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

The title compound, C16H20O3, was prepared by the photolysis of 7-hydroxy-2-methyl-2-(4-methyl-3-pentenyl)-4-chromanone. The H7 and H9 atoms are in an α configuration. The cyclobutane ring is non-planar, the cyclohexenone ring has a half-chair conformation, the pyranone ring has a sofa conformation and the cycloheptanone ring has a boat conformation. The groups of atoms C11, C12, C13, O14 and C12, C13, O14, C4 are both planar.

A novel intramolecular 1,2-arene-alkene photocycloaddition of 2-alkenyl-7-hydroxy-4-chromanone(1) and its alkyl ethers (2 and 3) to (4α, 7α, 9α)4,8,8-trimethyl-14-oxatetracyclo(6.5.14,13.01,9)tetradeca-12-ene-2,11-dione (4) is described.

The title compound, C16H20O3, was prepared by the photolysis of 7-hydroxy-2-methyl-2-(4-methyl-3-pentenyl)-4-chromanone. The H7 and H9 atoms are in an α configuration. The cyclobutane ring is non-planar, the cyclohexenone ring has a half-chair conformation, the pyranone ring has a sofa conformation and the cycloheptanone ring has a boat conformation. The groups of atoms C11, C12, C13, O14 and C12, C13, O14, C4 are both planar.

A novel method for the prenylation of phenols has been developed using 2-methyl-but-3-ene-2-ol as the prenylating agent in the presence of Amberlyst 15. The prenylated catechols and quinols showed better antioxidant activity than the corresponding non-prenylated compounds in the in vitro DPPH and lipid peroxidation assay. The resorcinol derivatives did not show significant antioxidant activity.

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

2-Hydroxy-4, 6-dimethoxycrotonophenone (1), isolated from the plant Dysophylla stellata Benth. by Joshi and Ravindranath,1 is the only example of an open chain form of chromanones. The co-occurrence of the crotonophenone (1) with chromone and butyrophenone1 suggests that these are biogenetically related in the same way as chalcones are to flavonoids.2 It is likely that more crotono-phenones and 2-methylchromanones will be discovered in nature.

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.