Synthesis and biological screening of 7-hydroxy-4-methyl-2H-chromen-2-one, 7-hydroxy-4,5-dimethyl-2H-chromen-2-one and their some derivatives

7-Hydroxy-4-methyl-2H-chromen-2-one (2), 7-hydroxy-4,5-dimethyl-2H-chromen-2-one (15) and their some derivatives were synthesized for exploring selected biological screening. The compounds 9 and 13 had shown high degree of cytotoxic activity. Three compound 9, 10 and 13 showed high degree of bactericidal activity amongst the present series.     

The role of Rho GTPases in the regulation of the rearrangement of actin cytoskeleton and cell movement

The rearrangement of the actin cytoskeleton has been shown to play a critical role in the development of transformation and malignant phenotype of cancer cells. Rho family GTPases regulate the arrangement of the actin cytoskeleton. By wound-healing assay, we have found that NIH 3T3 fibroblast cells move towards the wound- gaps by extending filopodial and lamellipdial structures at the leading edge of the moving cells. We have inactivated the function of Rho GTPases of v-Ras transformed NIH 3T3 cells by overexpressing Rho GTPase-activating (RhoGAP) domain of RhoGAP of p190. We have observed that inactivation of Rho, Rac and Cdc42 GTPases by overexpressing RHG causes inhibition of: (i) polymerization of actin to form filaments, (ii) formation of lamellipodia, filopodia and stress fibres, (iii) cell motility, (iv) cell spreading and (v) cell-to-cell adhesions. These results further strengthen the current knowledge on the role of Rho, Rac and Cdc42 GTPases in the regulation of the rearrangement of actin cytoskeleton. Our results, for the first time, demonstrate that RhoGAP domain of RhoGAP could be used to study the molecular mechanism of Ras-mediated signalling in growth, differentiation and carcinogenesis.     

Triterpenoids from Psidium guajava leaves

Three pentacyclic triterpenoids including one new guajavanoic acid (2) and two known obtusinin (1) and goreishic acid I (3) have been isolated from the leaves of Psidium guajava. The new constituent 2 has been characterized as 2alpha-hydroxy-3beta-p-E-coumaroyloxyurs-12, 18-dien-28-oic acid through 1H-NMR and 13C-NMR (broad band and DEPT). This is the first report of isolation of compound 1 and 3 from the genus Psidium.     

Reactions of benzothiazolide triosmium clusters with tetramethylthiourea

The valence saturated benzothiazolide triosmium cluster [Os₃(CO)₁₀(μ-η²-C₇H₄NS)(μ-H)] (1) reacts with tetramethylthiourea in refluxing toluene to give [Os₃(CO)₈(μ-η²-C₇H₄NS)(η²-SCNMe₂NMeCH₂)(μ-H)₂] (5), which exists as a mixture of two isomers in solution, whereas the electron-deficient cluster [Os₃(CO)₉(μ₃-η²-C₇H₄NS)(μ-H)] (2) reacts with tetramethylthiourea in refluxing cyclohexane to give two new compounds [Os₃(CO)₈(μ-η²-C₇H₄NS)(η²-SCNMe₂NMeCH₂)(μ-H)₂] (6) and [Os₃(CO)₉(μ-η²-C₇H₄NS)(η¹-SC(NMe₂)₂)(μ-H)] (7). In contrast, the reaction of [Os₃(CO)₉(μ₃-η²-C₇H₃(2-CH₃)NS)(μ-H)](3) with tetramethylthiourea in refluxing cyclohexane at 81 °C, gives only [Os₃(CO)₉(μ-η²-C₇H₃(2-CH₃)NS)(η¹-SC(NMe₂)₂)(μ-H)] (8) in 15% yield. Compound 7 converts into 6 in refluxing toluene whereas a similar thermolysis of 8 results non-specific decomposition. All the compounds have been characterized by elemental analysis, IR, ¹H NMR and mass spectroscopic data together with single crystal X-ray diffraction analysis for 5 and 7. Both compounds 5 and 6 contain a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and are structurally very similar. In 5, the benzothiazolide ligand is coordinated to Os₃ triangle via the nitrogen lone pair and C(2) carbon atom of the heterocyclic ring whereas in 6 the ligand is coordinated to the Os₃ triangle via the nitrogen lone pair and the C(7) carbon atom of carbocyclic ring. In 7 and 8, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom which is also bound to the nitrogen atom of the benzothiazolide ligand.     

Ursethoxy acid,a new triterpene from Lantana camara

A new pentacyclic triterpene, named ursethoxy acid (1) was isolated from the aerial parts of Lantana camara Linn. Its structure has been elucidated as 3,25-epoxy-3alpha-ethoxy-urs-12-en-28-oic acid through extensive 1D- and 2D-NMR (COSY-45, NOESY, J-resolved, HMQC and HMBC) studies.     

Triterpenoidal Secondary Metabolites from Lantana Camara Linn.

Three new pentacyclic triterpenoids, camarin ( 1 ), lantacin ( 2 ), and camarinin ( 3 ) were isolated from the aerial parts of Lantana camara Linn ., together with seven known compounds. The structures of the new constituents were elucidated by chemical transformation, HR‐EI mass spectrometry, and NMR spectroscopy, including 1D (¹H‐ and ¹³C‐NMR) and 2D (¹H,¹H‐COSY, NOESY, ¹H,¹H‐TOCSY, J‐resolved, HMQC, and HMBC) experiments.     

Structural studies of oxalohydroxamic acid by single crystal X-ray diffraction and spectroscopic methods

The structure of oxalohydroxamic acid has been investigated by X-ray and spectroscopic analyses. It has been shown that oxalohydroxamic acid exists in the oxamic form in the solid as well as in solution. The variable-temperature nuclear magnetic resonance (NMR) studies reveal an exchange of OH and NH protons, the exchange being faster at higher temperatures. The kinetic and the thermodynamic parameters such as the rate constant (K), the free energy of activation (G ^DG), and the energy of activation (E _a) for the exchange process have been obtained. The compound crystallizes in the monoclinic space groupP2₁/c witha=5.208,b=3.864,c=11.482 Å,=111.45°, andZ=2. The structure was solved withMultan 80. The refinement by block diagonal least squares and Fourier methods providedR=0.035. There is strong hydrogen bonding between the molecules which form dimer.     

A new natural product and insecticidal amides from seeds of Piper nigrum Linn

Studies on the petroleum ether soluble and insoluble fraction of ethanol extract of dried ground seeds of Piper nigrum resulted in the isolation and structure elucidation of 1 new and 11 known compounds which include 3 hitherto unreported constituents, namely, cinnamylideneacetone, 3,4-methylenedioxyphenylpropiophenone and 2-hydroxy-4,5-methylenedioxypropiophenone from this plant.     

Morphology-controlled assembly of ZnO nanostructures: a bioinspired method and visible luminescence

In a bioinspired methodology, positively charged polypeptides and polyamines directly catalyse ZnO mineralization under "green" conditions of room temperature and neutral pH. The polyamines not only act as mineralizing agents for the formation of ZnO nanoparticles, but also self-assemble the nanoparticles to form spindle-like morphologies at these very ambient conditions. Both the directional growth of ZnO and its luminescent property have a pH dependency. At higher pH, the ZnO shape changes to a rodlike morphology that exhibits green photoluminescence with different intensity than that for ZnO spindles.     

A comparative study of the reactivity of unsaturated triosmium clusters [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] and [Os3(CO)9{μ3-η-C7H3(2-Me)NS}(μ-H)] with BuNC

Treatment of unsaturated [Os₃(CO)₈{μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (2) with ^tBuNC at room temperature gives [Os₃(CO)₈(CNBu^t)){μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os₃(CO)₇(CNBu^t){μ₃-Ph₂PCHP(Ph)C₆H₄}(μ-H)₂] (4). Reaction of the labile complex [Os₃(CO)₉(μ-dppm)(NCMe)] (5) with ^tBuNC at room temperature affords the substitution product [Os₃(CO)₉(μ-dppm)(CNBu^t)] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os₃(CO)₉{μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (7) with ^tBuNC yields the addition product [Os₃(CO)₉(CNBu^t){μ-η²-C₇H₃(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os₃(CO)₈(CNBu^t){μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh₃ at room temperature to give the adduct [Os₃(CO)₈(PPh₃)(CNBu^t){μ-η²-C₇H₃(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies.