Maniruddin Ahmed

Sesquiterpene lactones and other constituents from Schistostephium species

Abstract From four Schistostephium species, in addition to known compounds, 43 new ones were isolated, three isocomene, two bisabolene, two eudesmane, two allo-himachalene and two nerolidol derivatives, two sesquiterpenes with a new carbon skeleton derived from isocomene, nine eudesmanolides, 20 6,12- and 8,12-germacranolides respectively, and a prostaglandin-like acid. The structures were elucidated by spectroscopic methods, especially high field 1 H NMR and some chemical transformations. The stereochemistry of some 8,12-germacranolides was established by partial synthesis which required revision of the previous assignments of the configuration of inunolide, its 4,5- and 1,10-epoxide, vernudifloride, simsiolide, 6-hydroxy-1,10-epoxyinunolide and perhaps also of tanachin. The chemotaxonomic situation is discussed briefly.

Eudesmane derivatives from Verbesina species

Abstract The investigation of seven Verbesina species afforded, in addition to known compounds, several new eudesmane and germacrane derivatives, all bearing a cinnamate or derivatives as residue. Furthermore, a new bisabolene aldehyde and two acetophenone derivatives were isolated. The structures were elucidated mainly by spectroscopic methods and some chemical transformations. The chemotaxonomic situation is discussed briefly.

Germacranolides and diterpenes from Viguiera species

Abstract The investigation of six Viguiera species afforded in addition to known compounds two new diterpenes, the 9,11-dehydro derivatives of trachylobanic and stachenic acid, two new heliangolides closely related to viguiestenin, and the acetate of falcarinol. The chemotaxonomic situation is discussed briefly.

New sesquiterpene lactones, geranyllinalol derivatives and other constituents from Geigeria species

Abstract The investigation of three Geigeria species and five subspecies afforded, in addition to known compounds, the following 32 new compounds: two geigeranolides with a new carbon skeleton, two xanthanolides, five guaianolides, three pseudoguaianolides, a sesquiterpene related to ivaxillarin, a nerolidol derivative, 15 geranyllinalol derivatives, two thiophene acetylenes and a dimeric coniferyl isobutyrate. The structures and the stereochemistry of the new compounds were elucidated by spectroscopic methods and a few chemical transformation. Chemotaxonomic aspect and relationship of the comnounds are discussed.

Diterpenes related to grindelic acid and further constituents from Grindelia species

Abstract The aerial parts of Grindelia stricta afforded in addition to known compounds 21 diterpenes, all closely related to grindelic acid. The aerial part

Dimeric sesquiterpene lactones and kolavane derivatives from Gochnatia paniculata

Abstract Gochnatia paniculata afforded two dimeric sesquiterpene lactones, which are derived from dehydrozaluzanin C, two α-curcumene derivatives and eight kolavane derivatives. The structures were elucidated by spectroscopic methods, especially by highfield 1 H NMR spectroscopy. The chemotaxonomy of this genus is discussed briefly.

Bisabolene derivatives and other constituents from Coreopsis species

Abstract The investigation of five Coreopsis species afforded in addition to typical compounds isolated previously two new perezone derivatives, a coniferyl alcohol derivative and a diacetylenic compound.

Sesquiterpenes from Kleinia species

Abstract The investigation of four Kleinia species afforded, in addition to known compounds, seven new germacrane and three oplopane derivatives, all highly oxygenated. This kind of sesquiterpene seems to be characteristic of the genus Kleinia and related succulent species, and its tentative grouping is discussed.

Labdane and eudesmane derivatives from Ageratum fastigiatum

Abstract Several diterpenes, triterpenes, ent-labdanes, and eudesmane derivatives have been isolated from Ageratum fastigiatum. A previously unknown eud

Caryophyllane derivatives from Pulicaria scabra

Abstract The investigation of Pulicaria scabra afforded in addition to known compounds seven new caryophyllane derivatives, three of them etherified with a caryophyllane derivative and one esterified with a caryophyllane derived alcohol. The structures were elucidated by high field 1 H NMR spectroscopy. The chemistry of this species is similar to that of P. dysenterica but differs from that of the other genera of the subtribe Inulinae.