Gp Kalena

Amberlyst 15 Catalyzed Prenylation of Phenols: One-Step Synthesis of Benzopyrans

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

A new synthesis of organic trisulfides

Abstract Thiols react with diimidazolylsulfide under mild conditions to give symmetrical trisulfides in good yield and high purity.

Stereo- and regioselectivity of intramolecular 1,2-arene-alkene photocycloaddition in 2-alkenyl-4-chromanones

Abstract Intramolecular 1,2-arene-alkene photocycloaddition of 2-alkenyl-4-chromanones gave complex multicyclic oxatetracyclotetradecanediones which on internal photo- and microwave induced thermal rearrangements provided a diverse array of compounds with [3.3.0]bicyclooctane carbon frame work. The stereo- and regiochemical aspects as well as desymmetrization of alkenyl chromanones due to intramolecular 1,2-arenealkene photocycloaddition have also been discussed.

A novel intramolecular 1,2-arene-alkene photocycloaddition

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.

Insect growth regulatory activity of naturally occurring quinones and their derivatives in Dysdercus koenigii Fabr. (Hem., Pyrrhocoridae)

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‐dimethylbenzoquinone and menadione showed activity at low doses.

DDQ/PbO2: a Novel Oxidation System for Hindered Electron Rich Benzhydrols

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

Synthesis of 2-Hydroxy-4, 6-Dimethoxycrotonophenone A New Class of Natural Products from Dysophylla Stellata Benth

Abstract 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.

A novel intramolecular arene–alkene photocycloaddition in 2-alkenyl naphtha-4-chromanones—a short route to functionalised multicyclic systems

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.

A New Method of Cyclodehydration of 3, 3-Dialkyl-1-Oxo-1-(2-hydroxyaryl) propan-3-ols to 2, 2-Dialkyl-4-chromanones: Synthesis of Cannabinoid Synthon

Abstract 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.

A Short Synthesis of (+)-Mevalonolactone

Abstract 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.