title: Xestobergsterol C, a new pentacyclic steroid from the Okinawan marine sponge Ircinia Sp. and absolute stereochemistry of xestobergsterol A.
abstract: A new pentacyclic steroid, xestobergsterol C [1], possessing a cis C/D ring junction, has been isolated together with two known compounds, xestobergsterols A [2] and B [3], from the Okinawan marine sponge Ircinia sp., and the structure determined on the basis of spectral data. Reexamination of the nmr data of xestobergsterols A [2] and B [3] resulted in revision of the configuration at C-23 and of the conformation of ring D in 2 and 3. The absolute stereochemistry of xestobergsterol A [2] was established by the cd exciton chirality method.
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Kobayashi
authors.forename: H
authors.initials: H
authors.lastname: Shinonaga
authors.forename: H
authors.initials: H
authors.lastname: Shigemori
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D002778:Cholestanones / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D002942:Circular Dichroism; D004354:Drug Screening Assays, Antitumor; D007564:Japan; D007939:Leukemia L1210 / Q000188:drug therapy; D009682:Magnetic Resonance Spectroscopy; D051379:Mice; D008968:Molecular Conformation; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D002778:Cholestanones; C093893:xestobergsterol C