Volume 63, Issue 1

The title complex [Co(C 7 H 8 N 5 S) 2 ]·2H 2 O has been synthesized and characterized by IR and UV spectral studies. The structure of the compound has been determined by single-crystal X-ray diffraction. The complex consists of discrete monomeric molecules with octahedrally hexacoordinate cobalt(II) ions, where two acetylpyrazine thiosemicarbazones act as NNS tridentate ligands coordinated to the central cobalt atom via the pyrazine nitrogen, azomethine nitrogen and sulfur atoms. Hydrogen bonds link the different components to stabilize the crystal structure. The antitumor activity of the title complex was tested against A549 lung cancer cell line. The complex exhibited lower antitumor activity, as compared to the free ligand.

The synthesis, crystal structure and magnetic properties of [Mn(III)L(H 2 O)] 2 (H 2 O)(ClO 4 ) (1)(L = N,N'-bis(rac-5-chlorosalicylidenato)-1,2-diaminopropane) are reported. Compound 1 consists of a structurally dinuclear system in which two Mn ions are bridged by the oxygen atoms of μ-phenoxo ligands. Low temperature magnetic susceptibility measurements show a ferromagnetic intra-dimer interaction with J = +1.75 cm −1 , g = 2.01 and α = −0.32.

A six-coordinate manganese (II) complex with the tripod ligand tris(2-benzimidazolylmethyl) amine (ntb), with composition [Mn(ntb) (4-hydroxycinnamate)](4-hydroxycinnamate) · (DMF) 0.5 · (H 2 O) 3 , was synthesized and characterized by elemental and thermal analyses, electrical conductivity, IR, and UV/vis spectral measurements. The crystal structure of the complex has been determined by the single-crystal X-ray diffraction. The Mn (II) cation is bonded to an ntb ligand and a 4-hydroxycinnamate ligand through four N atoms and two O atoms, giving a distorted octahedral coordination geometry. Cyclic voltammograms of the complex indicate a quasi-reversible Mn 3+ /Mn 2+ couple. The X-band EPR spectrum of the complex exhibits a six-line manganese hyperfine splitting pattern with g = 2, A = 95, and confirms that the material is high-spin Mn(II).

Two novel polyoxotungstate-based rare earth compounds, [(C 5 H 5 N-CO 2 ) 2 Ln(H 2 O) 3 ] 2 - [H 2 W 12 O 40 ] · nH 2 O (C 5 H 5 N-CO 2 = pyridine-4-carboxylate; Ln = La 3+ (1), n = 5; Ce 3+ (2), n = 7), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra and TG analyses. The isostructural compounds 1 and 2 exhibit onedimensional (1D) zig-zag chains, in which the dinuclear lanthanide complexes act as bridging linkers and the [H 2 W 12 O 40 ] 6− groups serve as bidentate ligands. The results of cyclic voltammetry (CV) show that compounds 1 and 2 undergo two two-electron redox processes, similar to that of the parent (NH 4 ) 6 [H 2 W 12 O 40 ] ·3H 2 O, and also reveal that the pH of the supporting electrolytic solution has a notable effect on the electrochemical behavior of compound 2.

The N-lithioborazine LiH 2 N 3 B 3 Me 3 , 1, reacts with organoboron halides not only to the respective borazinyl organylboranes but also by Me/halogen exchange. (Me 2 N) 2 B-H 2 N 3 B 3 Me 3 was obtained from 1 and (Me 2 N) 2 BCl. A new ten-membered B 6 N 4 ring system, 5, results on treatment of Cl(Me 2 N)B-B(NMe 2 )Cl with 1. The B-N-borazinyl borazines 6 - 8 can be prepared from 1 and B-monohalo borazines. The synthesis of 2,4,6-trimethylborazinyl-aluminum and -titanium compounds is achieved only with mononuclear monohalides of Al(III) and Ti(IV). The 2,4,6-trimethylborazinyl- bis(piperidino)alane 9 and the tris(2,6-diisopropylphenoxo)-2,4,6-trimethylborazinyltitanium 10 were characterized by X-ray structure analysis. The distortion of the borazine ring by B and N substitution is discussed. In case of the N-substituted borazines YH 2 N 3 B 3 Me 3 the B-N bonds of the YNB 2 units are elongated, e. g. for Y = PBr 2 or (RO) 3 Ti, while N lithiation leads to a shortening of these B-N bond. These changes of bond lengths are also reflected by changes in the B1-N2 and B3-N3 bond lengths which become shorter in the presence of electron-withdrawing groups, but longer in case of Li substitution. Also, the bond angles B1-N2-B2 and B2-N3-B3 are affected by an increase of up to 128°.

The influence of methyl substitution on the thermodynamic parameters for the binding of [Fe(DMP) 3 ] 2+ and [Fe(TMP) 3 ] 2+ (DMP = 4,7-dimethyl-1,10-phenanthroline, TMP = 3,4,7,8-tetramethyl- 1,10-phenanthroline) to calf thymus DNA (ct-DNA) has been studied by determining their equilibrium binding constants (K b ) at various salt concentrations and temperatures. K b of the iron(II) complexes to ct-DNA decreases with the salt concentration in the solution, suggesting considerable electrostatic interaction in the ct-DNA binding of the iron(II) complexes. In contrast, K b of the DNA binding increases with temperature, indicating that the DNA binding reaction of the complex is endothermic and entropically driven. The evaluation of the non-electrostatic binding constant (K 0 t ) based on polyelectrolyte theory has revealed that the K 0 t portions of the total binding constant (K b ) are relatively large and reach 46.4% for [Fe(DMP) 3 ] 2+ at [Na + ] = 0.075 M and 43.9% for [Fe(TMP) 3 ] 2+ at [Na + ] = 0.100 M. The contribution of non-electrostatic binding free energy (ΔG 0 t ) to total binding free energy change (ΔG 0 ) is extremely large, i. e. > 90% for both iron(II) complexes at [Na + ] = 0.05 M, suggesting that the stabilization of the DNA binding is mainly contributed from the non-electrostatic process. The effect of methyl substitution on electrostatic (ΔG 0 pe ) and non-electrostatic (ΔG 0 t ) binding free energy changes has been systematically evaluated using the quantity of ΔΔG 0 pe and ΔΔG 0 t relative to that of the parent iron(II) complex, [Fe(phen) 3 ] 2+ . The results indicate that the substitution of hydrogen atoms in the phen ligand by methyl groups decreases slightly the electrostatic binding free energy changes, but tremendously increases the non-electrostatic ones to yield net binding free energy changes which are more favorable for the ct-DNA binding.

The present work investigates the possibility of using 2'-oxoethyl flavin (2) as a starting material for the construction of more complicated flavin-based molecules. 2'-Oxoethyl flavin (2), prepared by oxidative degradation of commercially available riboflavin 1, is however a rather untypical aldehyde. It prefers the hydrated gem-diol form 4 in aqueous solution. Ab initio electronic structure calculations, carried out at the level of Møller-Plesset perturbation theory of second order (MP2), predict the existence of an intramolecular hydrogen bond between one of the hydroxy groups of the diol and the N1 atom of the flavin skeleton. This result is supported by 1 H NMR measurements which indicate an interaction between the hydroxy groups and the conjugated ring system. We postulate that this rather strong intramolecular hydrogen bond is the origin of the enhanced stability of the gem-diol over the aldehyde form 2. Synthetic applicability of 2'-oxoethyl flavin 2 is limited by low solubility in most organic solvents and sensitivity to basic conditions. The aldehyde functional group is surprisingly reluctant to nucleophilic attack, and several reactions quite typical for aldehydes failed. Nevertheless, reductive amination led to the expected secondary amine 7. Solubility of the molecule thus increased, and a new amino group was introduced.

Antipyrylsemisquaric chloride (9) has been prepared with excellent yield from antipyrylsemisquaric acid (8) and oxalic dichloride in the presence of dimethylformamide. Reaction of 9 with N and S nucleophiles afforded antipyrylsemisquaric acid derivatives, such as amides 12a - t, 14a - e, 15, hydrazides 18a - e, and thioesters 21a - i.

A one-pot synthesis of sterically congested electron-poor N-vinyl pyrazoles in fairly good yields by the reaction of ethyl 3-phenyl-2-propynoate, pyrazoles and triphenylphosphine is reported. The structures of these compounds were confirmed by IR, 1 H, and 13 C NMR spectroscopy, and single crystal X-ray structure determination. The structural analysis of the products indicated that the reaction is completely regio- and stereoselective.

A series of heterocycles was synthesized by the reaction of α,β -unsaturated ketones of benzopyrans or coumarins with various nucleophiles in aqueous medium bearing two points of diversity. Compared to an identical library generated by conventional parallel synthesis, a microwaveassisted procedure dramatically decreased reaction times from hours to minutes, and yields of products and intermediates were improved remarkably. This synthetic approach is ecofriendly in nature which features water as solvent, microwave irradiation, and usage of a “green” catalyst (K 2 CO 3 ).

A green chemistry-based highly regioselective synthesis of ethyl (9-anthryl)glyoxylate was achieved by solvent-free Friedel-Crafts reaction at r. t. Several derivatives of ethyl (9-anthryl)glyoxylate were also synthesized. Ethyl (9-anthryl)hydroxyacetate was obtained almost quantitatively by reduction of ethyl (9-anthryl)glyoxylate with NaBH 4 , and (9-anthryl)methoxyacetic acid was prepared by methylation of ethyl (9-anthryl)hydroxyacetate with CH 3 I in the presence of Ag 2 O and hydrolysis of ethyl (9-anthryl)methoxyacetate. The hydrolysis of ethyl (9-anthryl)hydroxyacetate gave racemic (9-anthryl)hydroxyacetic acid, and the racemate was successfully resolved by crystallization of the diastereomeric salts resulting from the reaction of (±)-(9-anthryl)hydroxyacetic acid with (-)-ephedrine. As a byproduct, crystals containing racemic (±)-(9-anthryl)hydroxyacetate and protonated (-)-ephedrine were isolated and their structures determined by X-ray diffraction.

A new series of coumarin and benzofuran derivatives were synthesized as potential non-nucleoside reverse transcriptase inhibitors (NNRTIs) by reacting, separately, 4-bromomethylcoumarins, their sulphonyl chlorides, and ethyl 3-(bromomethyl)-6-methoxy-1-benzofuran-2-carboxylate with different imidazoles and their benzo analogs. The antiviral (HIV-1, HIV-2) properties of the newly synthesized compounds were investigated in vitro and all compounds were found to be inactive, except 10 which showed inhibition of HIV-2 with EC 50 > 0.51 μgmL−1. The in vitro cytotoxicity of 17 and 19 was assayed against a panel of tumor cell lines consisting of CD4 human T-cells.

From the methanol extract of the fruits of Forsythia koreana two new compounds, one phenylethanoid glycoside and one pyrrolidine alkaloid, have been isolated together with six known compounds. The structures of the isolated compounds were elucidated on the basis of 1D and 2D NMR spectroscopic methods and comparison with literature data.

Three new steroidal saponins were isolated from the roots of Smilax officinalis Kunth. Their structures were established as (3β,5β,22α,25S)-26-(β-D-glucopyranosyloxy)-22-hydroxyfurostan- 3-yl O-α-L-arabinopyranosyl-(1→6)-O-[β-D-glucopyranosyl-(1→4)]-β-D-glucopyranoside, (3β,5α,22α,25S)-26-(β-D-glucopyranosyloxy)-22-hydroxyfurostan-3-yl O-α-L-arabinopyranosyl-( 1→6)-O-[β-D-glucopyranosyl-(1→4)]-β-D-glucopyranoside and (3β,5α,6β,22α,25S)-26-(β- D-glucopyranosyloxy)-6,22-dihydroxyfurostan-3-yl O-α-L-arabinopyranosyl-(1→6)-O-[β-D-glucopyranosyl-( 1→4)]-β-D-glucopyranoside. Their structure elucidations were performed using detailed analyses of 1 H and 13 C NMR spectra including 2D NMR spectroscopic techniques (DEPT, COSY, HSQC, HMBC and HMQC) and chemical conversions.

A new triterpenoid saponin, olean-12-ene-3β ,19β ,24-triol-3-O-β -D-glucopyranoside, named sigmoiside F and a new triterpenoid, 3β -n-propyloxy-β -amyrin, were isolated from the methanolic extract of the stem bark of Erythrina sigmoidea. Their structures were characterized by chemical and spectral analysis.

Chromatographic investigation of the methylene chloride/methanol extract of the aerial parts of Achillea ligustica afforded a new chlorine-containing sesquiterpene lactone as well as two known compounds. The structures of the compounds were determined by comprehensive NMR studies, including DEPT, COSY, NOE, HMQC, HMBC and HRMS. The neurotrophic activity of the new compound has been measured.

Chemical investigation of the EtOH extract of the aerial parts of Scyphiphora hydrophyllacea Gaertn. F. collected from Hainan resulted in the isolation of the two new noriridoids hydrophylin A (1) and hydrophylin B (2). The structures were elucidated by a study of their physical and spectral data.

A new spiroaxane sesquiterpene (15-hydroxy-6α,12-epoxy-7β ,10αH,11β H-spiroax-4-ene, 1) was isolated from the culture broth of the basidiomycete Pholiota adiposa. The structure of 1 was established on the basis of MS, IR, ID, and 2D NMR experiments.

A novel sesquiterpene named cyclopinol (1) together with two related known compounds, cyclocalopin A (2) and Oacetylcyclocalopin A (3), has been isolated from the basidiomycete Boletus calopus. The structure of compound 1 was established on the basis of spectral methods (MS, IR, 1D, and 2D NMR experiments).