title: Perhentidines A-C: macroline-macroline bisindoles from Alstonia and the absolute configuration of perhentinine and macralstonine.
abstract: Three new bisindole alkaloids of the macroline-macroline type, perhentidines A-C (1-3), were isolated from the stem-bark extract of Alstonia macrophylla and Alstonia angustifolia. The structures of these alkaloids were established on the basis of NMR and MS analyses. The absolute configurations of perhentinine (4) and macralstonine (5) were established by X-ray diffraction analyses, which facilitated assignment of the configuration at C-20 in the regioisomeric bisindole alkaloids perhentidines A-C (1-3). A potentially useful method for the determination of the configuration at C-20 based on comparison of the NMR chemical shifts of the bisindoles and their acetate derivatives, in these and related bisindoles with similar constitution and branching of the monomeric units, is also presented.
authors.affiliation: Department of Chemistry,  University of Malaya , 50603 Kuala Lumpur, Malaysia.
authors.forename: Siew-Huah
authors.initials: SH
authors.lastname: Lim
authors.forename: Yun-Yee
authors.initials: YY
authors.lastname: Low
authors.forename: Shin-Jowl
authors.initials: SJ
authors.lastname: Tan
authors.forename: Kuan-Hon
authors.initials: KH
authors.lastname: Lim
authors.forename: Noel F
authors.initials: NF
authors.lastname: Thomas
authors.forename: Toh-Seok
authors.initials: TS
authors.lastname: Kam
mesh_terms: D031051:Alstonia / Q000737:chemistry*; D018360:Crystallography, X-Ray; D026121:Indole Alkaloids / Q000737:chemistry* / Q000302:isolation & purification*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D000078183:Oxindoles; D024301:Plant Bark / Q000737:chemistry
chemical_list: D026121:Indole Alkaloids; D000078183:Oxindoles; C574269:macralstonine; C512190:macroline; C574265:perhentidine A; C574266:perhentidine B; C574267:perhentidine C; C574268:perhentinine