title: Configurational analysis of tetracyclic dimeric pyrrole-imidazole alkaloids using a floating chirality approach.
abstract: The structure elucidation of the palau'amine congener tetrabromostyloguanidine (1), which used interproton distances from ROESY spectra as restraints in a computational approach, the so-called fc-rDG/DDD method, led to a revision of the relative configuration of palau'amine (2) and its congeners in 2007. The recent total synthesis of (±)-palau'amine (2) subsequently confirmed the computed structural revision of the relative configuration. In order to test a broader application range of the fc-rDG/DDD method, the present study investigated two additional dimeric pyrrole-imidazole alkaloids, axinellamine A (3) and 3,7-epi-massadine chloride (4). These calculations allowed the simultaneous assignment of the relative configuration for all eight stereogenic centers of compounds 3 and 4 without using any information from the reported configurations. In contrast to the palau'amine congeners, the fc-rDG/DDD method confirmed the relative configuration originally described for axinellamine A (3) and 3,7-epi-massadine chloride (4).
authors.affiliation: Alfred-Wegener-Institut für Polar- und Meeresforschung in der Helmholtz-Gemeinschaft, Am Handelshafen 12, D-27570 Bremerhaven, Germany. mkoeck@awi.de
authors.forename: Matthias
authors.initials: M
authors.lastname: Köck
authors.forename: Gesine
authors.initials: G
authors.lastname: Schmidt
authors.forename: Ian B
authors.initials: IB
authors.lastname: Seiple
authors.forename: Phil S
authors.initials: PS
authors.lastname: Baran
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry*; D006146:Guanidines / Q000138:chemical synthesis* / Q000737:chemistry*; D007093:Imidazoles / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D006146:Guanidines; D007093:Imidazoles; D011758:Pyrroles; D013141:Spiro Compounds; C520388:axinellamine; C438976:palau'amine