Robindra N. Baruah

Eremophilane derivatives and other constituents from Senecio species

Abstract The investigation and reinvestigation respectively of 23 Senecio species afforded 11 further cacalol derivatives, a furoeremophilone, 17 eremophilanes, 4 bisabolene derivatives, a shikimic acid derivative, a bis -prenylated p -hydroxybenzaldehyde, menth-2-en- 1,7-diol and a cumol derivative. The configuration of some eremophilanes have been revised. Structures were elucidated by spectroscopic methods. The results are summarized in a table. The chemotaxonomic aspects agree with those of previous investigations.

Further diterpenes from plants of the compositae, subtribe solidagininae

Abstract Six new ent -labdanes were isolated from the aerial parts of Gutierrezia species and nine from Happlopappus pectinatus . Four neoclerodanes and a friedolabdane were obtained from the aerial parts of Haplopappus paucidentatus . From the Grindelia species, in addition to known derivatives of grindelic acid, an arabinoside was isolated. The absolute configuration of the ent -labdanes was determined by transformation of grindelic acid to methyl-6-oxo-7,8-dihydrogrindelate where the configuration was established by the positive Cotton effect. From Solidago petradoria a new abietane derivative was isolated.

Sesquiterpene derivatives from othonna and related species

Abstract The investigation of several South African representatives of the tribe Senecioneae afforded in addition to known compounds a caryophyllene and a bicyclogermacrene derivative, two furoeremophilanes, three bisabolone derivatives and a guaiane derivative.

Germacranolides from Inula cappa

Abstract Authentic Inula cappa DC afforded a known and four unknown germacranolides related to the ineupatorolides as well as a new 2,3-dihydroxy-9-angeloxygermacra-4-en-6,12-olide. A collection previously described as Inula cappa which yielded only flavones was identified as Blumea balsamifera DC.

Guaianolides from Saussurea affinis

Abstract Cynaropicrin, 11β H -11,13-dihydrodesacylcynaropicrin, aguerins A and B, isoamberboin and the new guaianolides saussureolide and 11β H -11,13-dihydrodesacylcynaropicrin 8-β- d -glucoside were isolated from Saussurea affinis .

New 5-methylcoumarins from Ethulia conyzoides

Abstract The isolation of three new terpenoid 5-methylcoumarins in the form of diastereomeric mixtures from a north Indian collection of Ethulia conyzoides is reported. Stereochemistries were deduced by X-ray analysis of a pure acetate isomer obtained on acetylation of one of the diastereomeric mixtures.

Further sesquiterpene lactones from Calea and Viguiera species

Abstract The aerial parts of Calea clematidea gave three new germacranolides, those of Viguiera procumbens two orizabin derivatives and those of V. linearis dihydrobudlein A. In addition to these lactones, several known ones were isolated.

New alicyclic diterpenes and ent-labdanes from gutierrezia solbrigii

Abstract The investigation of the aerial parts of Gutierrezia solbrigii afforded in addition to known compounds nine new ent-labdane derivatives, an aromatic ester and five alicyclic diterpenes. The structures were elucidated by highfield 1H NMR spectroscopy.

Ineupatoriol, a thiophene analogue of ichthyothereol, from Inula eupatorioides

Abstract Ineupatoriol, a thiophene analogue of ichthyothereol, was isolated from Inula eupatorioides . The absolute stereochemistry is that of ichthyothereol.

Some sesqui- and diterpenes from the tribe eupatorieae

Abstract The aerial parts of Trichogonia salviaefolia afforded a new ent -kaurenic acid derivative and a germacranolide which, most likely, is the precursor of the trichosalviolides. The aerial parts of Liatris spicata gave 1α-hydroxybacchotricuneatin A and a guaianolide, which may be the precursor of spicatin. From Brickellia vernicosa some further dehydronerolidol derivatives were isolated.