Search

The free radical scavenging properties and possible antioxidant activity of 1,3-diphenylpropane-1,3-dione (1) are reported. Pulse radiolysis technique was employed to study the one-electron oxidation of 1 with various radicals viz. CCl3O2•, N3• and•OH in homogeneous aqueous solution. All these radicals reacted with 1 under ambient conditions at almost diffusion controlled rates producing transient species with an absorption maximum around 420 nm that decayed at first order rates. The transient absorption peak was shifted in the case of CCl3OO• radical reaction with 1 due to change in the polarity of the medium. Formation of a stable product with a broad absorption band starting from 400 nm and cut off at 230 nm was observed in the oxidation of 1 with•OH and•N3 radicals. In a biological system also, 1 showed significant inhibitory activity against Fe2+-mediatedlipidperoxidation. Based on these observations, a suitable mechanism for the oxidation of 1 has been proposed.

Plumbagin, a naphthoquinone occurring in the plants belonging to Plumbago sp. is known to have insect growth disrupting activities. In the present study, a comparative evaluation of bioactivities of related naphthoquinones, juglone and menadione and benzoquinones, 2,6-dimethylbenzoquinone and 2,3,6-trimethylbenzoquinone along with 2,6-dimethylhydroquinone have been undertaken using Dysdercus koenigii. The LD50 values of the compounds showed wide variation. Although all the test compounds disrupted the normal growth at sublethal doses, 2,6-dimethylbenzo- quinone and menadione showed activity at low doses.

A convenient mild protocol for oxidation of highly hindered electron rich benzhydrols using DDQ / PbO2 has been developed.

A convenient one-step synthesis of 2,2-dimethylchromans and chromenes using Amberlyst 15 as a catalyst is described.

On irradiation, 2-methyl-2-ethenyl naphtha-4-chromanone 1 undergoes an unusual intramolecular arene–alkene photocyclisation, followed by rearrangements to give a [5.3.1.06,1]benzotricycloundecene, 5.

Condensation between 1-trimethylsilyloxy-3-butanone and trimethylsilyl [2-14C]acetate gave (±) [2-14C]mevalonolactone in one step.

A new method for cyclodehydration of o-hydroxyaryl-β-ketols to 4-chromanones using HMPT is described. The method has general applicability. It is particularly useful for the cyclisation of labile intermediates as exemplified by the synthesis of cannabinoid synthon, 2-methyl-2-(4-methyl-3-pentenyl)-7-methoxy-4-chromanone.

Mevalonic acid lactone (MVA) labelled with stable as we11 as radioactive isotopes continuesto be one of the most widely used substrates in the biosynthesis of terpenoids. Elucidation of several intricate biochemical processes has been possible through the use of carefully chosen specifically 1abelled MVA.1 Attempts to develop new routes to its synthesis have, therefore, been continued and several elegant syntheses have been reported in recent years.2 Wedescribe here a short and efficient synthesis of MVA in which condensation between butan-1-01-3-one (2a) and acetic acid is brought about through their trimethylsilyl (TMS) derivative.3 Usual acidic work up of the reaction brings about cleavage of TMS groups thus obviating deprotection step used in most of the other syntheses.