Efficient and controllably selective preparation of esters using uronium-based coupling agents

Oligonucleotide Catabolism-Derived Gluconucleosides in Caenorhabditis elegans

Nucleosides are essential cornerstones of life, and nucleoside derivatives and synthetic analogues have important biomedical applications. Correspondingly, production of non-canonical nucleoside derivatives in animal model systems is of particular interest. Here, we report the discovery of diverse glucose-based nucleosides in Caenorhabditis elegans and related nematodes. Using a mass spectrometric screen based on all-ion fragmentation in combination with total synthesis, we show that C. elegans selectively glucosylates a series of modified purines but not the canonical purine and pyrimidine bases. Analogous to ribonucleosides, the resulting gluconucleosides exist as phosphorylated and non-phosphorylated forms. The phosphorylated gluconucleosides can be additionally decorated with diverse acyl moieties from amino acid catabolism. Syntheses of representative variants, facilitated by a novel 2'-O- to 3'-O-dibenzyl phosphoryl transesterification reaction, demonstrated selective incorporation of different nucleobases and acyl moieties. Using stable-isotope labeling, we further show that gluconucleosides incorporate modified nucleobases derived from RNA and possibly DNA breakdown, revealing extensive recycling of oligonucleotide catabolites. Gluconucleosides are conserved in other nematodes, and biosynthesis of specific subsets is increased in germline mutants and during aging. Bioassays indicate that gluconucleosides may function in stress response pathways.

Cellulose cross-linking with folic acid at room via diverse-based coupling reagents attaining multifunctional features

Here, cellulose was cross-linked with folic acid (FA) using tetrafluoroborate (TBTU) and carbodiimide (DIC) as coupling reagents through the pad method at room temperature. The interactions between FA and cellulose were proposed and determined with FTIR, and UV-visible also confirmed with nitrogen content. The newly formed ester peak showed the grafting of FA to the cellulose through esterification followed by cellulose cross-linking. The surface morphology of treated fabrics indicated no significant changes and also remained similar after 5 washing cycles. This had no negative impacts on the various physical and mechanical fabric features. The fabric color was changed with reasonable fastness to laundering and light. More FA showed higher N content indicating more bacterial killing for Pseudomonas aeroginosa (Psa) and Methicillin-Resistant Staphylococcus (MRSA). The reasonable viability of L929 and MCF-7 cells showed for treated fabric with FA below 5 %.

N-Acetyl-l-phenylalanine Racemization during TBTU Amidation: An In-Depth Study for the Synthesis of Anti-Inflammatory 2-(N-Acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA)

A thorough study on the amidation conditions of N-acetyl-l-phenylalanine using TBTU and various bases is reported for the synthesis of 2-(N-acetyl)-l-phenylalanylamido-2-deoxy-d-glucose (NAPA), a promising drug for the treatment of joints diseases. TBTU-mediated diastereoselective amidation reaction with 1,3,4,6-tetra-O-acetyl-β-d-glucosamine always gave racemization of N-acetyl-l-phenylalanine. The stereochemical retention under amidation conditions was studied in detail in the presence of difference bases and via other control experiments, evidencing the possibility to reduce racemization using pyridine as base.

Lipid A Mimetics Based on Unnatural Disaccharide Scaffold as Potent TLR4 Agonists for Prospective Immunotherapeutics and Adjuvants

TLR4 is a key pattern recognition receptor that can sense pathogen- and danger- associated molecular patterns to activate the downstream signaling pathways which results in the upregulation of transcription factors and expression of interferons and cytokines to mediate protective pro-inflammatory responses involved in immune defense. Bacterial lipid A is the primary TLR4 ligand with very complex, species-specific, and barely predictable structure-activity relationships. Given that therapeutic targeting of TLR4 is an emerging tool for management of a variety of human diseases, the development of novel TLR4 activating biomolecules other than lipid A is of vast importance. We report on design, chemical synthesis and immunobiology of novel glycan-based lipid A-mimicking molecules that can activate human and murine TLR4-mediated signaling with picomolar affinity. Exploiting crystal structure - based design we have created novel disaccharide lipid A mimetics (DLAMs) where the inherently flexible β(1→6)-linked diglucosamine backbone of lipid A is exchanged with a conformationally restrained non-reducing βGlcN(1↔1')βGlcN scaffold. Excellent stereoselectivity in a challenging β,β-1,1' glycosylation was achieved by tuning the reactivities of donor and acceptor molecules using protective group manipulation strategy. Divergent streamlined synthesis of β,β-1,1'-linked diglucosamine-derived glycolipids entailing multiple long-chain (R)-3- acyloxyacyl residues and up two three phosphate groups was developed. Specific 3D-molecular shape and conformational rigidity of unnatural β,β-1,1'-linked diglucosamine combined with carefully optimized phosphorylation and acylation pattern ensured efficient induction of the TLR4-mediated signaling in a species-independent manner.

Outside-in strategy for peptide-based methacrylate and methacrylamide zwitterionic cross-linkers

Polyampholyte hydrogels have shown promise as functional biomaterial platforms with resistance to nonspecific protein adsorption (non-biofouling). Yet there are few zwitterionic cross-linkers available to complement these materials and provide an extended charge density throughout the 3D network. Recent development of a peptide-based zwitterionic cross-linker has shown merit. Indeed, the use of functionalizable amino acids allows for a series of peptide-based zwitterionic methacrylate and methacrylamide cross-linkers. Methacrylate additions prior to peptide coupling provides an “outside-in” strategy when using natural L-Serine or L-Lysine as substrates to produce a series of methacrylate and methacrylamide combinations and expand the library of peptide-based cross-linkers. Herein such dipeptide combinations include Ser-Lys; Lys-Ser and Lys-Lys zwitterionic bis(methacrylate/methacrylamide) cross-linkers. Highlighting the utility of the method, and potential to increase the distance between zwitterionic components, the syntheses of tripeptide Lys-Gly-Lys dimethacrylamide and Ser-Gly-Ser dimethacrylate are also shown.

From the banal to the bizarre: unravelling immune recognition and response to microbial lipids

Microbes produce a rich array of lipidic species that through their location in the cell wall and ability to mingle with host lipids represent a privileged class of immune-active molecules. Lipid-sensing immunity recognizes microbial lipids from pathogens and commensals causing immune responses. Yet microbial lipids are often heterogeneous, in limited supply and in some cases their structures are incompletely defined. Total synthesis can assist in structural determination, overcome supply issues, and provide access to high-purity, homogeneous samples and analogues. This account highlights synthetic approaches to lipidic species from pathogenic and commensal bacteria and fungi that have supported immunological studies involving lipid sensing through the pattern recognition receptor Mincle and cell-mediated immunity through the CD1-T cell axis.

Acetylation of alcohols and amines under visible light irradiation: diacetyl as an acylation reagent and photosensitizer

An unprecedented strategy for the acetylation of alcohols and amines using diacetyl as both an acylation reagent and a photosensitizer was well developed.

Total Synthesis and Bioactivity Mapping of Geodiamolide H

The first total synthesis of the actin-stabilizing marine natural product geodiamolide H was achieved. Solid-phase based peptide assembly paired with scalable stereoselective syntheses of polyketide building blocks and an optimized esterification set the stage for investigating the key ring-closing metathesis. Geodiamolide H and synthetic analogues were characterized for their toxicity and for antiproliferative effects in cellulo, by characterising actin polymerization induction in vitro, and by docking on the F-actin target and property computation in silico, for a better understanding of structure-activity relationships (SAR). A non-natural analogue of geodiamolide H was discovered to be most potent in the series, suggesting significant potential for tool compound design.

Emerging Applications of Nanotechnology in Healthcare Systems: Grand Challenges and Perspectives

Healthcare, as a basic human right, has often become the focus of the development of innovative technologies. Technological progress has significantly contributed to the provision of high-quality, on-time, acceptable, and affordable healthcare. Advancements in nanoscience have led to the emergence of a new generation of nanostructures. Each of them has a unique set of properties that account for their astonishing applications. Since its inception, nanotechnology has continuously affected healthcare and has exerted a tremendous influence on its transformation, contributing to better outcomes. In the last two decades, the world has seen nanotechnology taking steps towards its omnipresence and the process has been accelerated by extensive research in various healthcare sectors. The inclusion of nanotechnology and its allied nanocarriers/nanosystems in medicine is known as nanomedicine, a field that has brought about numerous benefits in disease prevention, diagnosis, and treatment. Various nanosystems have been found to be better candidates for theranostic purposes, in contrast to conventional ones. This review paper will shed light on medically significant nanosystems, as well as their applications and limitations in areas such as gene therapy, targeted drug delivery, and in the treatment of cancer and various genetic diseases. Although nanotechnology holds immense potential, it is yet to be exploited. More efforts need to be directed to overcome these limitations and make full use of its potential in order to revolutionize the healthcare sector in near future.

Synthesis of a zwitterionic N-Ser-Ser-C dimethacrylate cross-linker and evaluation in polyampholyte hydrogels

Polyampholyte hydrogels are attractive materials for tissue engineering scaffolds as they offer a wide variety of features including nonfouling, selective protein delivery, and tunable physical characteristics. However, to improve the potential performance of these materials for in vivo applications, there is a need for a higher diversity of zwitterionic cross-linker species to replace commonly used ethylene glycol (EG) based chemistries. Towards this end, the synthesis of a dipeptide based zwitterionic cross-linker, N-Ser-Ser-C dimethacrylate (S-S) from N-Boc-l-serine is presented. The strategy utilized a convergent coupling of methacrylated serine partners followed by careful global deprotection to yield the zwitterionic cross-linker with good overall yields. This novel cross-linker was incorporated into a polyampholyte hydrogel and its physical properties and biocompatibility were compared against a polyampholyte hydrogel synthesized with an EG-based cross-linker. The S-S cross-linked hydrogel demonstrated excellent nonfouling performance, while promoting enhanced cellular adhesion to fibrinogen delivered from the hydrogel. Therefore, the results suggest that the S-S cross-linker will demonstrate superior future performance for in vivo applications.

Self-assembly of diclofenac prodrug into nanomicelles for enhancing the anti-inflammatory activity

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely prescribed for the treatment of various types of inflammatory conditions. Diclofenac is a very common NSAID that is utilized to relieve pain and reduce fever and, most importantly, inflammation. However, it suffers from low water solubility and a low dissolution profile. Therefore, we aim to develop a new drug delivery system based on the synthesis of amphiphilic structures that are capable of self assembling into nano-micelles which will be a water-soluble delivery system for the diclofenac. The amphiphilic structure consists of a hydrophilic moiety of triethylene glycol (TEG), polyethylene glycol PEG 400, or PEG 600 linked with the hydrophobic drug diclofenac through an ester linkage. The diclofenac derivatives were successfully synthesized as confirmed by nuclear magnetic resonance. Moreover, the formation of the micellar structure of the synthesized amphiphilic derivatives was confirmed by atomic force microscopy obtaining a spherical shape of the micelles with average diameters of 200 nm for Dic-PEG400-Dic, and 110 nm for Dic-PEG600-Dic. The critical micelle concentration has been determined as 2.7 × 10^-3 mg mL^-1 for Dic-PEG400-Dic, and 1 × 10^-4 mg mL^-1 for Dic-PEG600-Dic. The in vitro diclofenac release profile by esterase enzyme was conducted and showed almost complete conversion to free diclofenac within 35 h in the case of Dic-PEG400-Dic micelles and more than 85% of Dic-PEG600-Dic micelles. Then the anti-inflammatory activity was determined by testing the TNF-α production in LPS-stimulated Balb/c mice. Diclofenac micelles significantly suppressed TNF-α production after a 5 mg kg^-1 dose was given. The developed micelles showed TNF-α inhibition up to 87.4% and 84% after 48 hours of treatment in the case of Dic-PEG400-Dic and Dic-PEG600-Dic micelles respectively in comparison to 42.3% in the case of diclofenac alone. Dic-PEG400-Dic micelles showed the most potent anti-inflammatory activity with improved TNF-α suppression through time progress. Therefore, the developed nano-micelles provide a facile synthetic approach to enhance diclofenac water solubility, improve the anti-inflammatory effect and achieve a sustained release profile to get better patient compliance.

Systemic Immunotherapy with Micellar Resiquimod-Polymer Conjugates Triggers a Robust Antitumor Response in a Breast Cancer Model

Resiquimod is an immunopotent toll-like receptor 7/8 agonist with antitumor activity. Despite being potent against skin cancers, it is poorly tolerated systemically due to toxicity. Integrating resiquimod into nanoparticles presents an avenue to circumvent the toxicity problem. Herein, the preparation of degradable nanoparticles with covalently bound resiquimod and their systemic application in cancer immunotherapy is reported. Dispersion in water of amphiphilic constructs integrating resiquimod covalently bound via degradable amide or ester linkages yields immune-activating nanoparticles. The degradable agonist-nanoparticle bonds allow the release of resiquimod from the carrier nanoparticles. In vitro assays with antigen presenting cells demonstrate that the nanoparticles retain the immunostimulatory activity of resiquimod. Systemic administration of the nanoparticles and checkpoint blockade (aPD-1) to a breast cancer mouse model with multiple established tumors triggers antitumor activity evidenced by suppressed tumor growth and enhanced CD8+ T-cell infiltration. Nanoparticles with ester links, which hydrolyze more readily, yield a stronger immune response with 75% of tumors eliminated when combined with aPD-1. The reduced tumor growth and the presence of activated CD8+ T-cells across multiple tumors suggest the potential for treating metastatic cancer.

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones

This work reviews the contributions of the corresponding author (M.M.M.P.) and her research group to Medicinal Chemistry concerning the isolation from plant and marine sources of xanthone derivatives as well as their synthesis, biological/pharmacological activities, formulation and analytical applications. Although her group activity has been spread over several chemical families with relevance in Medicinal Chemistry, the main focus of the investigation and research has been in the xanthone family. Xanthone derivatives have a variety of activities with great potential for therapeutic applications due to their versatile framework. The group has contributed with several libraries of xanthones derivatives, with a variety of activities such as antitumor, anticoagulant, antiplatelet, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective, antioxidant, and multidrug resistance reversal effects. Besides therapeutic applications, our group has also developed xanthone derivatives with analytical applications as chiral selectors for liquid chromatography and for maritime application as antifouling agents for marine paints. Chemically, it has been challenging to afford green chemistry methods and achieve enantiomeric purity of chiral derivatives. In this review, the structures of the most significant compounds will be presented.

Photocatalytic amidation and esterification with perfluoroalkyl iodide

Effect of excited-state properties and mechanistic study on visible-light induced photocatalytic amidation and esterification with perfluoroalkyl halides under mild conditions.

Toward the Identification of Novel Antimicrobial Agents: One-Pot Synthesis of Lipophilic Conjugates of N-Alkyl d- and l-Iminosugars

In the effort to improve the antimicrobial activity of iminosugars, we report the synthesis of lipophilic iminosugars 10a-b and 11a-b based on the one-pot conjugation of both enantiomeric forms of N-butyldeoxynojirimycin (NBDNJ) and N-nonyloxypentyldeoxynojirimycin (NPDNJ) with cholesterol and a succinic acid model linker. The conjugation reaction was tuned using the established PS-TPP/I2/ImH activating system, which provided the desired compounds in high yields (94-96%) by a one-pot procedure. The substantial increase in the lipophilicity of 10a-b and 11a-b is supposed to improve internalization within the bacterial cell, thereby potentially leading to enhanced antimicrobial properties. However, assays are currently hampered by solubility problems; therefore, alternative administration strategies will need to be devised.

OxymaPure Coupling Reagents: Beyond Solid-Phase Peptide Synthesis

OxymaPure [ethyl 2-cyano-2-(hydroxyimino)acetate] is an exceptional reagent with which to suppress racemization and enhance coupling efficiency during amide bond formation. The tremendous popularity of OxymaPure has led to the development of several Oxyma-based reagents. OxymaPure and its derived reagents are widely used in solid- and solution-phase peptide chemistry. This review summarizes the recent developments and applications of OxymaPure and Oxyma-based reagents in peptide chemistry, in particular in solution-phase chemistry. Moreover, the side reaction associated with OxymaPure is also discussed.

1 Introduction

2 Oxyma-Based Coupling Reagents

2.1 Aminium/Uronium Salts of OxymaPure

2.2 Phosphonium Salts of OxymaPure

2.3 Oxyma-Based Phosphates

2.4 Sulfonate Esters of OxymaPure

2.5 Benzoate Esters of OxymaPure

2.6 Carbonates of OxymaPure Derivatives

3 OxymaPure Derivatives

4 Other Oxime-Based Additives and Coupling Reagents

5 Side Reactions Using OxymaPure Derivatives

6 Conclusion

7 List of Abbreviations

Design of potent Mincle signalling agonists based on an alkyl β-glucoside template

The innate immune receptor Mincle senses lipid-based molecules derived from pathogens, commensals and altered self. Based on emerging structure-activity relationships we design simple alkyl 6-O-acyl-β-d-glucosides that are effective agonists of Mincle and signal with potency on par with the prototypical ligand trehalose dimycolate.

H-Phosphonate Synthesis and Biological Evaluation of an Immunomodulatory Phosphoglycolipid from Thermophilic Bacteria

The synthesis of a library of bacterial phosphoglycolipid, PGL-1, is described. Key features of the synthesis include regioselective esterification of the primary alcohol of the diacylglycerol moiety and an H-phosphonate method to install the phosphate in PGL-1 in comparison with earlier reported procedures. A representative set of PGL-1 analogues was prepared and evaluated for their biological activities. Results showed that the immunological activity of PGL-1 is dependent on the chain lengths of the fatty acids.

Polymer-Bound Triphenylphosphine and 4,4'-Dinitroazobenzene as a Coupling Reagents for Chromatography-Free Esterification Reaction

AIM AND OBJECTIVE

Sustainable production of fine chemicals both in industries and pharmaceuticals heavily depends on the application of solid-phase synthesis route coupled with microwave technologies due to their environmentally benign nature. In this report, a microwave-assisted esterification reaction using polymer-bound triphenylphosphine and 4,4'-dinitroazobenzene reagent system was investigated.

MATERIALS AND METHODS

The solvents were obtained from Merck India. Polymer-bound triphenylphosphine (~3 mmol triphenylphosphine moiety/g) was acquired from Sigma-Aldrich. The progress of the reaction was observed by thin-layer chromatography. All the reactions were performed in Milestones StartSYNTH microwave. The NMR spectra were recorded on Bruker Avance III 300, 400, and 500 MHz FT NMR Spectrometers. Using azo compound and polymer-bound triphenyl phosphine as a coupling reagent, esterification of different carboxylic acids with alcohols was performed under microwave irradiation.

RESULTS

Esterification of benzoic acid with 1-propanol under microwave irradiation gave a high yield of 92% propyl benzoate in 60 minutes only. Isolation of the ester products was relatively simple as both the byproducts polymer-bound triphenylphosphine oxide and hydrazine could be removed by simple filtration. The rates of reactions were found to be directly proportional to the pKa of the benzoic acids.

CONCLUSION

4,4'-Dinitroazobenzene was introduced as a novel coupling reagent, in conjugation with polymer-bound triphenylphosphine, for esterification reactions under microwave irradiation. The low moisture sensitivity of the reaction system, easy separation of the byproducts, and column chromatographyfree isolation of esters help our methods with application significance, particularly from the 'Sustainable Chemistry' perspective.

Catalyst-free regioselective acetylation of primary hydroxy groups in partially protected and unprotected thioglycosides with acetic acid

Highly regioselective acetylation of primary hydroxy groups in thioglycoside derivatives with gluco- and galacto-configurations was achieved by treatment with aqueous or anhydrous acetic acid (60–100% AcOH) at elevated temperatures (80–118 °C), avoiding complex, costly and time-consuming manipulations with protective groups. Acetylation of both 4,6-O-benzylidene acetals and the corresponding diols as well as the unprotected tetraol with AcOH was shown to lead selectively to formation of 6-O-acetyl derivatives. For example, the treatment of phenyl 1-thio-β-d-glucopyranoside with anhydrous AcOH at 80 °C for 24 h gave the corresponding 6-O-acetylated derivative in 47% yield (71% based on the reacted starting material) and unreacted starting tetraol in 34% yield, which can easily be recovered by silica gel chromatography and reused in further acetylation.

Highly regioselective acetylation of primary hydroxy groups in thioglycoside derivatives was achieved by treatment with aqueous or anhydrous acetic acid (60–100%) at elevated temperatures (80–118 °C), avoiding manipulations with protective groups.

Determination of Optical Purity of Lactic Acid-Based Chiral Liquid Crystals and Corresponding Building Blocks by Chiral High-Performance Liquid Chromatography and Supercritical Fluid Chromatography

Liquid crystals (LCs) are among the most prominent materials of the current information age, mainly due to their well-known application in liquid crystal displays (LCDs). Their unique electro-optical properties stem from their ability to form organised structures (mesophases) on the transition from solid state to isotropic liquid. Molecules of LCs in a mesophase still maintain the anisotropy of solid crystals, while simultaneously exhibiting the fluidity of liquids, which gives the system the ability to react immediately to external stimuli such as electric or magnetic fields, light, mechanical stress, pressure and, of course, temperature. For the proper function of LC-based devices, not only chemical, but also optical purity of materials is strongly desirable, since any impurity could be detrimental to the self-assembly of the molecules. Therefore, in this study we aimed to verify synthetic methods published in the literature, which are used nowadays to prepare chiral building blocks based on lactic acid, for their enantioselectivity. Moreover, we have focused on the development of an analytical chiral separation method for target liquid crystalline materials. Using a chiral polysaccharide-based column operated in liquid chromatography mode, we show that not all published methods of LC synthesis are enantioselective, which could lead to significant differences in the properties of the resulting materials. We show that high-performance liquid chromatography with UV detection and supercritical fluid chromatography with UV and mass spectrometry detection enable full control over the chemical and optical purity of the target LCs and the corresponding chiral building blocks. For the first time, we utilise supercritical fluid chromatography with mass detection for the direct chiral analysis of liquid crystalline materials and impurities formed during the synthesis.

Synthetic Chiral Derivatives of Xanthones: Biological Activities and Enantioselectivity Studies

Many naturally occurring xanthones are chiral and present a wide range of biological and pharmacological activities. Some of them have been exhaustively studied and subsequently, obtained by synthesis. In order to obtain libraries of compounds for structure activity relationship (SAR) studies as well as to improve the biological activity, new bioactive analogues and derivatives inspired in natural prototypes were synthetized. Bioactive natural xanthones compromise a large structural multiplicity of compounds, including a diversity of chiral derivatives. Thus, recently an exponential interest in synthetic chiral derivatives of xanthones (CDXs) has been witnessed. The synthetic methodologies can afford structures that otherwise could not be reached within the natural products for biological activity and SAR studies. Another reason that justifies this trend is that both enantiomers can be obtained by using appropriate synthetic pathways, allowing the possibility to perform enantioselectivity studies. In this work, a literature review of synthetic CDXs is presented. The structures, the approaches used for their synthesis and the biological activities are described, emphasizing the enantioselectivity studies.

Fast, Efficient, and Versatile Synthesis of 6-amino-5-carboxamidouracils as Precursors for 8-Substituted Xanthines

Substituted xanthine derivatives are important bioactive molecules. Herein we report on a new, practical synthesis of 6-amino-5-carboxamidouracils, the main building blocks for the preparation of 8-substituted xanthines, by condensation of 5,6-diaminouracil derivatives and various carboxylic acids using the recently developed non-hazardous coupling reagent COMU (1-[(1-(cyano-2-ethoxy-2-oxoethylideneaminooxy)dimethylaminomorpholinomethylene)]methanaminium hexafluorophosphate). Optimized reaction conditions led to the precipitation of pure products after only 5 to 10 min of reaction time. The method tolerates a variety of substituted 5,6-diaminouracil and carboxylic acid derivatives as starting compounds resulting in most cases in more than 80% isolated yield. Regioselectivity of the reaction yielding only the 5-carboxamido-, but not the 6-carboxamidouracil derivatives, was unambiguously confirmed by single X-ray crystallography and multidimensional NMR experiments. The described method represents a convenient, fast access to direct precursors of 8-substituted xanthines under mild conditions without the necessity of hazardous coupling or chlorinating reagents.

Diphenyl Carbonate: A Highly Reactive and Green Carbonyl Source for the Synthesis of Cyclic Carbonates

A practical, safe, and highly efficient carbonylation system involving a diphenyl carbonate, an organocatalyst, and various diols is presented herein and produces highly valuable cyclic carbonates. In reactions with a wide range of diols, diphenyl carbonate was activated by bicyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst, which successfully replaced highly toxic and unstable phosgene or its derivatives while maintaining the desired high reactivity. Moreover, this new system can be used to synthesize sterically demanding cyclic carbonates such as tetrasubstituted pinacol carbonates, which are not accessible via other conventional methods.

Lactobionic/Folate Dual-Targeted Amphiphilic Maltodextrin-Based Micelles for Targeted Codelivery of Sulfasalazine and Resveratrol to Hepatocellular Carcinoma

In this study, promising approaches of dual-targeted micelles and drug-polymer conjugation were combined to enable injection of poorly soluble anticancer drugs together with site-specific drug release. Ursodeoxycholic acid (UDCA) as a hepatoprotective agent was grafted to maltodextrin (MD) via carbodiimide coupling to develop amphiphilic maltodextrin-ursodeoxycholic acid (MDCA)-based micelles. Sulfasalazine (SSZ), as a novel anticancer agent, was conjugated via a tumor-cleavable ester bond to MD backbone to obtain tumor-specific release, whereas resveratrol (RSV) was physically entrapped within the hydrophobic micellar core. For maximal tumor-targeting, both folic acid (FA) and lactobionic acid (LA) were coupled to the surface of micelles to obtain dual-targeted micelles. The decrease of critical micelle concentration (CMC) from 0.012 to 0.006 mg/mL declares the significance of a dual hydrophobicized core of micelles by both UDCA and SSZ. The dual-targeted micelles showed a great hemocompatibility, as well as enhanced cytotoxicity and internalization into HepG-2 liver cancer cells via binding to overexpressed folate and asialoglycoprotein receptors. In vivo, the micelles demonstrated superior antitumor effects revealed as reduction in the liver/body weight ratio, inhibition of angiogenesis, and enhanced apoptosis. Overall, combined strategies of dual active targeted micelles with bioresponsive drug conjugation could be utilized as a promising approach for tumor-targeted drug delivery.

T1- and T2-weighted Magnetic Resonance Dual Contrast by Single Core Truncated Cubic Iron Oxide Nanoparticles with Abrupt Cellular Internalization and Immune Evasion

Conventional T₁- or T₂-weighted single mode contrast-enhanced magnetic resonance imaging (MRI) may produce false results. Thereby, there is a need to develop dual contrast agents, T₁- and T₂-weighted, for more accurate MRI imaging. The dual contrast agents should possess high magnetic resonance (MR) relaxivities, targeted tumor linking, and minimum recognition by the immune system. We have developed nitrodopamine-PEG grafted single core truncated cubic iron oxide nanoparticles (ND-PEG-tNCIOs) capable of producing marked dual contrasts in MRI with enhanced longitudinal and transverse relaxivities of 32 ± 1.29 and 791 ± 38.39 mM^–1 s^–1, respectively. Furthermore, the ND-PEG-tNCIOs show excellent colloidal stability in physiological buffers and higher cellular internalization in cancerous cells than in phagocytic cells, indicating the immune evasive capability of the nanoparticles. These findings indicate that tNCIOs are strong candidates for dual contrast MRI imaging, which is vital for noninvasive real-time detection of nascent cancer cells in vivo and for monitoring stem cells transplants.

Synthesis, Crystal Structure, and Biological Activity of Ethyl 4-Methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate Polymorphic Forms

Continuing the search for new potential analgesics among the derivatives of 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylic acid, the possibility of obtaining its esters by the alkylation of the corresponding sodium salt with iodoethane in dimethyl sulfoxide (DMSO) at room temperature was studied. It was found that under such conditions, together with the oxygen atom of the carboxyl group, a heteroatom of nitrogen is also alkylated. Therefore, the product of the reaction studied is a mixture of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate (major) and its 1-ethyl-substituted analog (minor). A simple but very effective method of preparative separation of these compounds was proposed. Moreover, the heterogeneous crystallization from ethanol was revealed to result in a monoclinic polymorphic form of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate, while the homogeneous crystallization results in its orthorhombic form. The molecular and crystal structures of both forms were confirmed by X-ray diffraction analysis, and the phase purity by powder diffraction study. The pharmacological tests carried out on the model of a carrageenan edema showed that the screening dose of 20 mg/kg of 1-ethyl-substituted ester and the orthorhombic form of its analog unsubstituted in position 1 exhibited weak anti-inflammatory and moderate analgesic effects. At the same time, the monoclinic form of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate appeared to be both a powerful analgesic and an anti-inflammatory agent that exceeded Piroxicam and Meloxicam in the same doses by these indicators. A detailed comparative analysis of the molecular and crystal structures of two polymorphic forms of ethyl 4-methyl-2,2-dioxo-1H-2λ⁶,1-benzothiazine-3-carboxylate was carried out using quantum chemical calculations of the energies of pairwise interactions between molecules. An explanation of the essential differences of their biological properties based on this was offered.

Synthesis and Explosion Hazards of 4-Azido-l-phenylalanine

A reliable, scalable, cost-effective, and chromatography-free synthesis of 4-azido-l-phenylalanine beginning from l-phenylalanine is described. Investigations into the safety of the synthesis reveal that the Ullman-like Cu(I)-catalyzed azidation step does not represent a significant risk. The isolated 4-azido-l-phenylalanine product, however, exhibits previously undocumented explosive characteristics.

Oxidative C(sp3)–H amidation of tertiary arylamines with nitriles

The first amidation of tertiary arylamines with nitriles via a cascade dehydrogenation/heterocoupling/addition reaction has been developed.

Direct synthesis of acrylate monomers in heterogeneous continuous flow processes

An efficient, safe and convenient laboratory scale continuous flow process for synthesis of (meth)acrylate monomers is described.

Efficient synthesis of esters through oxone-catalyzed dehydrogenation of carboxylic acids and alcohols

An environmentally friendly oxone (20 mol%) catalyzed esterification of carboxylic acids with alcohols has been developed, providing an attractive alternative to the construction of valuable carbonyl esters.

Development of triazine-based esterifying reagents containing pyridines as a nucleophilic catalyst

A novel esterifying reagent containing a nucleophilic catalyst, DMT-3,5-LUT, enables the synthesis of esters from carboxylic acids and alcohols.