title: A convenient synthesis of C-22 and C-25 stereoisomers of cephalostatin north 1 side chain from spirostan sapogenins.
abstract: A simple transformation of the eight-carbon side chain of a natural spirostan sapogenin into the cephalostatin north 1 spiroketal moiety is described. This methodology, based on an intramolecular hydrogen abstraction reaction promoted by alkoxy radicals, permits the synthesis of C-22 and C-25 stereoisomers of the dioxaspiro[4.4]nonane cephalostatin ring system. The acid-catalyzed isomerization of the spirocenter in the different isomers is studied. [reaction: see text]
authors.affiliation: Instituto de Productos Naturales y Agrobiología del C.S.I.C., Carretera de La Esperanza 3, 38206 La Laguna, Tenerife, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Betancor
authors.forename: Raimundo
authors.initials: R
authors.lastname: Freire
authors.forename: Inés
authors.initials: I
authors.lastname: Pérez-Martín
authors.forename: Thierry
authors.initials: T
authors.lastname: Prangé
authors.forename: Ernesto
authors.initials: E
authors.lastname: Suárez
mesh_terms: D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D010619:Phenazines / Q000138:chemical synthesis*; D010944:Plants / Q000737:chemistry*; D012502:Sapogenins / Q000737:chemistry*; D013141:Spiro Compounds / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013256:Steroids; D013329:Structure-Activity Relationship
chemical_list: D007202:Indicators and Reagents; D010619:Phenazines; D012502:Sapogenins; D013141:Spiro Compounds; D013256:Steroids; C454806:cephalostatin I