Process Research and Development of a Dihydropyrimidine Dehydrogenase Inactivator: Large-Scale Preparation of Eniluracil Using a Sonogashira Coupling

Novel Pharmaceutical Cocrystals of Tegafur: Synthesis, Performance, and Theoretical Studies

PURPOSE

Tegafur (TF) is one of the most important clinical antitumor drugs with poor water solubility, severely reducing its bioavailability. This work develops new cocrystals to improve the solubility of TF and systematically investigates the intermolecular interactions to provide new insights into the formation of cocrystal and changes in physicochemical properties.

METHOD

In this paper, two new 1:1 cocrystals of TF with 2,4 dihydroxybenzoic acid (2,4HBA) and p-nitrophenol (PNP) were synthesized. The cocrystal products were identified and characterized by various solid state analysis techniques. And the high performance liquid chromatography (HPLC) was conducted to determine the solubility and dissolution rate of TF and cocrystals. Moreover, the quantum chemistry calculations of crystal structure provided theoretical support for the results.

RESULT

Compared with pure TF, the solubility and dissolution rate of TF-2,4HBA is significantly increased in a pH 6.8 buffer at 37°C. Under accelerated storage conditions (40°C, 75% RH), all cocrystal exhibits excellent stability over 8 weeks. Hirshfeld surface (HS) analysis, atoms in molecules (AIM) analysis, interaction region indicator (IRI) analysis, molecular electrostatic potential surface (MEPS) analysis and frontier molecular orbital (HOMO-LUMO) analysis were integrated to understand the hydrogen bonding interaction more comprehensively. The simulation results are in good agreement with the experimental data. The results show that the analysis of physical and chemical properties of TF-PNP cocrystal and TF crystal by quantum chemistry method is reliable at molecular level.

CONCLUSION

These results are helpful to provide guiding methods in the cocrystal development and theoretical study of tegafur.

Mo(vi) complexes of amide-imine conjugates for tuning the selectivity of fluorescence recognition of Y(iii) vs. Pb(ii)

Two amide-imine conjugates, viz. 3-methyl-benzoic acid (4-diethylamino-2-hydroxy-benzylidene)-hydrazide (L1) and 3-methyl-benzoic acid (2-hydroxy-naphthalen-1-ylmethylene)-hydrazide (L2), have been prepared and used for a further synthesis of Mo(vi) complexes (M1 and M2, respectively). Single crystal X-ray diffraction analysis confirmed their structures. Interestingly, M1 selectively recognizes Y3+ and Pb2+ at two different wavelengths, whereas M2 selectively interacts with Y3+ with a significantly high binding constant, 1.3 × 105 M-1. The proposed sensing mechanism involves the displacement of Mo(vi) by Y3+/Pb2+ from respective Mo(vi) complexes. The TCSPC experiment also substantiates the "turn-on" fluorescence process. A logic gate has been constructed utilizing the fluorescence recognition of cations by M1. DFT studies corroborated the cation-probe interactions and allowed exploring the orbital energy parameters.

Assessing the environmental benefit of palladium-based single-atom heterogeneous catalysts for Sonogashira coupling

The Pd-Cu catalysed Sonogashira coupling of terminal alkynes and aryl halides is a cornerstone synthetic strategy for C-C bond formation. Homogeneous organometallic systems conventionally applied are typically not reusable and require efficient downstream Pd removal steps for product purification, making it challenging to fully recover the precious metal. A holistic cradle-to-gate life cycle assessment (LCA) unveils that process footprint can be improved up to two orders of magnitude from repeated catalyst reuse. New classes of heterogeneous catalysts based on isolated metal atoms (single-atom catalysts, SACs) demonstrate promising potential to synergise the benefits of solid and molecular catalysts for efficient Pd utilisation. Here we show that using Pd atoms anchored on nitrogen-doped carbon permits full recovery of the metal and reuse of the catalyst over multiple cycles. A hybrid process using the Pd-SAC with a homogeneous CuI cocatalyst is more effective than a fully heterogeneous analogue based on a bimetallic Pd-Cu SAC, which deactivates severely due to copper leaching. In some scenarios, the LCA-based metrics demonstrate the footprint of the hybrid homogeneous-heterogeneous catalytic process is leaner than the purely homogeneous counterpart already upon single reuse. Combining LCA with experimental evaluation will be a useful guide to the implementation of solid, reusable catalysts for sustainable organic transformations.

A Waste-Minimized Approach to Cassar-Heck Reaction Based on POLITAG-Pd0 Heterogeneous Catalyst and Recoverable Acetonitrile Azeotrope

Three different Pd0 -based heterogeneous catalysts were developed and tested in the Cassar-Heck reaction (i. e., copper-free Sonogashira reaction) aiming at the definition of a waste minimized protocol. The cross-linked polymeric supports used in this investigation were designed to be adequate for different reaction media and were decorated with different pincer-type ionic ligands having the role of stabilizing the formation and dimension of palladium nanoparticles. Among the ionic tags tested, bis-imidazolium showed the best performances in terms of efficiency and durability of the metal catalytic system. Eventually, aqueous acetonitrile azeotrope was selected as the reaction medium as it allowed the best catalytic efficiency combined with easy recovery and reuse. Finally, the synergy between the selected catalyst and reaction medium allowed to obtain highly satisfactory isolated yields of a variety of substrates while using a low amount of metal catalyst. The high performance of the designed POLymeric Ionic TAG (POLITAG)-Pd0 , along with its good selectivity achieved in a copper-free process, also led to a simplified purification procedure allowing the minimization of the waste generated as also proven by the very low E-factor values (1.4-5) associated.

Palladium Catalyst Recycling for Heck-Cassar-Sonogashira Cross-Coupling Reactions in Green Solvent/Base Blend

The identification of a green, versatile, user-friendly, and efficient methodology is necessary to facilitate the use of Heck-Cassar-Sonogashira (HCS) cross-coupling reaction in drug discovery and industrial production in the pharmaceutical segment. The Heck-Cassar and Sonogashira protocols, using N-hydroxyethylpyrrolidone (HEP)/water/N,N,N',N'-tetramethyl guanidine (TMG) as green solvent/base mixture and sulfonated phosphine ligands, allowed to recycle the catalyst, always guaranteeing high yields and fast conversion under mild conditions, with aryl iodides, bromides, and triflates. No catalyst leakage or metal contamination of the final product were observed during the HCS recycling. To our knowledge, a turnover number (TON) up to 2375, a turnover frequency (TOF) of 158 h-1 , and a process mass intensity (PMI) around 7 that decreased around 3 after solvent, base, and palladium recovery, represent one of the best results to date using a sustainable protocol. The Heck-Cassar protocol using sSPhos was successfully applied to the telescoped synthesis of Erlotinib (TON: 1380; TOF: 46 h-1 ).

The recent advancement of low-dimensional nanostructured materials for drug delivery and drug sensing application: A brief review

In this review article, we have presented a detailed analysis of the recent advancement of quantum mechanical calculations in the applications of the low-dimensional nanomaterials (LDNs) into biomedical fields like biosensors and drug delivery systems development. Biosensors play an essential role for many communities, e.g. law enforcing agencies to sense illicit drugs, medical communities to remove overdosed medications from the human and animal body etc. Besides, drug delivery systems are theoretically being proposed for many years and experimentally found to deliver the drug to the targeted sites by reducing the harmful side effects significantly. In current COVID-19 pandemic, biosensors can play significant roles, e.g. to remove experimental drugs during the human trials if they show any unwanted adverse effect etc. where the drug delivery systems can be potentially applied to reduce the side effects. But before proceeding to these noble and expensive translational research works, advanced theoretical calculations can provide the possible outcomes with considerable accuracy. Hence in this review article, we have analyzed how theoretical calculations can be used to investigate LDNs as potential biosensor devices or drug delivery systems. We have also made a very brief discussion on the properties of biosensors or drug delivery systems which should be investigated for the biomedical applications and how to calculate them theoretically. Finally, we have made a detailed analysis of a large number of recently published research works where theoretical calculations were used to propose different LDNs for bio-sensing and drug delivery applications.

Designing Homogeneous Copper-Free Sonogashira Reaction through a Prism of Pd-Pd Transmetalation

Simultaneous introduction of two different palladium (pre)catalysts, one tuned to promote oxidative addition to (hetero)aryl bromide and another to activate terminal alkyne substrate, leads to productive Pd–Pd transmetalation, subsequent reductive elimination, and formation of disubstituted alkyne. This conceptually novel rational design of copper-free Sonogashira reaction enabled facile identification of the reaction conditions, suitable for the synthesis of alkyl, aryl, and heteroaryl substituted alkynes at room temperature with as low as 0.125 mol % total Pd loading.

A supramolecular adduct of tegafur and syringic acid: the first tegafur-nutraceutical cocrystal with perfected in vitro and in vivo characteristics as well as synergized anticancer activities

The in vitro and in vivo properties as well as synergistic antitumor activities of the first tegafur-nutraceutical cocrystal are reported.

Halogenating Enzymes for Active Agent Synthesis: First Steps Are Done and Many Have to Follow

Halogens can be very important for active agents as vital parts of their binding mode, on the one hand, but are on the other hand instrumental in the synthesis of most active agents. However, the primary halogenating compound is molecular chlorine which has two major drawbacks, high energy consumption and hazardous handling. Nature bypassed molecular halogens and evolved at least six halogenating enzymes: Three kind of haloperoxidases, flavin-dependent halogenases as well as α-ketoglutarate and S-adenosylmethionine (SAM)-dependent halogenases. This review shows what is known today on these enzymes in terms of biocatalytic usage. The reader may understand this review as a plea for the usage of halogenating enzymes for fine chemical syntheses, but there are many steps to take until halogenating enzymes are reliable, flexible, and sustainable catalysts for halogenation.

Metal-Ion Displacement Approach for Optical Recognition of Thorium: Application of a Molybdenum(VI) Complex for Nanomolar Determination and Enrichment of Th(IV)

An azine-based molybdenum (Mo(VI)) complex (M1) is exploited for selective detection of thorium (Th(IV)) ions through a metal-ion displacement protocol. Th(IV) displaces Mo(VI) from M1 instantly leading to the formation of the Th(IV) complex, having orange-red emission. Consequently, a red shift of the emission wavelength along with 41-fold fluorescence enhancement is observed. This unique method allows detection of Th(IV) as low as 1.5 × 10^-9 M. The displacement of Mo(VI) from M1 by Th(IV) is established by spectroscopic studies and kinetically followed by the stopped-flow technique. The displacement binding constant for Th(IV) is notably strong, 4.59 × 10⁶ M^-1. Extraction of Th(IV) from aqueous solution to the ethyl acetate medium using M1 has been achieved. The silica-immobilized M1 efficiently enriches Th(IV) from its reservoir through solid-phase extraction. Computational studies (density functional theory) support experimental findings.

Prompt treatment with uridine triacetate improves survival and reduces toxicity due to fluorouracil and capecitabine overdose or dihydropyrimidine dehydrogenase deficiency

Uridine triacetate has been shown to be an effective antidote against mortality and toxicity caused by either overdoses or exaggerated susceptibility to the widely used anticancer agents 5-fluorouracil (5-FU) and capecitabine. However, a direct assessment of efficacy based on when emergency treatment was initiated was not clinically feasible. In this study we used mouse models of 5-FU overdose and of dihydropyrimidine dehydrogenase (DPD) deficiency to compare the efficacy of uridine triacetate in reducing toxicity and mortality when treatment was initiated at time points from 4 to 144 h after administration of 5-FU. We found that uridine triacetate was effective both in the 5-FU overdose and DPD deficiency models. Starting treatment within 24 h was most effective at reducing toxicity and mortality in both models, while treatment starting more than 96 to 120 h after 5-FU was far less effective. Uridine triacetate also reduced mortality in the DPD deficiency model when mice were treated with the 5-FU prodrug capecitabine. The results of this study are supportive of clinical observations and practice, indicating that efficacy declined progressively with later and later treatment initiation. Prompt treatment with uridine triacetate, within 24 h, conferred the greatest protection against 5-FU overexposure.

Nanoparticles based on albumin: preparation, characterization and the use for 5-flurouracil delivery

The aim of the study was to formulate and evaluate nanoparticles based on albumin to deliver 5-fluorouracil. The nanoparticles were prepared by coacervation method. The nanoparticles were characterized for particle size, surface charge, size distribution and drug loading capacity. The drug loading capacity varied from 4.22% to 19.8% (w/w). The mean particle size was 141.9 nm and surface charge was -30.3 mV. The drug loaded particles exerted a bi-phasic release pattern with an initial burst effect followed by a sustained release in pH 7.4 phosphate buffer. The drug release was first order diffusion controlled and the mechanism was Fickian. The drug loaded nanoparticles showed superior cytotoxicity when compared to the free drug.

5-Fluorouracil derivatives: a patent review

INTRODUCTION

The fluorinated analog of uracil 5-FU is an antimetabolite, active against a wide range of solid tumors. The main mechanism of action consists in interfering with DNA synthesis and mRNA translation. However, patients treated with 5-FU display several side effects, a result of its nonspecific cytotoxicity for tumor cells. Numerous modifications of the 5-FU structure have been performed in order to overcome these disadvantages.

AREAS COVERED

In this review, the metabolic pathways, pharmacokinetics and clinical pharmacology of 5-FU are briefly introduced. Moreover, several derivatives developed and patented, including oral 5-FU prodrugs and combinations with other active compounds, are presented. Finally, new innovative methods for administration and vehiculization of 5-FU and its derivatives are described.

EXPERT OPINION

The search for less toxic 5-FU derivatives, which diminish or circumvent some of its disadvantages, has allowed the development of selective antitumor prodrugs and novel methods for tissue-specific drug delivery. Although some of these oral prodrugs are being used clinically, either alone or in combination therapy with other anticancer agents, it seems that the potential of personalized medicine, including pharmacogenomics and targeted therapy with novel 5-FU derivatives, will improve the management and clinical responses of patients treated with 5-FU-based therapy.

Chitosan nanoparticles as a new delivery system for the chemotherapy agent tegafur

BACKGROUND

Despite the very efficient antitumor activity of conventional chemotherapy, generally high doses of anticancer molecules must be administered to obtain the required therapeutic action, simultaneously leading to severe side effects. This is frequently a consequence of the development of multidrug resistance by cancer cells and of the poor pharmacokinetic profile of these agents.

OBJECTIVE

In Order to improve the antitumor effect of tegafur and overcome their important drawbacks, we have investigated its incorporation into a drug nanoplatform based on the biodegradable polymer chitosan.

MATERIALS AND METHODS

Two tegafur loading methods were studied: (i) absorption into the polymeric network (entrapment procedure); and (ii) surface deposition (adsorption procedure) in already formed chitosan nanoparticles.

RESULTS

Tegafur entrapment into the polymeric matrix has yielded higher drug loading values and a slower drug release profile, compared to single surface adsorption. The main factores determining the drug loading to chitosan were identified.

DISCUSSION AND CONCLUSION

Such polymeric colloid present very interesting properties for efficient tegafur delivery to cancer.

Efficient Pd-catalyzed coupling of tautomerizable heterocycles with terminal alkynes via C-OH bond activation using PyBrOP

The direct alkynylation of tautomerizable heterocylcles is described via a two-step process involving in situ C-OH activation with bromotripyrrolidinophosphonium hexafluorophosphate (PyBrOP) followed by Sonogashira coupling with a wide range of alkyl or aryl terminal alkynes using a copper-free system employing PdCl(2)(CH(3)CN)(2) and 2-(dicyclohexylphosphino)biphenyl.

Magnetically modulated nanosystems: a unique drug-delivery platform

Magnetic nanoparticles are attractive targets owing to their unique characteristics that are not shared by bulk materials. Magnetic particles, ranging from nanometer-sized to 1 µm in size, are being used in an increasing number of medical applications. The important properties of magnetic particles for medical applications are nontoxicity, biocompatiblilty, injectability and high-level accumulation in the target tissue or organ. Magnetic nanoparticles modified with organic molecules have been widely used for biotechnological and biomedical applications as their properties can be magnetically controlled by applying an external magnetic field. They offer high potential for numerous biomedical applications, such as cell separation, automated DNA extraction, gene targeting, drug delivery, MRI and hyperthermia. When coated with, for example, an antibody, they can be applied in highly sensitive immunoassays or small substance recoveries. Furthermore, a novel application of magnetic nanoparticles and magnetic forces for tissue engineering, termed ‘magnetic force-based tissue engineering’ has been proposed. Particular attention had been paid to the preparation methods that allow the synthesis of particles of nearly uniform size and shape.

Nucleobase-containing transition metal complexes as building blocks for biological markers and supramolecular structures

The incorporation of metal complexes into nucleobases, nucleosides and nucleotides has provided a focus for the development of many novel compounds with a wide range of applications. In this perspective article the different methods to incorporate transition metal complexes into these species will be described. Applications of these compounds as biological markers, catalysts and how the hydrogen bonding properties may be employed in directing supramolecular assembly in both the solid state and solution will be discussed.

Transition metal vinylidene complexes as supramolecular building blocks: nucleobase-mediated self-assembly of crystals with hexagonal symmetry

Reaction of the ruthenium half sandwich compound RuCl(eta(5)-C(5)H(5))(PPh(3))(2) with the uracil (Ur) substituted alkyne HC[triple bond, length as m-dash]CUr in the presence of halide scavengers NH(4)X (X = PF(6), BF(4), OTf) results in the formation of the vinylidene complexes [Ru([double bond, length as m-dash]C[double bond, length as m-dash]CHUr)(eta(5)-C(5)H(5))(PPh(3))(2)][X] which crystallize in the hexagonal space group P6(3)/m. The hexagonal symmetry inherent to the system is due to the formation of a hydrogen bonded array mediated by the two sets of donor-acceptor units on the uracil, resulting in the formation of a cyclic "rosette" containing six ruthenium cations. In solution the (1)H and (31)P{(1)H} NMR spectra of the vinylidene complexes are both concentration and temperature dependent, in accord with the presence of monomer-dimer equilibria in which the rate of rotation of the vinylidene group is fast on the NMR timescale in the monomeric species, but slow in the dimers. The isoelectronic molybdenum-containing vinylidene complex [Mo(eta(7)-C(7)H(7))(dppe)([double bond, length as m-dash]C[double bond, length as m-dash]CHUr)][BF(4)] (dppe = 1,2-bis(diphenylphosphino)ethane) has also been prepared, but forms symmetric dimers in the solid state.

Palladium-catalyzed cross-coupling reactions in total synthesis

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.

Synthesis and biological evaluation of 5-(alkyn-1-yl)-1-(p-toluenesulfonyl)uracil derivatives

Sonogashira coupling of 5-iodouracil (2) and trimethylsilylacetylene gave 5-(trimethylsilylethynyl)uracil (3), which was deprotected to give 5-ethynyluracil (4). Copper(I)-catalyzed cyclization of 4 gave furo[2,3-d]pyrimidin-2(3H)-one (5). Tosylation of 2 and 4 gave the 1-(p-toluenesulfonyl) derivatives 6 and 7, respectively. The tosylated compound 6 and trimethylsilylacetylene did not undergo Sonogashira coupling, and copper(I)-catalyzed cyclization of 7 did not occur. Coupling of 2 with several terminal alkynes gave 5-(alkyn-1-yl)uracil derivatives (9), which underwent tosylation to produce the targeted 5-(alkyn-1-yl)-1-(p-toluenesulfonyl)uracil compounds (11). Copper(I)-catalyzed cyclization of 9 gave the respective furopyrimidines (10) in low yields. Again, cyclization did not occur with the tosyl derivatives (11). Activity against varicella-zoster virus (VZV) was observed with longer-chain analogues of 9 and 11, and compound 7 showed activity against human cytomegalovirus (HCMV) at near cytotoxic levels.Key words: antiviral screening, furo[2,3-d]pyrimidin-2(3H)-one derivatives, Sonogashira coupling, 1-(p-toluenesulfonyl)pyrimidine derivatives.

Preparation of C-5 Substituted Cidofovir Derivatives

1-[(S)-3-Hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC, cidofovir) was modified by substitution on the base moiety in positions C-5 andN4. Key intermediates of these syntheses, diisopropyl esters of (S)-1-[2-(phosphonomethoxy)-3-(triphenylmethoxy)propyl]-5-alkylcytosines (6and7) prepared from 5-alkyl-4-methoxypyrimidin-2(1H)-ones were transformed to the corresponding 5-substituted cytosine orN4-alkylcytosine derivatives by the action of ammonia or primary amines, respectively. These fully protected phosphonate esters gave by treatment with bromotrimethylsilane followed by hydrolysis free phosphonic acids: 1-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]-5-methylcytosine (5-methyl-HPMPC,10), 5-ethyl-1-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (5-ethyl-HPMPC,11) and a series of 5-ethyl-HPMPC analogues17-21bearing various substituents inN4position (cyclopropyl, cyclopentyl, 2-hydroxyethyl, allyl, 2-(dimethylamino)ethyl). 5-Ethynyl-1-[(S)-3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (5-ethynyl-HPMPC,26) was prepared from 5-iodocytosine derivative23using Sonogashira coupling with (trimethylsilyl)acetylene, CuI and [PdCl2(Ph3P)2]. None of the prepared compounds exhibited antiviral activity in vitro.

A nucleic acid base derivative tethered to a ruthenium carbene complex: hydrogen bonded dimers in both the solid state and solution?

A ruthenium carbene bearing a uracil (Ur) substituent has been prepared and has a dimeric structure in the solid state-the dimer being held together by hydrogen bonds between two uracil groups on neighbouring molecules: evidence for the persistence of this interaction in solution has been obtained.

Palladium-catalyzed cross-alkynylation of aryl bromides by sodium tetraalkynylaluminates

Sodium tetraalkynylaluminates (1-4), prepared from NaAlH4 and terminal alkynes, cross-couple with aryl bromides in the presence of Pd(0) and Pd(II) catalysts. The reactions take place in boiling THF or DME. The process is applicable to both homo- and heterocyclic aryl bromides and can be used for conversion of polybromo compounds into polyalkynes. The reactions are high yielding and selective, free of undesired homocoupling and hydrogenolysis processes. The reagents selectively react with the ring-bound bromine atoms but do not affect chloro, cyano, triflate, or ester functions.