The structure, stereochemistry, and conformation of theonellapeptolide IIIe (1), a new 36-membered ring cyclic peptolide from the New Zealand deep-water sponge Lamellomorpha strongylata, is described. The sequence of the cytotoxic peptolide was determined through a combination of NMR and MS-MS techniques and confirmed by X-ray crystal structure analysis, which, with chiral HPLC, established the absolute stereochemistry.
Two known, but previously uncharacterized, oii-kaurenic acid derivatives, 1 and 2, and four new sesquiterpenes of the eudesmanolide type, 3-6, have been isolated from Wedelia prostata. The structures were eludidated by a range of ID and 2D high field nmr techniques, and the stereochemistry of the new eudesmanolides was defined from a combination of coupling constant analyses and nuclear Overhauser difference spectra.Plants of the family Compositae have been characterized by the production of structurally varied sesquiterpene lactones that include germacranolides (1), eudesmanolides (2,3), guaianolides (4), pseudoguaianolides (5), and xanthanolides (6). These commonly co-occur with diterpenoid «Jf-kaurenic acid derivatives (2,3), which is of particular relevance to our present report.Wedelia prostata Jacquin is a common herbaceous vine growing in thickets along streams and behind sand dune areas in many parts of the Philippines. It was investigated because of its wide use as a hair colorant and hair tonic, and because it is reported to have beneficial properties in the treatment of such diverse maladies as coughs, cephalagic skin diseases, and uterine hemorrhages (7). We here report the isolation and identification of the free acids of the known (2,8) «tf-kaurenic acid derivatives 1 and 2 and of four new eudesmanolide sesquiterpenes 5-6 from W. prostata.
RESULTS AND DISCUSSIONCHC13 extraction of the ground leaves of W. prostata afforded a 5% organic extract. Rapid chromatography (9) of the crude extract on a Si gel column with increasing proportions of EtOAc in petroleum ether as eluent afforded two «tf-kaurenic free acid derivatives, one of which (1) possessed a tiglate ester function while the other (2) possessed a cinnamate ester function. The methyl esters of these acids were reported by Bohlmann and co-workers (2,8), who isolated them after methylation of the acid-containing fraction of the extract of Wedelia trilobata. The structures 1 and 2 were established on the basis of extensive 2D nmr experimentation. The 3a-ester drawn in
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