title: Structures and solution conformational dynamics of stylissamides G and H from the Bahamian sponge Stylissa caribica.
abstract: Two new peptides, stylissamides G and H, were isolated from extracts of a sample of Stylissa caribica collected in deep waters of the Caribbean Sea. A single sample of S. caribica among a collection of 10 samples that were examined by LC-MS appeared to be a different chemotype from the others in that it lacked the familiar pyrrole-2-aminoimidazole alkaloids, stevensine and oroidin, and contained peptides of the stylissamide class. The structures of the title compounds were solved by integrated analysis of the MS and NMR spectra and chemical degradation. The solution conformation of stylissamide G was briefly examined by electronic circular dichroism and temperature-dependent (1)H NMR chemical shifts of amide NH signals, which supported a conformationally rigid macrocycle.
authors.affiliation: Department of Chemistry and Biochemistry and §Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego , 9500 Gilman Drive, La Jolla, California 92093, United States.
authors.forename: Xiao
authors.initials: X
authors.lastname: Wang
authors.forename: Brandon I
authors.initials: BI
authors.lastname: Morinaka
authors.forename: Tadeusz F
authors.initials: TF
authors.lastname: Molinski
mesh_terms: D000470:Alkaloids / Q000737:chemistry; D000818:Animals; D017691:Caribbean Region; D007093:Imidazoles / Q000737:chemistry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010456:Peptides, Cyclic / Q000737:chemistry* / Q000302:isolation & purification*; D011161:Porifera / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry
chemical_list: D000470:Alkaloids; D007093:Imidazoles; D010456:Peptides, Cyclic; D011758:Pyrroles; C552324:pyrrole-2-aminoimidazole; C000589337:stylissamide G; C000589338:stylissamide H; C077209:oroidin