title: Lepadins F-H, new cis-decahydroquinoline alkaloids from the Australian ascidian Aplidium tabascum.
abstract: Chemical investigation of a Great Barrier Reef ascidian, Aplidium tabascum, has resulted in the isolation of three new cis-decahydroquinoline alkaloids, lepadins F-H (4-6). The three new compounds differ from the previously isolated lepadins A-C (1-3) in that they contain a fully saturated 5-hydroxyoctyl side chain attached at C-5, an unsaturated eight-carbon ester moiety attached to C-3, and opposite stereochemistry at C-5 and C-3. Lepadins G (5) and H (6) are epimers at C-2. NMR and molecular modeling studies indicated that the three new compounds adopt a chair-chair conformation in which the nitrogen equatorially substitutes the cyclohexyl ring. This contrasts with lepadins A-C (1-3), which adopt a chair-chair conformation in which the nitrogen axially substitutes the cyclohexyl ring.
authors.affiliation: AstraZeneca R & D Griffith University, Brisbane, Australia.
authors.forename: Rohan A
authors.initials: RA
authors.lastname: Davis
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Carroll
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Quinn
mesh_terms: D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification*; D000818:Animals; D000981:Antiprotozoal Agents / Q000737:chemistry / Q000302:isolation & purification*; D001315:Australia; D002851:Chromatography, High Pressure Liquid; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011804:Quinolines / Q000737:chemistry / Q000302:isolation & purification*; D013237:Stereoisomerism; D014561:Urochordata / Q000737:chemistry*
chemical_list: D000470:Alkaloids; D000981:Antiprotozoal Agents; D011804:Quinolines; C455162:lepadin F; C455163:lepadin G; C455164:lepadin H