis of propofol 3 is presented as a two-step protocol. The isopropylated intermediate 2 was obtained from 4-hydroxybenzoic acid (1) in up 43.8 g, 85% yield and 30 min residence time. Propofol 3 was then obtained in 71.6 g, 87% yield, and 16 min residence time. A safe and cost-competitive machine-assisted protocol is described with a process intensification demonstration (24 h experiments) and a telescoped process intensification (6 h).

Direct Synthesis of α-Sulfenylated Ketones under Electrochemical Conditions.

We investigated the electrochemical sulfenylation reaction in both batch and continuous flow regimes, involving thiophenols/thiols and enol-acetates to yield α-sulfenylated ketones, without using additional oxidants or catalysts. Studies with different electrolytes were also performed, revealing that quaternary ammonium salts are the best mediators for this reaction. Notably, during the study of the reaction scope, a Boc-cysteine proved to be extremely tolerant to our protocol, thus increasing its relevance. The methodology also proved to be scalable in both batch and continuous flow conditions, opening up possibilities for further studies since these relevant functional groups are important moieties in organic synthesis.

Photochemical α-Aminonitrile Synthesis Using Zn-Phthalocyanines as Near-Infrared Photocatalysts.

While photochemical transformations with sunlight almost exclusively utilize the UV-vis part of the solar spectrum, the majority of the photons emitted by the sun have frequencies in the near-infrared region. Phthalocyanines show high structural similarity to the naturally occurring light-harvesting porphyrins, chlorins, and mainly bacteriochlorins and are also known for being efficient and affordable near-infrared light absorbers as well as triplet sensitizers for the production of singlet oxygen. Although having been neglected for a long time in synthetic organic chemistry due to their low solubility and high tendency toward aggregation, their unique photophysical properties and chemical robustness make phthalocyanines attractive photocatalysts for the application in near-infrared-light-driven synthesis strategies. Herein, we report a cheap, simple, and efficient photocatalytic protocol, which is easily scalable under continuous-flow conditions. Various phthalocyanines were studied as near-infrared photosensitizers in oxidative cyanations of tertiary amines to generate α-aminonitriles, a synthetically versatile compound class.

Formulations of curcumin and d-mannitol as a photolarvicide against Aedes aegypti larvae: Sublethal photolarvicidal action, toxicity, residual evaluation, and small-scale field trial.

Dengue, Zika, chikungunya, and yellow fever are arboviruses transmitted by Aedes aegypti mosquito. In this regard, a number of techniques have emerged aiming to combat its proliferation. Elimination of Aedes aegypti larvae by photodynamic action has been reported as an efficient approach. In this regard, this study was aimed at synthetize and characterize formulations with different proportions (w/w) of the plant-based photolarvicidal curcumin and d-mannitol (CCD 1-4) and their evaluation on sublethal photolarvicidal efficiency, photodegradation profile,solubility, internalization, elimination time, persistence in simulated field, growth of microorganisms in water and the toxicity using an animal models (Zebrafish). CCD 3 (curcumin:d-mannitol 50:50 w/w) showed the best efficacy (LC50-24h = 0.01 mg/L), and also presented the shortest internalization and longest elimination time, 60 min and 8 days, respectively. This formulation caused an extrusion into the intestine and peritrophic membrane. Moreover, CCD 3 showed a photodegradation of 50% (in 24 h) under white fluorescent lamps. In a small-scale field trial, CCD 3 had a residual time of 14 days and abnormal microbial growth was not observed. Finally, CCD 3 did not present any toxicity in Zebrafish, after exposition for 24 h at 100 mg/L. Overall, these results raise the possibility of reducing virus transmission through the controlled photoinactivation of Aedes aegypti larvae using a non-toxic plant-based formulated photolarvicide.

Metabolizable Protein: 2. Requirements for Maintenance in Growing Saanen Goats.

This study aimed to estimate the protein requirements for the maintenance of growing Saanen goats of different sexes from 5 to 45 kg of body weight (BW) using two methods and applying a meta-analysis. For this purpose, two datasets were used. One dataset was used to evaluate the effects of sex on the protein requirements for maintenance using the comparative slaughter technique. This dataset was composed of 185 individual records (80 intact males, 62 castrated males, and 43 females) from six studies. The other dataset was used to evaluate the effects of sex on the protein requirements for maintenance using the N balance method. This dataset was composed of 136 individual records (59 intact males, 43 castrated males, and 34 females) from six studies. All studies applied an experimental design that provided different levels of N intake and different levels of N retention, allowing the development of regression equations to predict the net protein requirement for maintenance (NPM) and the metabolizable protein (MP) requirements for maintenance (MPM) in Saanen goats. The efficiency of MP use for maintenance (kPM) was computed as NPM/MPM. The efficiency of MP use for gain (kPG) was calculated using the equation of daily protein retained against daily MP intake above maintenance. A meta-analysis was applied using the MIXED procedure of SAS, in which sex was considered a fixed effect, and blocks nested in the studies and goat sex were considered as random effects. The NPM did not differ between sexes, irrespective of the approach used. The daily NPM estimated was 1.23 g/kg0.75 BW when using the comparative slaughter technique, while it was 3.18 g/kg0.75 BW when using the N balance technique for growing Saanen goats. The MPM estimated was 3.8 g/kg0.75 BW, the kPM was 0.33, and the kPG was 0.52. We observed that the NPM when using the comparative slaughter technique in growing Saanen goats is lower than that recommended by the current small ruminant feeding systems; on the other hand, the MPM was similar to previous reports by the feeding systems. Sex did not affect the protein requirements for maintenance and the efficiencies of use of metabolizable protein.

Synthesis of multi-substituted pyridines from ylidenemalononitriles and their emission properties.

Numerous methodologies to obtain pyridines from ylidenemalononitriles are described in the literature. Nevertheless, they are limited to the use of microwave or conventional heat and few lead to 2,3,4 or 2,3,4,5-substituted pyridines as multi-proposal molecular scaffolds or even universal pyridines. Herein, we present a mild and facile solvent-free methodology to obtain a scope of multi-substituted pyridines at room temperature. We also report an example where one of the resulting amino-nicotinonitriles exhibits a preliminary evidence of aggregation-induced emission (AIE).

Electron-Donor-Acceptor Complex-Enabled Flow Methodology for the Hydrotrifluoromethylation of Unsaturated ß-Keto Esters.

A novel electron-donor-acceptor (EDA) complex-enabled flow photochemical hydrotrifluoromethylation of unsaturated ß-keto esters is described. The developed protocol has an easy experimental procedure and does not require the use of transition-metal-based photocatalysts, allowing the isolation of 14 new compounds in up to 86% yield. Control experiments and computational studies revealed that the reaction proceeds through a Michael-type 1,4-addition of a trifluoromethyl radical, followed by a proton transfer step. Furthermore, the reaction could be scaled up to 1 mmol, and the final product could be employed in the preparation of an isoxazolone and a pyrazolone as trifluoro-substituted heterocycles.

Alterations in the mechanical, chemical and biocompatibility properties of low-cost polyethylene and polyester meshes after steam sterilization.

INTRODUCTION: In Africa and other Low Resource Settings (LRS), the guideline-based and thus in most cases mesh-based treatment of inguinal hernias is only feasible to a very limited extent. This has led to an increased use of low cost meshes (LCMs, mostly mosquito meshes) for patients in LRS. Most of the LCMs used are made of polyethylene or polyester, which must be sterilized before use. The aim of our investigations was to determine changes in the biocompatibility of fibroblasts as well as mechanical and chemical properties of LCMs after steam sterilization. MATERIAL AND METHODS: Two large-pored LCMs made of polyester and polyethylene in a size of 11 x 6 cm were cut and steam sterilized at 100, 121 and 134 °C. These probes and non-sterile meshes were then subjected to mechanical tensile tests in vertical and horizontal tension, chemical analyses and biocompatibility tests with human fibroblasts. All meshes were examined by stereomicroscopy, scanning electron microscopy (SEM), LDH (cytotoxicity) measurement, viability testing, pH, lactate and glycolysis determination. RESULTS: Even macroscopically, polyethylene LCMs showed massive shrinkage after steam sterilization, especially at 121 and 134 °C. While polyester meshes showed no significant changes after sterilization with regard to deformation and damage as well as tensile force and stiffness, only the unsterile polyethylene mesh and the mesh sterilized at 100 °C could be tested mechanically due to the shrinkage of the other specimen. For these meshes the tensile forces were about four times higher than for polyester LCMs. Chemical analysis showed that the typical melting point of polyester LCMs was between 254 and 269 °C. Contrary to the specifications, the polyethylene LCM did not consist of low-density polyethylene, but rather high-density polyethylene and therefore had a melting point of 137 °C, so that the marked shrinkage described above occurred. Stereomicroscopy confirmed the shrinkage of polyethylene LCMs already after sterilization at 100 °C in contrast to polyester LCMs. Surprisingly, cytotoxicity (LDH measurement) was lowest for both non-sterile LCMs, while polyethylene LCMs sterilized at 100 and 121 °C in particular showed a significant increase in cytotoxicity 48 hours after incubation with fibroblasts. Glucose metabolism showed no significant changes between sterile and non-sterile polyethylene and polyester LCMs. CONCLUSION: The process of steam sterilization significantly alters mechanical and structural properties of synthetic hernia mesh implants. Our findings do not support a use of low-cost meshes because of their unpredictable properties after steam sterilization.