N.P. Damodaran

Studies in sesquiterpenes—XXXVII: Sesquiterpenoids from the essential oil of zingiber zerumbet smith

A complete analysis of the essential oil from the rhizomes of Zingiber zerumbet Smith, is given and the isolation of several new humulene-based sesquiterpenoids is described.

Studies in sesquiterpenes—XXXVIII: Structure of humulene epoxide-I and humulene epoxide-II☆☆☆

Abstract Evidence leading to the assignment of absolute stereostructures I and II to (−)-humulene epoxide-I and (−)-humulene epoxide-II respectively is presented. Partial synthesis of (±)-humulene epoxide-I and -II by epoxidation of humulene, adsorbed on SiO2 gel-AgNO3, with one mole of per acid is described.

Organic reactions in a solid matrix—I : Alumina-induced oxirane rearrangements☆☆☆★

Abstract A fairly generation transformation of methyldialkyl-substituted 1,2-epoxides to the corresponding vinylidene, allylic secondary alcohols, on contact with active Al2O3, is described. A systematic study of some of the reaction variables of this transformation has also been carried out. The epoxides thus studied include those derived from the following olefins: 1-methylcyclopentene, 1-methylcyclohexene, 1-methylcycloheptene, α-pinene and Δ3-carene.

Studies in sesquiterpenes-XXXIX: Structure of humulenols

Abstract (+)-Humulenol-II, a minor component of the volatile oil from the rhizomes of Zingiber zerumbet, is shown to possess the absolute stereostructure I and has been directly correlated with (−)-humulene epoxide-II. The preparation of (+)-humulenol-I is also described.

Organic reactions in a solid matrix—III : Silica gel-induced oxirane rearrangements

Abstract 1-Methyl-1,2-epoxycycloheptane, 2α,3α-epoxypinane and 3α,4α-epoxycarane are shown to undergo typical carbonium ion rearrangements in contact with active silica gel. Humulene epoxide-II and caryophyllene oxide did not undergo any transformation under these conditions. All these results are in complete contrast to their behaviour on exposure to alumina.

Organic reactions in a solid matrix—II : Alumina-induced oxirane rearrangements

Abstract Rearrangement of oxiranes, on contact with active Al2O3, earlier studied with methyldialkyl-substituted 1,2-epoxides, has now been extended to 1,2-dialkyl epoxides (cyclohexene oxide, cycloheptene oxide) and β-himachalene monoepoxide (tetrasubstituted). Isomerisation of citronellol epoxide has been investigated to detect any participation of the OH function in oxirane opening. To gauge the importance of topology of the substrate rearrangement of 3β,4β-epoxycarane has been studied and the results compared with those obtained earlier with 3α,4α-epoxycarane.

Photochemical transformations-II: Organic iodides-II: Citronellyl iodide, 2,3-dihydro-6(z)-farnesyl and 2,3-dihydro-6(e)-farnesyl iodides

Experimental parameters governing π-electrons participation during photolysis of citronellyl iodide have been investigated. Photoproducts resulting from irradiation of 2,3-dihydro-6(Z)- and 2,3-dihydro-6(E)-farnesyl iodides have been characterised.

Meroterpenoids—III : Psoralea corylifolia linn.—3. Synthesis of (±)-bakuchiol methyl ether

A synthesis of (±)-bakuchiol methyl ether, involving Claisen rearrangement of geranyl vinyl ether as the key step, is described. Further thermal reorganisation of the intermediate 3-vinyl-citronellal is discussed.

Photochemical transformations — V a: Organic iodides (part 4) : solution photochemistry of 4-phenyl-l-iodobotane and 4-phenyl-l-bromobutane1,2

Evidence is presented to show that product development from photolysis of 4-phenyl-l-iodobutane occurs essentially from an ionic species. This conclusion is in accord with our earlier suggestion that in the photocyclization of citronellyl iodide and related compounds, carbocations are involved.

Products active on arthropod-5: Insect juvenile hormone mimics: sesquiterpene acids having Jh activity from the wood of cedrus deodara loud

Abstract Juvenile hormone activity of the wood of Cedrus deodara is due to Δ10-dehydroepitodomatuic acid (6) and two new related compounds characterised as Δ7-dehydrotodomatuic acid (8) and 7-hydroxytodomatuic acid (13). Besides these, minor amounts of limonene-8-carboxylic acid, geronic acid, and 4-acetylcyclohex-l-ene-l-carboxylic acid were isolated.