Determination of lipophilicity of γ‐butyrolactone derivatives with anticonvulsant and analgesic activity using micellar electrokinetic chromatography

The lipophilicity of a library of 30 derivatives of dihydrofuran‐2(3H)‐one (γ‐butyrolactone) was determined by MEKC. Calibration curve prepared for ten reference drugs enabled to calculate partition coefficient (log P) for novel compounds. The results of MEKC analysis were compared with lipophilicity coefficients determined by RP‐TLC (R_M0) and computational (Mlog P, Clog P) methods. Good correlation was observed between the results obtained by both experimental methods: the MEKC parameters log k and relative lipophilicity R_MO. The relationship between determined log P values and results of the computational prediction was weaker. Analysis of the relationship between lipophilicity and anticonvulsant activity showed statistically significant differences between mean values of log P coefficients for group of active (2.18) and inactive (1.51) compounds in the maximal electroshock test.     

Drug–Membrane Interaction on Immobilized Liposome Chromatography Compared to Immobilized Artificial Membrane (IAM), Liposome/Water,and Octan‐1‐ol/Water Systems

The objective of this study was to investigate drug–membrane interaction by immobilized liposome chromatography (ILC; expressed as lipophilicity index log K_s) and the comparison with lipophilicity indices obtained by liposome/H₂O, octan‐1‐ol/H₂O, and immobilized artificial membrane (IAM) systems. A set of structurally diverse monofunctional compounds and drugs (nonsteroidal anti‐inflammatory drugs and β‐blockers) were selected in this study. This set of solutes consists of basic or acidic functionalities which are positively or negatively charged at physiological pH 7.4. No correlation was found between log K_s from ILC and lipophilicity indices from any of the other membrane model systems for the whole set of compounds. For structurally related compounds, significant correlations could be established between log K_s from ILC and lipophilicity indices from IAM chromatography and octan‐1‐ol/H₂O. However, ILC and liposome/H₂O systems only yield parallel partitioning information for structurally related large molecules. For hydrophilic compounds, the balance between electrostatic and hydrophobic interactions dominating drug partitioning is different in these two systems.     

Estimating the lipophilicity of a number of 2‐amino‐1‐cyclohexanol derivatives exhibiting anticonvulsant activity

The lipophilicity of a number of N‐acyl derivatives of trans‐ or cis‐: racemic, (1R,2R)‐ or (1S,2S)‐aminocyclohexanol (1–13) exhibiting anticonvulsant activity was investigated. Their lipophilicity (R_{m 0}) was determined using reversed‐phase thin‐layer chromatography (RP‐TLC) with mixtures of methanol and water as mobile phases. The partition coefficients of compounds 1–13 (log P) were also calculated using two computer programs (Pallas and Chem DU) and compared with R_{m 0}. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigating the Influence of (Deoxy)fluorination on the Lipophilicity of Non‐UV‐Active Fluorinated Alkanols and Carbohydrates by a New log P Determination Method

Property tuning by fluorination is very effective for a number of purposes, and currently increasingly investigated for aliphatic compounds. An important application is lipophilicity (log P) modulation. However, the determination of log P is cumbersome for non‐UV‐active compounds. A new variation of the shake‐flask log P determination method is presented, enabling the measurement of log P for fluorinated compounds with or without UV activity regardless of whether they are hydrophilic or lipophilic. No calibration curves or measurements of compound masses/aliquot volumes are required. With this method, the influence of fluorination on the lipophilicity of fluorinated aliphatic alcohols was determined, and the log P values of fluorinated carbohydrates were measured. Interesting trends and changes, for example, for the dependence on relative stereochemistry, are reported.     

O‐2′,3′‐Ketal‐Nucleolipids of the Cytostatic 5‐Fluorouridine: Synthesis,Lipophilicity, and Acidic Stability

The synthesis of a series of cyclic and acyclic O‐2′,3′‐ketal derivatives of the cancerostatic 5‐fluorouridine ( 2a ) is described. The novel compounds were characterized by ¹H‐ and ¹³C‐NMR, and UV spectroscopy, as well as by elemental analyses. The lipophilicity values (log P, retention times in RP‐18 HPLC) of the cyclic ketals were determined and related to the ring tensions as well as the acid stability of the spiro‐linked ketal rings.     

Synthesis and Inhibitory Activity Evaluation of 2,6‐Disubstituted Purine Derivatives

A series of novel 2,6‐disubstituted purine derivatives were designed and synthesized from 2,6‐dichloropurine. The structures of target compounds were determined by ¹H‐NMR, ¹³C‐NMR, and HRMS. The synthesized compounds were evaluated for their inhibitory activities against lung cancer cell lines of A549 and liver cancer cell lines of Bel‐7402. 2‐(4‐Benzyloxy‐phenylamino)‐6‐(cyclohexylamino)purine( 3 ), 2‐(4‐chloro‐phenylamino)‐6‐(n‐butylamino)purine ( 5 ), 2‐(4‐morpholinoamino)‐6‐(4‐hydroxy‐phenylamino)purine ( 9 ), and 2‐(4‐O‐galactosyl‐phenylamino)‐6‐(cyclohexylamino)purine ( 12 ) exhibited moderate inhibitory activity.     

(E)‐8‐(3‐Chloro­styr­yl)‐1,3,7‐trimethylxanthine,a caffeine derivative acting both as antagonist of adenosine A2A receptors and as inhibitor of MAO‐B

In the crystal structure of (E)‐8‐(3‐chloro­styr­yl)‐1,3,7‐trimethylxanthine (CSC) [systematic name: (E)‐8‐(3‐chloro­styr­yl)‐1,3,7‐trimethyl‐3,7‐dihydro‐1H‐purine‐2,6‐dione], C₁₆H₁₅ClN₄O₂, the xanthine ring and the lateral styryl chain are coplanar. The crystal packing involves mainly parallel stacking of these planar mol­ecules. The electrostatic potential calculated on the crystal structure conformation confirms the pharmacophore elements associated with MAO‐B inhibition.     

2‐Triazolylpyrimido[1,2,3‐cd]purine‐8,10‐diones via 1,3‐dipolar cycloadditions to 2‐ethynylpyrimido[1,2,3‐cd]purine‐8,10‐dione

This paper presents the synthesis of a series of 5,6‐dihydro‐4H,8H‐pyrimido[1,2,3‐cd]purine‐8,10(9H)‐dione ring system derivatives with a [1,2,3]triazole ring bonded in position 2. The procedure is based on cycloaddition of substituted alkyl azides to the terminal triple bond of 5,6‐dihydro‐2‐ethynyl‐9‐methyl‐4H,8H‐pyrimido[1,2,3‐cd]purine‐8,10(9H)‐dione ( 4 ). This cycloaddition produced two regioisomers ?5,6‐dihydro‐9‐methyl‐2‐(1‐substituted‐1H‐[1,2,3]triazol‐5‐yl)‐4H,8H‐pyrimido[1,2,3‐cd]purine‐8,10(9H)‐dione ( 7 ) and 2‐(1‐substituted‐1H‐[1,2,3]triazol‐4‐yl) derivative 8 . The required 2‐ethynyl deriva tive 4 was obtained from the starting 2‐unsubstituted compound 1 by bromination to yield the 2‐bromo derivative 2 , which was converted by Sonogashira reaction to trimethylsilylethyne 3 and finally, the protective trimethylsilyl group was removed by hydrolysis.     

A diaryl‐terminated hexa‐1,5‐diyne‐3,4‐dione

The structure of bis­(4‐tert‐butyl‐2,6‐dimethyl­phenyl)hexa‐1,5‐diyne‐3,4‐dione, C₃₀H₃₄O₂, has been determined, revealing an extended s‐trans conformation of the dione and the two ynone moieties, which are shielded by the flanking methyl substituents. The structural parameters and the packing arrangement suggest little electronic delocalization between the two ynone moieties.     

Synthesis and Antimicrobial Activity of Some New N‐substituted‐5‐arylidene‐thiazolidine‐2,4‐diones

A total of 17 new N‐substituted derivatives ( 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j , 2k and 3b , 3c , 3d , 3e , 3f , 3g , 3h ) of 5‐((2‐phenylthiazol‐4‐yl)methylene) thiazolidine‐2,4‐dione ( 2a ) and 5‐(2,6‐dichloro‐ benzylidene)thiazolidine‐2,4‐dione ( 3a ) were synthesized. The structural elucidation of the newly synthesized compounds was based on elemental analysis and spectroscopic data (MS, ¹H NMR, ¹³C NMR), and their antimicrobial activities were assessed in vitro against several strains of Gram‐positive and Gram‐negative bacteria and one fungal strain (Candida albicans) as growth inhibition diameter. Some of them showed modest to good antibacterial activity against Gram‐negative Escherichia coli and Salmonella typhimurium and Gram‐positive Staphylococcus aureus, Bacillus cereus, and Enterococcus fecalis bacterial strains, whereas almost all the compounds were inactive against Listeria monocytogenes. All of the synthesized compounds showed moderate to very good activity against C. albicans.     

Crystal structure of pharmaceutical cocrystals of 2,6‐diaminopyridine with piracetam and theophylline

Pharmaceutical cocrystals are crystalline solids formed by an active pharmaceutical ingredient and a cocrystal former. The cocrystals 2,6‐diaminopyridine (DAP)–piracetam [PIR; systematic name: 2‐(2‐oxopyrrolidin‐1‐yl)acetamide] (1/1), C₅H₇N₃·C₆H₁₀N₂O₂, (I), and 2,6‐diaminopyridine–theophylline (TEO; systematic name: 1,3‐dimethyl‐7H‐purine‐2,6‐dione) (1/1), C₅H₇N₃·C₇H₈N₄O₂, (II), were prepared by the solvent‐assisted grinding method and were characterized by IR spectroscopy and powder X‐ray diffraction. Cocrystal (I) crystallized in the orthorhombic space group Pbca and showed a 1:1 stoichiometry. The DAP and PIR molecules are linked by an N—H…O hydrogen‐bond interaction. Self‐assembly of PIR molecules forms a sheet of C (4) and C (7) chains. Cocrystal (II) crystallized in the monoclinic P 2₁/c space group and also showed a 1:1 stoichiometry. The DAP and TEO molecules are connected by N—H…N and N—H…O hydrogen bonds, forming an R ₂²(9) heterosynthon. A bidimensional supramolecular array is formed by interlinked DAP–TEO tetramers, producing a two‐dimensional sheet.     

Structural,spectroscopic and first‐principles studies of new aminocoumarin derivatives

The new aminocoumarin derivatives 3‐[1‐(3‐hydroxyanilino)ethylidene]‐3H‐chromene‐2,4‐dione, ( 1 ), 3‐[1‐(4‐hydroxyanilino)ethylidene]‐3H‐chromene‐2,4‐dione, ( 2 ), and 3‐[1‐(2‐hydroxyanilino)ethylidene]‐3H‐chromene‐2,4‐dione, ( 3 ), all C₁₇H₁₃NO₄, were synthesized by reacting an equimolar amount of 3‐acetyl‐4‐hydroxycoumarin and the corresponding aminophenol in absolute ethanol. Structural and spectroscopic analysis of these phases revealed that derivatives ( 1 ) and ( 2 ) are isomers of previously reported ( 3 ) [Brahmia et al. (2013). Acta Cryst. E 69 , o1296]. The crystal structures of meta derivative ( 1 ) and para derivative ( 2 ) were ab initio determined from powder X‐ray diffraction data using the direct‐space approach. Both ( 1 ) and ( 2 ) adopt the orthorhombic space group P2₁2₁2₁. These isomers show hydrogen bonds and rich π–π stacking, together with π…H interactions, which are built by conjugated systems of coumarin and phenol rings. In the crystalline lattice, the packing of ( 1 ) and ( 3 ) are mainly stabilized through O—H…O hydrogen bonding between neighbouring coumarin molecules, while hydrogen bonds between coumarin and water molecules build the stable crystal structure of derivative ( 2 ). A big similarity in the skeletons of the IR spectra of these isomers was noticed. Derivative ( 2 ) exhibits two weak bands which were not present in the spectra of the other two derivatives, at 2370 and 2948 cm^?1, which can be assigned to the O—H vibrations of the solvent (H₂O) trapped in the structure of ( 2 ). These aminocoumarin derivatives display absorption maxima in the visible region, attributed to π–π delocalization involving the whole electronic system of the compounds with a considerable charge‐transfer character originating from the aminophenyl ring and pointing towards the coumarin system which is characterized by a high electron‐accepting character. Additionally, the isolated molecular ground‐state geometries were optimized at the PBE0/TZP level and the electronic properties, molecular electrostatic potential and Hirshfeld charges were determined.     

Triclinic and monoclinic polymorphs of meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene): the high‐yield synthesis of an unexpected product,concomitant polymorphism and configurational disorder

Pyrazolidine‐3,5‐diones and their derivatives exhibit a wide range of biological activities. Seeking to explore the effect of combining a hydrocarbyl ring substituent, as present in sulfinpyrazone (used to treat gout), with a chlorinated aryl ring, as present in muzolimine (a diuretic), we explored the reaction between 1‐phenylpyrazolidine‐3,5‐dione and 4‐chlorobenzaldehyde under mildly basic conditions in the expectation of producing the simple condensation product 4‐(4‐chlorobenzylidene)‐1‐phenylpyrazolidine‐3,5‐dione. However, the reaction product proved to be meso‐(E,E)‐1,1′‐[1,2‐bis(4‐chlorophenyl)ethane‐1,2‐diyl]bis(phenyldiazene), C₂₆H₂₀Cl₂N₄, and a tentative mechanism is proposed. Crystallization from ethanol produces two concomitant polymorphs, i.e. a triclinic form, (I), in the space group P, and a monoclinic form, (II), in the space group C2/c. In both polymorphs, the molecules lie across centres of inversion, but in (II), the molecules are subject to whole‐molecule disorder equivalent to configurational disorder with occupancies of 0.6021 (19) and 0.3979 (19). There are no hydrogen bonds in the crystal structure of polymorph (I), but the molecules of polymorph (II) are linked by C—H...π(arene) hydrogen bonds into complex chains, which are further linked into sheets by C—H...N interactions.     

Synthesis of betulin derivatives and the determination of their relative lipophilicities using reversed‐phase thin‐layer chromatography

A series of superlipophilic or highly lipophilic semisynthetic betulin derivatives was prepared and their relative lipophilicity was measured by reversed‐phase thin‐layer chromatography (RP‐TLC) at different pH values using 1,4‐dioxane–acetate buffer mixtures as mobile phases. Cholesterol, 17β‐estradiol and pure betulin were used as the reference compounds. Linear relationships were found between R_M values and 1,4‐dioxane concentrations in the mobile phases. LogP values were also calculated with computer programs ACD/LogP (ChemSketch 11.0, Advanced Chemistry Development Inc.) and ClogP (Daylight Chemical Information Systems Inc.). The empirical and theoretical data were compared, and the R_M0 values correlated well with logP. Two of the synthesized betulin derivatives are reported for the first time. Copyright © 2009 John Wiley & Sons, Ltd.     

2,6‐Diamino‐9H‐purine monohydrate and bis(2,6‐diamino‐9H‐purin‐1‐ium) 2‐(2‐carboxylatophenyl)acetate heptahydrate: two simple structures with very complex hydrogen‐bonding schemes

Two structures presenting an uncomplexed 2,6‐diaminopurine (dap) group are reported, namely 2,6‐diamino‐9H‐purine monohydrate, C₅H₆N₆·H₂O, (I), and bis(2,6‐diamino‐9H‐purin‐1‐ium) 2‐(2‐carboxylatophenyl)acetate heptahydrate, 2C₅H₇N₆⁺·C₉H₆O₄²⁻·7H₂O, (II). Both structures are rather featureless from a molecular point of view, but present instead an outstanding hydrogen‐bonding scheme. In compound (I), this is achieved through a rather simple independent unit content (one neutral dap and one water molecule) and takes the form of two‐dimensional layers tightly connected by strong hydrogen bonds, and interlinked by much weaker hydrogen bonds and π–π interactions. In compound (II), the fundamental building blocks are more complex, consisting of two independent 2,6‐diamino‐9H‐purin‐1‐ium (Hdap⁺) cations, one homophthalate [2‐(2‐carboxylatophenyl)acetate] dianion and seven solvent water molecules. The large number of hydrogen‐bond donors and acceptors produces 26 independent interactions, leading to an extended and complicated network of hydrogen bonds in a packing organization characterized by the stacking of interleaved anionic and cationic planar arrays. These structural characteristics are compared with those of similar compounds in the literature.     

Three trifluoro­methyl‐substituted protoporphyrinogen IX oxidase inhibitors

The structures of methyl 5‐[2‐chloro‐4‐(trifluoro­methyl)phenoxy]‐2‐nitro­benzoate, C₁₅H₉ClF₃N₃O₅, (I), methyl 2‐chloro‐5‐[3‐methyl‐2,6‐dioxo‐4‐(trifluoro­methyl)‐1,2,3,6‐tetrahydro­pyrimidin‐1‐yl]benzoate, C₁₄H₁₀ClF₃N₂O₄, (II), and 2‐[4‐chloro‐2‐fluoro‐5‐(prop‐2‐ynyloxy)phenyl]‐4‐(trifluoro­methyl)piperidine‐2,6‐dione, C₁₅H₁₀ClF₄NO₃, (III), are similar in their dihedral angles and in the distances between the farthest two atoms. There are two independent molecules in the structure of (I). The dihedral angles between the two aromatic rings in each molecule in (I), between the benzene and tetrahydro­pyrimidine rings in (II), and between the benzene ring and the five‐atom planar portion of the piperidine‐2,6‐dione ring in (III) are 80.78 (11)/89.75 (11), 89.13 (9) and 87.52 (13)°, respectively. The distances between the farthest two atoms, viz. O⋯F in the two molecules of (I), and Cl⋯F in (II) and (III), are 11.763 (7)/11.953 (6), 10.734 (10) and 10.889 (9) Å, respectively. In all three crystal structures, the molecules are linked to generate sheets of molecules via C—H⋯O interactions.     

Micellar liquid chromatography for lipophilicity determination of new biologically active 1,3‐purinodiones

A series of newly synthesized 1,3‐purinodiones with potential anticonvulsant activity, exhibiting affinity to adenosine A₁ and/or A_2A receptors, were subjected to micellar LC (MLC) with SDS as micelle‐forming agent and n‐propanol as organic modifier. Two C18 silica‐based columns were employed in MLC: a particle one and a monolithic. In parallel, those derivatives were also analyzed in RP‐LC on four silica‐based columns and on an immobilized artificial membrane column. The correlations between the relevant logarithms of the retention factors of analytes obtained in MLC, immobilized artificial membrane and RP‐LC systems on the one hand, and the calculated log P (clog P) and log D values (clog D) on the other, were examined. The level of the correlations of retention data from MLC and RP‐LC systems with clog P and clog D obtained is similar but it could be stressed that MLC allows increasing the speed of analysis and using only one mobile phase. Moreover, there is no need of applying an extrapolation procedure in lipophilicity determination. Therefore, the MLC systems, providing chromatographic data in a fast and efficient manner, were demonstrated as promising alternatives to the classical RP‐LC systems to estimate the lipophilicity of drugs and drug candidates.