5-substituted-2-thiohydantoin analogs as a novel class of antitumor agents

Exploration of newly synthesized azo-thiohydantoins as the potential alkaline phosphatase inhibitors via advanced biochemical characterization and molecular modeling approaches

In the current study, Azo-Thiohydantoins derivatives were synthesized and characterized by using various spectroscopic techniques including FTIR, 1H-NMR, 13C-NMR, elemental and HRMS analysis. The compounds were evaluated for alkaline phosphatase activity and it was observed that among all the synthesized compounds, derivative 7e exhibited substantial inhibitory activity (IC50 = 0.308 ± 0.065 µM), surpassing the standard inhibitor (L-Phenyl alanine, IC50 = 80.2 ± 1.1 µM). Along with this, these derivatives were comprehensively examined regarding the electronic properties and reactivity of the synthesized compounds using Density Functional Theory (DFT) calculations, where the results were found very promising and the synthesized compound were found stable. After that, SwissADME evaluations highlighted compounds for their favorable physicochemical properties, including solubility and drug-likeness. Molecular docking exhibited the strong binding affinities of 7f and 7e derivatives with intestinal alkaline phosphatase (IAP), further supported by Molecular Dynamics (MD) simulations. This comprehensive integration of experimental and computational approaches sheds the light on the potential therapeutic applications of the synthesized compounds. By providing a detailed investigation of these aspects, this research opens the avenues for the development of novel pharmacologically active compounds with diverse applications.

One Pot Synthesis and Biological Activity Studies of New Spirooxindoles

This article reports one-pot synthesis of ten novel spirooxindoles using 5-methyl-2-thiohydantoin, isatin derivatives, and malononitrile in good to high yields (65-90 %). The structures of the synthesized compounds were deduced by 1H-NMR, 13C NMR, FT-IR, and Mass spectral data. The antibacterial activity of the compounds was evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) based on the Kirby-Bauer method. According to the obtained data, the synthesized compounds show more activity against Gram-positive bacteria than Gram-negative bacteria. Also, the antioxidant activity of these compounds was measured using the DPPH radical scavenging test method, which showed good to excellent activity (59.65-94.03 %). Among them, the chlorinated derivatives (4 f-j) exhibited more antioxidant activity (84.85-94.03 %) than the other compounds (4 a-e) (56.65-74.4 %) and even ascorbic acid as a standard antioxidant compound (82.3 %).

Camptothecin structure simplification elaborated new imidazo[2,1-b]quinazoline derivative as a human topoisomerase I inhibitor with efficacy against bone cancer cells and colon adenocarcinoma

Camptothecin is a pentacyclic natural alkaloid that inhibits the hTop1 enzyme involved in DNA transcription and cancer cell growth. Camptothecin structure pitfalls prompted us to design new congeners using a structure simplification strategy to reduce the ring extension number from pentacyclic to tetracyclic while maintaining potential stacking of the new compounds with the DNA base pairs at the Top1-mediated cleavage complex and aqueous solubility, as well as minimizing compound-liver toxicity. The principal axis of this study was the verification of hTop1 inhibiting activity as a possible mechanism of action and the elaboration of new simplified inhibitors with improved pharmacodynamic and pharmacokinetic profiling using three structure panels (A-C) of (isoquinolinoimidazoquinazoline), (imidazoquinazoline), and (imidazoisoquinoline), respectively. DNA relaxation assay identified five compounds as hTop1 inhibitors belonging to the imidazoisoquinolines 3a,b, the imidazoquinazolines 12, and the isoquinolinoimidazoquinazolines 7a,b. In an MTT cytotoxicity assay against different cancer cell lines, compound 12 was the most potent against HOS bone cancer cells (IC50 = 1.47 μM). At the same time, the other inhibitors had no detectable activity against any cancer cell type. Compound (12) demonstrated great penetrating power in the HOS cancer cells' 3D-multicellular tumor spheroid model. Bioinformatics research of the hTop1 gene revealed that the TP53 cell proliferative gene is in the network of hTop1. The finding is confirmed empirically using the gene expression assay that proved the increase in p53 expression. The impact of structure simplification on compound 12 profile, characterized by the absence of acute oral liver toxicity when compared to Doxorubicin as a standard inhibitor, the lethal dose measured on Swiss Albino female mice and reported at LD50 = 250 mg/kg, and therapeutic significance in reducing colon adenocarcinoma tumor volume by 75.36 % after five weeks of treatment with compound 12. The molecular docking solutions of the active CPT-based derivative 12 and the inactive congener 14 into the active site of hTop1 and the activity cliffing of such MMP directed us to recommend the addition of HBD and HBA variables to compound 12 imidazoquinazoline core scaffold to enhance the potency via hydrogen bond formation with the major groove amino acids (Asp533, Lys532) as well as maintaining the hydrogen bond with the minor groove amino acid Arg364.

Design, synthesis, molecular modelling and antitumor evaluation of S-glucosylated rhodanines through topo II inhibition and DNA intercalation

In the present study, 5-arylidene rhodanine derivatives 3a-f, N-glucosylation rhodanine 6, S-glucosylation rhodanine 7, N-glucoside rhodanine 8 and S-glucosylation 5-arylidene rhodanines 13a-c were synthesised and screened for cytotoxicity against a panel of cancer cells with investigating the effective molecular target and mechanistic cell death. The anomers were separated by flash column chromatography and their configurations were assigned by NMR spectroscopy. The stable structures of the compounds under study were modelled on a molecular level, and DFT calculations were carried out at the B3LYP/6-31 + G (d,p) level to examine their electronic and geometric features. A good correlation between the quantum chemical descriptors and experimental observations was found. Interestingly, compound 6 induced potent cytotoxicity against MCF-7, HepG2 and A549 cells, with IC₅₀ values of 11.7, 0.21, and 1.7 µM, compared to Dox 7.67, 8.28, and 6.62 µM, respectively. For the molecular target, compound 6 exhibited topoisomerase II inhibition and DNA intercalation with IC₅₀ values of 6.9 and 19.6 µM, respectively compared to Dox (IC₅₀ = 9.65 and 31.27 µM). Additionally, compound 6 treatmnet significantly activated apoptotic cell death in HepG2 cells by 80.7-fold, it induced total apoptosis by 34.73% (23.07% for early apoptosis, 11.66% for late apoptosis) compared to the untreated control group (0.43%) arresting the cell population at the S-phase by 49.6% compared to control 39.15%. Finally, compound 6 upregulated the apoptosis-related genes, while it inhibted the Bcl-2 expression. Hence, glucosylated rhodanines may serve as a promising drug candidates against cancer with promising topoisomerase II and DNA intercalation.

Design, Synthesis, Computational Investigations, and Antitumor Evaluation of N-Rhodanine Glycosides Derivatives as Potent DNA Intercalation and Topo II Inhibition against Cancer Cells

Nitrogen and sulfur glycosylation was carried out via the reaction of rhodanine (1) with α-acetobromoglucose 3 under basic conditions. Deacetylation of the protected nitrogen nucleoside 4 was performed with CH₃ONa in CH₃OH without cleavage of the rhodanine ring to afford the deprotected nitrogen nucleoside 6. Further, deacetylation of the protected sulfur nucleoside 5 was performed with CH₃ONa in CH₃OH with the cleavage of the rhodanine ring to give the hydrolysis product 7. The protected nitrogen nucleosides 11a-f were produced by condensing the protected nitrogen nucleoside 4 with the aromatic aldehydes 10a-f in C₂H₅OH while using morpholine as a secondary amine catalyst. Deacetylation of the protected nitrogen nucleosides 11a-f was performed with NaOCH₃/CH₃OH without cleavage of the rhodanine ring to afford the deprotected nitrogen nucleosides 12a-f. NMR spectroscopy was used to designate the anomers' configurations. To examine the electrical and geometric properties derived from the stable structure of the examined compounds, molecular modeling and DFT calculations using the B3LYP/6-31+G (d,p) level were carried out. The quantum chemical descriptors and experimental findings showed a strong connection. The IC₅₀ values for most compounds were very encouraging when evaluated against MCF-7, HepG2, and A549 cancer cells. Interestingly, IC₅₀ values for 11a, 12b, and 12f were much lower than those for Doxorubicin (7.67, 8.28, 6.62 μM): (3.7, 8.2, 9.8 μM), (3.1, 13.7, 21.8 μM), and (7.17, 2.2, 4.5 μM), respectively. Against Topo II inhibition and DNA intercalation, when compared to Dox (IC₅₀ = 9.65 and 31.27 μM), compound 12f showed IC₅₀ values of 7.3 and 18.2 μM, respectively. In addition, compound 12f induced a 65.6-fold increase in the rate of apoptotic cell death in HepG2 cells, with the cell cycle being arrested in the G2/M phase as a result. Additionally, it upregulated the apoptosis-mediated genes of P53, Bax, and caspase-3,8,9 by 9.53, 8.9, 4.16, 1.13, and 8.4-fold change, while it downregulated the Bcl-2 expression by 0.13-fold. Therefore, glucosylated Rhodanines may be useful as potential therapeutic candidates against cancer because of their topoisomerase II and DNA intercalation activity.

Copper coordination compounds with (5Z,5Z')-2,2'-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones. Comparison with sulfur analogue

A series of new organic ligands (5Z,5Z')-2,2'-(alkane-α,ω-diyldiselenyl)-bis-5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-ones (L) consisting of two 5-(2-pyridylmethylene)-3,5-dihydro-4H-imidazol-4-one units linked with polymethylene chains of various lengths (n = 2-10, where n is the number of CH₂ units) have been synthesized. The reactions of these ligands with CuCl₂·2H₂O and CuClO₄·6H₂O gave Cu²⁺ or Cu¹⁺ containing mono- and binuclear complexes with Cu₂LCl _x (x = 2-4) or CuL(ClO₄) _y (y = 1, 2) composition. It was shown that the agents reducing Cu²⁺ to Cu¹⁺ in the course of complex formation can be both a ligand and an organic solvent in which the reaction is carried out. This fundamentally distinguishes the selenium-containing ligands L from their previously described sulfur analogs, which by themselves are not capable of reducing Cu²⁺ during complexation under the same conditions. A higher cytotoxicity and reasonable selectivity to cancer cell lines for synthesized complexes of selenium-containing ligands was shown; unlike sulfur analogs, ligands L themselves demonstrate a high cytotoxicity, comparable in some cases to the toxicity of copper-containing complexes.

Catalytic Asymmetric Synthesis of Chiral Thiohydantoins via Domino Cyclization Reaction of β,γ-Unsaturated α-Ketoester and N,N'-Dialkylthiourea

The first catalytic asymmetric route to synthesize chiral thiohydantoins containing a quaternary stereogenic center has been established utilizing a chiral phosphoric acid-catalyzed domino cyclization reaction of N,N'-dialkyl thioureas with β,γ-unsaturated...

Green synthesis of thioxoimidazolidine derivative ligand: Spectroscopic, thermal and biological assignments of new Cu(II), Co(II), and Ni(II) chelates in neutral system

Eco-friendly synthesis of ethyl 3-(4-oxo-3-(1-(pyridin-3-yl)ethylideneamino)-2-thioxoimidazolidin-1-yl)propanoate (4) ligand (L) using microwave irradiation technique was described. The structure of thioxoimidazolidine derivative ligand compound has been established based on different types of analyses such as infrared, 1H-NMR, 13C-NMR, and mass spectra as well as elemental analysis. The copper, cobalt, and nickel(II) complexes with molecular formula [M(L)(H2O)4]Cl2 (where M = Co(II), Ni(II), and Cu(II), L = thioxoimidazolidine derivative ligand), have been prepared and well-characterized using microanalytical, conductivity measurements, magnetic, spectroscopic, and physical analyses. Upon the outcome results of analyses, the stoichiometry of the synthesized complexes is 1:1 (M:L). The molar conductance values concluded that the behavior of metal complexes was electrolytes. The 3-(4-oxo-3-(1-(pyridin-3-yl)ethylideneamino)-2-thioxoimidazolidin-1-yl)propanoate chelate acts as a monovalent bidentate fashion via nitrogen and oxygen atoms of both thioxoimidazolidine and propanoate ester moieties. The geometric structures of the synthesized metal complexes are an octahedral configuration based on spectroscopic and magnetic moment studies. The thermogravimetric assignments deduced that the presence of four coordinated water molecules. The synthesized copper(II), cobalt(II), and nickel(II) complexes were biologically checked against G+ and G- bacteria and two species of fungi (Aspergillus Nigaer, and Penicillium Sp.).

Designed Synthesis of Diversely Substituted Hydantoins and Hydantoin-Based Hybrid Molecules: A Personal Account

Hydantoin and its analogues such as thiohydantoin and iminohydantoin have received substantial attention from both a chemical and a biological point of view. Several compounds of this class have shown useful pharmacological activities such as anticonvulsant, antitumor, antiarrhythmic, and herbicidal properties that have led, in some cases, to clinical applications. Because of these broad-spectrum activities, intensive research efforts have been dedicated in industry and academia to the synthesis and structural modifications of hydantoin and its derivatives. Realizing the importance of hydantoin in organic and medicinal chemistry, we also initiated a research program that successfully designed and developed new routes and methods for the formation of hydantoin, thiohydantoin, and iminohydantoin substituted at various positions, particularly at the N-1 position without following a protection–deprotection strategy. Because combinations of two or more pharmacophoric groups can lead to hybrid molecules that display a mixed mechanism of action on biological targets, we extended our developed strategy to the syntheses of new types of hydantoin-based hybrid molecules by combining hydantoin with a triazole, isoxazoline, or phosphate scaffold as a second pharmacophore to exploit their diverse biological functions.

1 Introduction

2 Chemistry and Properties

2.1 Physical Properties

2.2 Chemical Properties

2.3 Biological Properties

3 General Synthetic Methods

4 Synthesis of Diversely Substituted Hydantoins

5 Synthesis of Diversely Substituted Thiohydantoins

6 Synthesis of Diversely Substituted Iminohydantoins

7 Fused or Bicyclic (Thio)hydantoins

8 Di- or Multivalent (Thio)hydantoins

9 Hydantoin-Based Hybrid Molecules

9.1 Hydantoin–Isooxazoline Hybrids

9.2 Hydantoin–Triazole Hybrids

9.3 Hydantoin–Phosphate Hybrids: Phosphorylated Hydantoins

10 Summary and Outlook

Recent Design and Structure-Activity Relationship Studies on the Modifications of DHFR Inhibitors as Anticancer Agents

BACKGROUND

Dihydrofolate reductase (DHFR) has been known for decades as a molecular target for antibacterial, antifungal and anti-malarial treatments. This enzyme is becoming increasingly important in the design of new anticancer drugs, which is confirmed by numerous studies including modelling, synthesis and in vitro biological research. This review aims to present and discuss some remarkable recent advances in the research of new DHFR inhibitors with potential anticancer activity.

METHODS

The scientific literature of the last decade on the different types of DHFR inhibitors has been searched. The studies on design, synthesis and investigation structure-activity relationships were summarized and divided into several subsections depending on the leading molecule and its structural modification. Various methods of synthesis, potential anticancer activity and possible practical applications as DHFR inhibitors of new chemical compounds were described and discussed.

RESULTS

This review presents the current state of knowledge on the modification of known DHFR inhibitors and the structures and searches for about eighty new molecules, designed as potential anticancer drugs. In addition, DHFR inhibitors acting on thymidylate synthase (TS), carbon anhydrase (CA) and even DNA-binding are presented in this paper.

CONCLUSION

Thorough physicochemical characterization and biological investigations highlight the structure-activity relationship of DHFR inhibitors. This will enable even better design and synthesis of active compounds, which would have the expected mechanism of action and the desired activity.

Synthesis, antiviral, DFT and molecular docking studies of some novel 1,2,4-triazine nucleosides as potential bioactive compounds

A novel series of nucleosides with potential antiviral activity have been synthesized and characterized using IR, MS, 1D NMR and 2D NMR data. The antiviral activity of the synthesized compounds was assessed against the Coxsackie B virus and Hepatitis A virus (HAV-10). The results revealed that compound 6 is equipotent to the standard drug Ribavirin against HAV-10. Also, some computational studies, such as the prediction of pharmacokinetic properties, toxicity, and bioactivity, have been done.

Elucidation of the atroposelectivity in the synthesis of axially chiral thiohydantoin derivatives

Recently, Sarigul and Dogan have synthesized a number of enantiomerically enriched axially chiral atropoisomeric 2-thiohydantoins by the reaction of l-amino acid ester salts and o-aryl isothiocyanates in the presence of triethyl amine (TEA) in dichloromethane. The non-axially chiral derivative 5-methyl-3-phenyl-2-thiohydantoin gave a racemic product whereas the axially chiral 5-methyl-3-o-bromophenyl-2-thiohydantoin was less prone to racemize at C5 of the heterocyclic ring. In this study, we present a computational study (M06-2X/6-311+G(d,p) for C, H, O, N and S; M06-2X/6-311++G(3df,3pd) for Br) in order to propose plausible mechanisms for the racemization and cyclization steps for 2-thiohydantoin derivatives. The study includes rationalization based on steric as well as the electrostatic effects to elucidate the epimerization differences at C5.

Synthesis and Antimicrobial Activity of Thiohydantoins Obtained from L-Amino Acids

Background:

Thiohydantoins are an important class of heterocyclic compounds in drug discovery since they are related to a wide range of biological properties including antimicrobial activity.

Objective:

The objective of this study was to synthesize a series of thiohydantoins derived from Laminoacids and to evaluated their inhibitory effect on the growth of Gram-negative and Grampositive bacteria.

Methods:

All title compounds were synthetized by reaction of L-amino acids with thiourea or ammonium thiocyanate. Their antimicrobial activities were evaluated against bacterial strains by broth microdilution assays. The time-kill kinetics, the antibiofilm activity and the cytotoxicity to mammalian cells were determined for the compound that exhibited the best antimicrobial profile (1b).

Results:

Eleven thiohydantoins were readily obtained in good yields (52-95%). In general, thiohydantoins were more effective against Gram-positive bacteria. Compound 1b (derived from Lalanine) showed the best antibacterial activity against Staphylococcus epidermis ATCC 12228 and S. aureus BEC 9393 with MIC values of 940 and 1921 µM, respectively. The time-kill kinetics demonstrated time-dependent bactericidal effect in both strains for this derivative. Besides, 1b also exhibited antibacterial activity against biofilms of S. epidermidis ATCC 12228, leading to a 40% reduction in their metabolic activity compared to the untreated control. No cytotoxicity of 1b to mammalian cells was observed at MIC values.

Conclusion:

The data reported herein indicate relevant antimicrobial activity of thiohydantoins derived from L-aminoacid, mainly 1b, as potential pharmacophore to guide further chemical modification aiming at the search for new and improved antimicrobial agents.

New N-ribosides and N-mannosides of rhodanine derivatives with anticancer activity on leukemia cell line: Design, synthesis, DFT and molecular modelling studies

N-ribosylation and N-mannosylation compounds have a great role in compounds activity as anticancer. The reaction of 2-thioxo-4-thiazolidinone (rhodanine) derivatives, as aglycon part, was done with ribofuranose and mannopyranose sugars (glycone part) followed by deacetylation without cleavage of the rhodanine under acidic medium. Conformational analysis has been studied using NMR methods (2D, DQF-COSY, HMQC and HMBC). All final the new deprotected nucleosides were screened against leukemia 1210, and were found to be considerably less potent (Ic50% 1.4-10.6 μM) than doxorubicin (Ic50% 0.02 μM). Compounds 10d and 10e which contain ribose moiety have better activity than those with mannose sugar. DFT calculations with B3LYP/6-31 + G (d) level were used to analyze the electronic and geometric characteristics deduced from the stable structure of the compounds. The principal quantum chemical descriptors showed a good correlation with the experimental observations. Rapid Overlay Comparison Similarity (ROCS) study was operated to explain the compounds similarity and to figure out the most important pharmacophoric features.

Synthesis, molecular modeling and anti-cancer evaluation of a series of quinazoline derivatives

Quinazolines were surveyed as biologically relevant moieties against different cancer cell lines, so in the present study, we analyzed novel derivatives as target-oriented chemotherapeutic anti-cancer drugs. A series of 3-substituted 2-thioxo-2,3-dihydro-1H-quinazolin-4-ones 4a-e were synthesized via the reaction of 2-aminobenzoic acid (1) with isothiocyanate derivatives 2a-e. S-alkylation and S-glycosylation were carried via the reaction of 4a-e with alkyl halides and α-glycopyranosyl bromides 7a,b under anhydrous alkaline and glycoside conditions, respectively. The S-alkylated and S-glycosylated structures, and not that of the N-alkylated and N-glycosylated isomers, have been selected for the products. Conformational analysis has been studied by homo- and heteronuclear two-dimensional NMR methods (DQF-COSY, HMQC, and HMBC). The S site of alkylation and glycosylation were determined from the ¹H, ¹³C heteronuclear multiple-quantum coherence (HMQC) experiments. All derivatives were subjected to molecular docking calculations, which selected some derivatives (5n, 8c, 8g, 9c, and 9a) as promising ones based on their excellent binding affinities towards the EGFR tyrosine kinase molecular target. The in vitro cytotoxic activity against MCF-7 and HepG2 cell lines showed effective anti-proliferative activity of the analyzed derivatives with lower IC₅₀ values especially 9a with IC₅₀ = 2.09 and 2.08 μM against MCF-7 and HepG2, respectively, and their treatments were safe against the normal cell line Gingival mesenchymal stem cells (GMSC). Moreover, RT-PCR reaction investigated the apoptotic pathway for the compound 9a, which activated the P53 genes and its related genes. So, further work is recommended for developing it as a chemotherapeutic drug.

Highly enantioselective addition of sulfur-containing heterocycles to isatin-derived ketimines

In this study, we report a highly stereoselective addition of sulfur-containing heterocyclic compounds to isatin-derived ketimines efficiently catalyzed by cinchonidine-derived bifunctional tertiary aminothiourea (1 mol%).

Progress on the Chemical Constituents Derived from Glucosinolates in Maca (Lepidium meyenii)

Maca (Lepidium meyenii Walp.), a famous food supplement, has drawn an unprecedented international interest over the last two decades. It was assumed that glucosinolates, macamides, macaenes, and alkaloids are the main bioactive components of Maca before. Recently, a series of novel thiohydantoins which generally exhibit a variety of activities have been isolated from Maca. This review focuses on the progress on the main bioactive components of Maca and their biosynthetic pathway, which indicates that macamides, thiohydantoins, and some alkaloids may originate from glucosinolates. Interestingly, thiohydantoins from Maca are the first type of thiohydantoin derivatives to be found from a natural source and may contribute to some significant effects of Maca.

Design, Synthesis, and Biological Activity of β-Carboline Analogues Containing Hydantoin, Thiohydantoin, and Urea Moieties

A series of novel β-carboline derivatives was designed by combining the anti-tobacco mosaic virus (TMV) lead compound tetrahydro-β-carboline ester with the hydantoin, thiohydantoin, and urea motifs. These derivatives were synthesized from tetrahydro-β-carboline ester via a structural diversity-oriented synthesis in one step, and their biological activities were evaluated. Most of the derivatives exhibited anti-TMV activity higher than that of commercial plant virucide ribavirin, such as compounds 2, 4, 5, 7, 9, 15, 16, 19, and 21. Compared with the lead compounds, some of these derivatives showed good insecticidal activity against Plutella xylostella and Culex pipiens pallens. At the same time, these derivatives also showed broad-spectrum fungicidal activity. The systematic study provides strong evidence that the hydantoin, thiohydantoin, and urea motifs of these molecules can improve and modulate the activities of the analogues of natural products.

1-Benzyl-3-aryl-2-thiohydantoin Derivatives as New Anti-Trypanosoma brucei Agents: SAR and in Vivo Efficacy

A high throughput screening and subsequent hit validation identified compound 1 as an inhibitor of Trypanosoma brucei parasite growth. Extensive structure–activity relationship optimization based on antiparasitic activity led to the highly potent compounds, 1-(4-fluorobenzyl)-3-(4-dimethylamino-3-chlorophenyl)-2-thiohydantoin (68) and 1-(2-chloro-4-fluorobenzyl)-3-(4-dimethylamino-3-methoxyphenyl)-2-thiohydantoin (76), with a T. brucei EC₅₀ of 3 and 2 nM, respectively. This represents >100-fold improvement in potency compared to compound 1. In vivo efficacy experiments of 68 and 76 in an acute mouse model of Human African Trypanosomiasis showed a 100% cure rate after 4 days of oral treatment at 50 mg/kg twice per day.

Positron annihilation lifetime studies of changes in free volume on some biorelevant nitrogen heterocyclic compounds and their S-glycosylation

A series of N-heterocyclic compounds was investigated by positron annihilation lifetime spectroscopy as well as Doppler broadening of annihilation radiation (DBAR) at room temperature. The results showed that the formation probability and life time of ortho-positronium in this series are structure and electron-donation character dependent, and can give more information about the structure. The DBAR provides direct information about the change of core and valance electrons as well as the number of defect types present in these compounds.

Determination of Acid Dissociation Constants (pK a ) of Bicyclic Thiohydantoin-Pyrrolidine Compounds in 20% Ethanol-Water Hydroorganic Solvent

The acid dissociation constants of potential bioactive fused ring thiohydantoin-pyrrolidine compounds were determined by potentiometric titration in 20% (v/v) ethanol-water mixed at 25 ± 0.1°C, at an ionic background of 0.1 mol/L of NaCl using the HYPERQUAD computer program. Proton affinities of potential donor atoms of the ligands were calculated by AM1 and PM3 semiempiric methods. We found, potentiometrically, three different acid dissociation constants for 1a–f. We suggest that these acid dissociation constants are related to the carboxyl, enol, and amino groups.

A new approach for the N- and S-galactosylation of 5-arylidene-2-thioxo-4-thiazolidinones

N- and S-galactosylation was carried out via the reaction of 5-((Z)-arylidene)-2-thioxo-4-thiazolidinones with 2,3,4,6-tetra-O-acetyl-α-d-galactopyranosyl bromide under alkaline conditions or under silylation conditions. Deacetylation of the N-galactosylation products was performed with concentrated hydrochloric acid in methanol (3.5%) or sodium methoxide in methanol without cleavage of the 2-thioxo-4-thaizolidinone ring by means of acid hydrolysis. The anomers were separated by flash column chromatography, and their configurations were assigned by NMR spectroscopy. The deprotected nucleosides were screened against leukemia L-1210 and were found inactive.

A practical approach to new (5Z) 2-alkylthio-5-arylmethylene-1-methyl-1,5-dihydro-4H-imidazol-4-one derivatives

A practical protocol for the preparation of (5Z)-2-alkylthio-5-arylmethylene-1-methyl-1,5-dihydro-4H-imidazol-4-one derivatives is reported. The new compounds were obtained in good yield and stereoselectivity in two steps, namely a solvent-free Knoevenagel condensation under microwave irradiation, followed by an S-alkylation reaction with various halogenoalkanes.