MyMedR

Fulltext 2-Cyano-quinolin-1-ium hydrogen sulfate

Loh WS, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 11):o2709.

PMID: 21588923 DOI: 10.1107/S160053681003878X

The title salt, C(10)H(7)N(2) (+)·HSO(4) (-), is formed by the transfer of a proton from H(2)SO(4) to the N atom of 2-cyano-quinoline during crystallization. The quinoline ring system is approximately planar with a maximum deviation of 0.013 (3) Å. In the crystal, the cations are linked to the anions via inter-molecular N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds, forming a layered network.

Fulltext 8-Hy-droxy-quinolin-1-ium nitrate

Loh WS, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 11):o2907-8.

PMID: 21589082 DOI: 10.1107/S1600536810039395

In the title salt, C(9)H(8)NO(+)·NO(3) (-), the quinoline ring system is essentially planar with a maximum deviation of 0.043 (1) Å. In the crystal, an R(2) (2)(7) ring motif is formed by inter-molecular N-H⋯O and C-H⋯O hydrogen bonds between the cation and the anion. In addition, inter-molecular O-H⋯O and C-H⋯O hydrogen bonds link the two ions, generating an R(2) (2)(8) ring motif. These sets of ring motifs are further linked into a ribbon along the a axis via inter-molecular C-H⋯O hydrogen bonds.

Fulltext 2-Cyano-quinolin-1-ium nitrate

Loh WS, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 11):o2726-7.

PMID: 21588937 DOI: 10.1107/S1600536810039243

A proton is transferred from the nitric acid to the N atom of 2-cyano-quinoline during crystallization, resulting in the formation of the title salt, C(10)H(7)N(2) (+)·NO(3) (-). The quinolinium ring system is approximately planar, with a maximum deviation of 0.013 (3) Å. In the crystal, a very asymmetric bifurcated N-H⋯(O,O) hydrogen bond to two O atoms of an adjacent nitrate anion occurs, generating an R(2) (1)(4) ring motif. C-H⋯O hydrogen bonds link the ions into sheets stacking along the a axis.

Fulltext Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives

Hemamalini M, Loh WS, Quah CK, Fun HK

Chem Cent J, 2014;8:31.

PMID: 24887234 DOI: 10.1186/1752-153X-8-31

Co-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.

Fulltext 1-[5-(2H-1,3-Benzodioxol-5-yl)-3-(4-methyl-phen-yl)-2-pyrazolin-1-yl]ethanone

Loh WS, Razak IA, Abdul Rahiman M, Ravikumar GN

Acta Crystallogr Sect E Struct Rep Online, 2013 May 1;69(Pt 5):o726.

PMID: 23723878 DOI: 10.1107/S1600536813008817

In the title compound, C19H18N2O3, the pyrazoline ring is close to being planar (r.m.s. deviation = 0.035 Å) and subtends dihedral angles of 2.11 (8) and 82.63 (8)° with the p-tolyl and benzene rings, respectively. In the crystal, C-H⋯O and C-H⋯N hydrogen bonds link the mol-ecules, forming a three-dimensional network. A weak C-H⋯π inter-action involving the benzene ring is also observed.

Fulltext 2-(4-Meth-oxy-phenyl)-2-oxoethan-aminium chloride

Fun HK, Loh WS, Viveka S, Dinesha, Nagaraja GK

Acta Crystallogr Sect E Struct Rep Online, 2012 Oct 1;68(Pt 10):o2987.

PMID: 23125762 DOI: 10.1107/S1600536812039645

In the cation of the title compound, C(9)H(12)NO(2) (+)·Cl(-), the dihedral angle between the 2-oxoethanaminium N-C-C(=O)- plane [maximum deviation = 0.0148 (12) Å] and the benzene ring is 7.98 (8)°. The meth-oxy group is approximately in-plane with the benzene ring, with a C-O-C-C torsion angle of -2.91 (18)°. In the crystal, the cations and chloride anions are connected by N-H⋯Cl and C-H⋯Cl hydrogen bonds, forming a layer parallel to the bc plane. A C-H⋯π inter-action further links the layers.

Fulltext Quinoline-2-carbonitrile-fumaric acid (1/0.5)

Loh WS, Quah CK, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 9):o2357.

PMID: 21588699 DOI: 10.1107/S1600536810032745

The asymmetric unit of the title compound, C(10)H(6)N(2)·0.5C(4)H(4)O(4), consists of one quinoline-2-carbonitrile mol-ecule and a half-mol-ecule of fumaric acid, which lies on an inversion center. The quinoline-2-carbonitrile mol-ecule is almost planar, with an r.m.s. deviation of 0.008 (1) Å. The acid and base are linked together via pairs of inter-molecular C-H⋯O and O-H⋯N hydrogen bonds, forming R(2) (2)(8) ring motifs. In the crystal, the carbonitrile mol-ecules are further linked by inter-molecular C-H⋯N hydrogen bonds, generating R(2) (2)(10) ring motifs, resulting in zigzag chains running along the c axis.

Fulltext Quinoline-2-carbonitrile

Loh WS, Quah CK, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 9):o2396.

PMID: 21588729 DOI: 10.1107/S1600536810033118

In the title compound, C(10)H(6)N(2), the mol-ecule is almost planar, with an r.m.s. deviation of 0.014 Å. The dihedral angle between the aromatic rings is 1.28 (16)°. In the crystal, mol-ecules are stacked along the a axis by way of weak aromatic π-π stacking inter-actions between the benzene and pyridine rings of adjacent mol-ecules [centroid-centroid separation = 3.7943 (19) Å].

Fulltext 8-Hy-droxy-quinolinium 2-carb-oxy-acetate

Quah CK, Loh WS, Hemamalini M, Fun HK

Acta Crystallogr Sect E Struct Rep Online, 2010;66(Pt 9):o2254.

PMID: 21588617 DOI: 10.1107/S1600536810030990

In the title compound, C(9)H(8)NO(+)·C(3)H(3)O(4) (-), the cation and anion are each essentially planar, with maximum deviations of 0.043 (1) and 0.060 (1) Å, respectively. The dihedral angle between these two planes is 2.20 (4)°. The conformation of the anion is stabilized by an intra-molecular O-H⋯O hydrogen bond, which forms an S(6) ring motif. The hy-droxy group of the oxine unit makes a hydrogen bond with the one of the O atoms of the carboxyl-ate group of the 2-carb-oxy-acetate anion. Two other carboxyl-ate O atoms form R(2) (2)(7) ring motifs via inter-molecular C-H⋯O and N-H⋯O hydrogen bonds. The crystal structure is consolidated by weak inter-molecular C-H⋯O inter-actions, which link the cations and anions into a three-dimensional network.

Fulltext Bis-(3,5-diamino-4H-1,2,4-triazol-1-ium) 3,4-dioxocyclo-butane-1,2-diolate

Fun HK, Loh WS, Johnson A, Yousuf S, Eno E

Acta Crystallogr Sect E Struct Rep Online, 2013 Mar 1;69(Pt 3):o353-4.

PMID: 23476545 DOI: 10.1107/S160053681300322X

The asymmetric unit of the title compound, 2C2H6N5(+)·C4O4(2-), contains two 3,5-diamino-4H-1,2,4-triazolium cations and one squarate dianion. The squaric acid mol-ecule donated one H atom to each of the two 3,5-diamino-1,2,4-triazole mol-ecules at their N atoms. The squaric acid dianion has four C-O bonds which are shorter than a normal single C-O bond (1.426 Å) and are slightly longer than a normal C=O bond (1.23 Å), which indicates the degree of electron delocalization in the dianion. In the crystal, the cations and dianions are linked by N-H⋯N and N-H⋯O hydrogen bonds into a three-dimensional network.

Fulltext (2E)-1-[2,3-Dichloro-6-methyl-5-(trifluoro-meth-yl)phen-yl]-2-(1-phenyl-ethyl-idene)hydrazine

Fun HK, Loh WS, Bhat M, Arulmoli T, Nagaraja GK

Acta Crystallogr Sect E Struct Rep Online, 2012 Nov 1;68(Pt 11):o3189.

PMID: 23284500 DOI: 10.1107/S1600536812042419

The title compound, C(16)H(13)Cl(2)F(3)N(2), exists in an E conformation with respect to the C=N bond [1.2952 (11) Å] and the C-N-N=C torsion angle is 175.65 (8)°. The dihedral angle between the benzene rings is 42.09 (4)°. An intra-molecular C-H⋯F hydrogen bond generates an S(6) ring. In the crystal, the mol-ecules are linked into [101] chains by C-H⋯F hydrogen bonds.

Fulltext Crystal structure of tetra-aqua-bis(3,5-di-amino-4H-1,2,4-triazol-1-ium)cobalt(II) bis-[bis-(pyridine-2,6-di-carboxyl-ato)cobaltate(II)] dihydrate

Johnson A, Mbonu J, Hussain Z, Loh WS, Fun HK

Acta Crystallogr E Crystallogr Commun, 2015 Jun 1;71(Pt 6):m139-40.

PMID: 26090171 DOI: 10.1107/S2056989015010014

The asymmetric unit of the title compound, [Co(C2H6N5)2(H2O)4][Co(C7H3NO4)2]2·2H2O, features 1.5 Co(II) ions (one anionic complex and one half cationic complex) and one water mol-ecule. In the cationic complex, the Co(II) atom is located on an inversion centre and is coordinated by two triazolium cations and four water mol-ecules, adopting an octa-hedral geometry where the N atoms of the two triazolium cations occupy the axial positions and the O atoms of the four water mol-ecules the equatorial positions. The two triazole ligands are parallel offset (with a distance of 1.38 Å between their planes). In the anionic complex, the Co(II) ion is six-coordinated by two N and four O atoms of the two pyridine-2,6-di-carboxyl-ate anions, exhibiting a slightly distorted octa-hedral coordination geometry in which the mean plane of the two pyridine-2,6-di-carboxyl-ate anions are almost perpendicular to each other, making a dihedral angle of 85.87 (2)°. In the crystal, mol-ecules are linked into a three-dimensional network via C-H⋯O, C-H⋯N, O-H⋯O and N-H⋯O hydrogen bonds.

Fulltext Synthesis, structural and antioxidant studies of some novel N-ethyl phthalimide esters

Chidan Kumar CS, Loh WS, Chandraju S, Win YF, Tan WK, Quah CK, et al.

PLoS One, 2015;10(3):e0119440.

PMID: 25742494 DOI: 10.1371/journal.pone.0119440

A series of N-ethyl phthalimide esters 4(a-n) were synthesized and characterized by spectroscopic studies. Further, the molecular structure of majority of compounds were analysed by single crystal X-ray diffraction studies. The X-ray analysis revealed the importance of substituents on the crystal stability and molecular packing. All the synthesized compounds were tested for in vitro antioxidant activity by DPPH radical scavenging, FRAP and CUPRAC methods. Few of them have shown good antioxidant activity.

Fulltext Structural correlation of some heterocyclic chalcone analogues and evaluation of their antioxidant potential

Kumar CS, Loh WS, Ooi CW, Quah CK, Fun HK

Molecules, 2013 Sep 26;18(10):11996-2011.

PMID: 24077177 DOI: 10.3390/molecules181011996

A series of six novel heterocyclic chalcone analogues 4(a-f) has been synthesized by condensing 2-acetyl-5-chlorothiophene with benzaldehyde derivatives in methanol at room temperature using a catalytic amount of sodium hydroxide. The newly synthesized compounds are characterized by IR, mass spectra, elemental analysis and melting point. Subsequently; the structures of these compounds were determined using single crystal X-ray diffraction. All the synthesized compounds were screened for their antioxidant potential by employing various in vitro models such as DPPH free radical scavenging assay, ABTS radical scavenging assay, ferric reducing antioxidant power and cupric ion reducing antioxidant capacity. Results reflect the structural impact on the antioxidant ability of the compounds. The IC₀ values illustrate the mild to good antioxidant activities of the reported compounds. Among them, 4f with a p-methoxy substituent was found to be more potent as antioxidant agent.

Fulltext Heteroaryl chalcones: design, synthesis, X-ray crystal structures and biological evaluation

Kumar CS, Loh WS, Ooi CW, Quah CK, Fun HK

Molecules, 2013 Oct 15;18(10):12707-24.

PMID: 24132195 DOI: 10.3390/molecules181012707

Chalcone derivatives have attracted increasing attention due to their numerous pharmacological activities. Changes in their structures have displayed high degree of diversity that has proven to result in a broad spectrum of biological activities. The present study highlights the synthesis of some halogen substituted chalcones 3(a-i) containing the 5-chlorothiophene moiety, their X-ray crystal structures and the evaluation of possible biological activities such as antibacterial, antifungal and reducing power abilities. The results indicate the tested compounds show a varied range of inhibition values against all the tested microbial strains. Compound 3c with a p-fluoro substituent on the phenyl ring exhibits elevated antimicrobial activity, whereas the compounds 3e and 3f displayed the least antimicrobial activities. The compounds 3d, 3e, 3f and 3i showed good ferric and cupric reducing abilities, and the compounds 3b and 3c showed the weakest reducing power in the series.

Fulltext Synthesis and crystal structures of N-substituted pyrazolines

Loh WS, Quah CK, Chia TS, Fun HK, Sapnakumari M, Narayana B, et al.

Molecules, 2013 Feb 20;18(2):2386-96.

PMID: 23429377 DOI: 10.3390/molecules18022386

Four pyrazole compounds, 3-(4-fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazole-1-carbaldehyde (1), 5-(4-bromophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole-1-carbaldehyde (2), 1-[5-(4-chlorophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl]ethanone (3) and 1-[3-(4-fluorophenyl)-5-phenyl-4,5-dihydro-1H-pyrazol-1-yl]propan-1-one (4), have been prepared by condensing chalcones with hydrazine hydrate in the presence of aliphatic acids, namely formic acid, acetic acid and propionic acid. The structures were characterized by X-ray single crystal structure determination. The dihedral angles formed between the pyrazole and the fluoro-substituted rings are 4.64(7)° in 1, 5.3(4)° in 2 and 4.89(6)° in 3. In 4, the corresponding angles for molecules A and molecules B are 10.53(10)° and 9.78(10)°, respectively.

Fulltext Synthesis and Crystallographic Insight into the Structural Aspects of Some Novel Adamantane-Based Ester Derivatives

Kumar CS, Kwong HC, Mah SH, Chia TS, Loh WS, Quah CK, et al.

Molecules, 2015;20(10):18827-46.

PMID: 26501248 DOI: 10.3390/molecules201018827

Adamantyl-based compounds are commercially important in the treatments for neurological conditions and type-2 diabetes, aside from their anti-viral abilities. Their values in drug design are chronicled as multi-dimensional. In the present study, a series of 2-(adamantan-1-yl)-2-oxoethyl benzoates, 2(a-q), and 2-(adamantan-1-yl)-2-oxoethyl 2-pyridinecarboxylate, 2r, were synthesized by reacting 1-adamantyl bromomethyl ketone with various carboxylic acids using potassium carbonate in dimethylformamide medium at room temperature. Three-dimensional structures studied using X-ray diffraction suggest that the adamantyl moiety can serve as an efficient building block to synthesize 2-oxopropyl benzoate derivatives with synclinal conformation with a looser-packed crystal packing system. Compounds 2a, 2b, 2f, 2g, 2i, 2j, 2m, 2n, 2o, 2q and 2r exhibit strong antioxidant activities in the hydrogen peroxide radical scavenging test. Furthermore, three compounds, 2p, 2q and 2r, show good anti-inflammatory activities in the evaluation of albumin denaturation.

Fulltext The crystal structure of zwitterionic 2-{[(4-imin-iumyl-3-methyl-1,4-di-hydro-pyridin-1-yl)meth-yl]carbamo-yl}benzoate hemihydrate

Chidan Kumar CS, Sim AJ, Ng WZ, Chia TS, Loh WS, Kwong HC, et al.

Acta Crystallogr E Crystallogr Commun, 2017 Jul 01;73(Pt 7):927-931.

PMID: 28775853 DOI: 10.1107/S2056989017007836

The asymmetric unit of the title compound, C15H15N3O3·0.5H2O, comprises two 2-{[(4-iminiumyl-3-methyl-1,4-di-hydro-pyridin-1-yl)meth-yl]carbamo-yl}benzoate zwitterions (A and B) and a water mol-ecule. The dihedral angles between the pyridine and phenyl rings in the zwitterions are 53.69 (10) and 73.56 (11)° in A and B, respectively. In the crystal, mol-ecules are linked by N-H⋯O, O-H⋯O, C-H⋯O and C-H⋯π(ring) hydrogen bonds into a three-dimensional network. The crystal structure also features π-π inter-actions involving the centroids of the pyridine and phenyl rings [centroid-centroid distances = 3.5618 (12) Å in A and 3.8182 (14) Å in B].

Fulltext Design, Synthesis and Docking Studies of Flavokawain B Type Chalcones and Their Cytotoxic Effects on MCF-7 and MDA-MB-231 Cell Lines

Abu Bakar A, Akhtar MN, Mohd Ali N, Yeap SK, Quah CK, Loh WS, et al.

Molecules, 2018 Mar 08;23(3).

PMID: 29518053 DOI: 10.3390/molecules23030616

Flavokawain B (1) is a natural chalcone extracted from the roots of Piper methysticum, and has been proven to be a potential cytotoxic compound. Using the partial structure of flavokawain B (FKB), about 23 analogs have been synthesized. Among them, compounds 8, 13 and 23 were found in new FKB derivatives. All compounds were evaluated for their cytotoxic properties against two breast cancer cell lines, MCF-7 and MDA-MB-231, thus establishing the structure-activity relationship. The FKB derivatives 16 (IC50 = 6.50 ± 0.40 and 4.12 ± 0.20 μg/mL), 15 (IC50 = 5.50 ± 0.35 and 6.50 ± 1.40 μg/mL) and 13 (IC50 = 7.12 ± 0.80 and 4.04 ± 0.30 μg/mL) exhibited potential cytotoxic effects on the MCF-7 and MDA-MB-231 cell lines. However, the methoxy group substituted in position three and four in compound 2 (IC50 = 8.90 ± 0.60 and 6.80 ± 0.35 μg/mL) and 22 (IC50 = 8.80 ± 0.35 and 14.16 ± 1.10 μg/mL) exhibited good cytotoxicity. The lead compound FKB (1) showed potential cytotoxicity (IC50 = 7.70 ± 0.30 and 5.90 ± 0.30 μg/mL) against two proposed breast cancer cell lines. It is evident that the FKB skeleton is unique for anticancer agents, additionally, the presence of halogens (Cl and F) in position 2 and 3 also improved the cytotoxicity in FKB series. These findings could help to improve the future drug discovery process to treat breast cancer. A molecular dynamics study of active compounds revealed stable interactions within the active site of Janus kinase. The structures of all compounds were determined by ¹H-NMR, EI-MS, IR and UV and X-ray crystallographic spectroscopy techniques.

Fulltext Design, synthesis and cytotoxic effects of curcuminoids on HeLa, K562, MCF-7 and MDA-MB-231 cancer cell lines

Zamrus SNH, Akhtar MN, Yeap SK, Quah CK, Loh WS, Alitheen NB, et al.

Chem Cent J, 2018 Mar 19;12(1):31.

PMID: 29556774 DOI: 10.1186/s13065-018-0398-1

BACKGROUND: Curcumin is one of the leading compound extracted from the dry powder of Curcuma longa (Zingiberaceae family), which possess several pharmacological properties. However, in vivo administration exhibited limited applications in cancer therapies.

RESULTS: Twenty-four curcumin derivatives have synthesized, which comprises cyclohexanone 1-10, acetone 11-17 and cyclopentanone 18-24 series. All the curcuminoids were synthesized by the acid or base catalyzed Claisen Schmidt condenstion reactions, in which β-diketone moiety of curcumin was modified with mono-ketone. These curcuminoids 1-24 were screened against HeLa, K562, MCF-7 (an estrogen-dependent) and MDA-MB-231 (an estrogen-independent) cancer cell lines. Among them, acetone series 11-17 were found to be more selective and potential cytotoxic agents. The compound 14 was exhibited (IC50 = 3.02 ± 1.20 and 1.52 ± 0.60 µg/mL) against MCF-7 and MDA-MB-231 breast cancer cell lines. Among the cyclohexanone series, the compound 4 exhibited (IC50 = 11.04 ± 2.80, 6.50 ± 01.80, 8.70 ± 3.10 and 2.30 ± 1.60 µg/mL) potential cytotoxicity against four proposed cancer cell lines, respectively. All the curcucminoids were characterized with the detailed1H NMR, IR, UV-Vis, and mass spectroscopic techniques. The structure of compound 4 was confirmed by using the single X-ray crystallography. Additionally, we are going to report the first time spectral data of (2E,6E)-2,6-bis(2-methoxybenzylidene)cyclohexanone (1). Structure-activity relationships revealed that the mono-carbonyl with 2,5-dimethoxy substituted curcuminoids could be an essential for the future drugs against cancer diseases.

CONCLUSIONS: Curcuminoids with diferuloyl(4-hydroxy-3-methoxycinnamoyl) moiety with mono carbonyl exhibiting potential cytotoxic properties. The compound 14 was exhibited (IC50 = 3.02 ± 1.20 and 1.52 ± 0.60 µg/mL) against MCF-7 and MDA-MB-231 breast cancer cell lines.

Displaying all 20 publications