Isoaurones: synthesis and stereochemical assignments of geometrical isomers

A series of isoaurones have been synthesized for the first time from substituted acetophenones via benzo-2(3H)-furanone in three steps. Geometrical isomers of the isoaurones were separated. The differences in the proton and carbon NMR spectra of the E- and Z-isoaurones afford a useful method for distinguishing between the two isomers. Marginalin, a metabolite of Dytiscus marginalis has been synthesized and the spectral data of the synthetic E-isomer were in good agreement with those of the natural product. The antioxidant activity of isoaurones was determined by superoxide free radical (NBT) method and isoaurones 12 and 13 displayed excellent antioxidant activity.     

Transformations of lignans. Part 11: Oxidation of diphyllin with hypervalent iodine reagents and reductive reactions of a resulting 1-methoxy-1-aryl-4-oxonaphthalene lactone

Treatment of diphyllin 4 with phenyliodonium diacetate (PIDA) in methanol affords a 1-methoxy-1-aryl-4-oxonaphthalene lactone 6. Reduction of 6 with lithium aluminium hydride yields, inter alia, 3,4-dihydrodiphyllin 13, while reaction with sodium in ethanol yields 8 as a major product. These reactions illustrate that selective oxidation followed by reduction provides a facile route for the conversion of a 1-arylnaphthalene lactone to novel functionalised naphthalene and dihydronaphthalene derivatives. Of particular interest is that the oxidation indirectly activates the methylene position (C-10) of the γ-lactone, which may then potentially be substituted to give a new series of lignans. Reaction of 6 with hydroxylamine and benzyloxyamine also proceeds by way of initial attack at C-10.     

Plane Symmetric String Cosmological Models in?Zero-Mass Scalar Fields

Non-static plane symmetric cosmological solutions are studied with zero mass scalar fields in the context of cosmic strings in general relativity. Some physical and geometrical features of these models are discussed.     

Two new macrocyclic diaryl ether heptanoids from Boswellia ovalifoliolata

The stems of Boswellia ovalifoliolata BAL. & HENRY (Burseraceae) afforded two new macrocyclic diaryl ether heptanoids, ovalifoliolatin A (1) and B (2) together with three known compounds; acerogenin C (3), 3 alpha-hydroxyurs-12-ene (4), and sitost-4-en-3-one (5). The structures were established by means of spectroscopic analysis and compounds 1, 3-5 were evaluated for their antibacterial activity.     

Thermal behaviour of (NH4)3VO2F4 and Na(NH4)2VO2F4

The thermal behaviour of (NH₄)₃VO₂F₄ and Na(NH₄)₂VO₂F₄ was investigated using TG, DTA and DSC techniques. The occurrence of a first order phase transition with the onset of decomposition in both the compounds is confirmed. The temperature, energetics and hysteresis of the transition are obtained. A possible path for the thermal degradation is given for both the compounds, and the residues are identified.     

New lignans from the heartwood of cleistanthus collinus

The isolation and characterisation of five new compounds and nine known compounds from the heartwood of Cleistanthus collinus are reported. The new compounds are wodeshiol 16,3,4-dihydrotaiwanin C 20, and three new glycosides 24, 25 and 26 of diphyllin and taiwanin E The ¹H and ¹³C NMR spectra of these compounds are also reported.