title: Uniquely modified imidazole alkaloids from a calcareous Leucetta sponge.
abstract: A Fijian collection of the calcareous sponge Leucetta sp. was investigated and yielded four new imidazole alkaloids. One compound, (+)-calcaridine A (6), is unique in its overall structure and consists of a geminally substituted 2-aminoimidazolidinone. An additional compound, (-)-spirocalcaridine A (7), is distinctive in its hexahydrocyclopentamidazol-2-ylidenamine spiro-linked to a cyclohexenone. A third compound, (-)-spirocalcaridine B (8), is the OCH(3) analogue of 7. These compounds have unprecedented skeletons and functionality and are the first nonorganometalic chiral aminoimidazoles isolated from calcareous sponges. The two issues discussed here include the challenges associated with the structure elucidations of 6 and 7 and the relationships to previously encountered Leucetta metabolites.
authors.affiliation: Department of Chemistry and Biochemistry and Institute for Marine Sciences, University of California, Santa Cruz, California 95064, USA.
authors.forename: Ru Angelie
authors.initials: RA
authors.lastname: Edrada
authors.forename: Chad C
authors.initials: CC
authors.lastname: Stessman
authors.forename: Phillip
authors.initials: P
authors.lastname: Crews
mesh_terms: D000470:Alkaloids / Q000737:chemistry* / Q000302:isolation & purification*; D000818:Animals; D005367:Fiji; D007093:Imidazoles / Q000737:chemistry* / Q000302:isolation & purification*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011161:Porifera / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D007093:Imidazoles