title: Acetals of three new cycloartane-type saponins from Egyptian collections of Astragalus tomentosus.
abstract: Three new cycloartane-type saponin ethyl acetals, deacetyltomentoside I (2), tomentoside III (3), and tomentoside IV (4), were isolated along with the known acetal tomentoside I (1) from the aerial parts of Astragalus tomentosus of Egyptian origin. The saponins from which the acetals are most probably derived are also new compounds. The structures of the acetals were established as 6alpha-hydroxy-23alpha-ethoxy-16beta,23(R)-epoxy-24,25,26,27-tetranor-9,19-cyclolanosta-3-O-beta-d-xyloside (2), 6alpha-acetoxy-23alpha-ethoxy-16beta,23(R)-epoxy-24,25,26,27-tetranor-9,19-cyclolanosta-3-O-[beta-d-(4'-trans-2-butenoyl)]xyloside (3), and 6alpha-acetoxy-23alpha-ethoxy-16beta,23(R)-epoxy-24,25,26,27-tetranor-9,19-cyclolanosta-3-O-[beta-d-glucopyranosyl(1 --> 2)]-beta-d-xyloside (4), by detailed spectroscopic and chemical studies.
authors.affiliation: Department of Chemistry, M/C 0212, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
authors.forename: Mohamed M
authors.initials: MM
authors.lastname: Radwan
authors.forename: Afgan
authors.initials: A
authors.lastname: Farooq
authors.forename: Nadia A
authors.initials: NA
authors.lastname: El-Sebakhy
authors.forename: Aya M
authors.initials: AM
authors.lastname: Asaad
authors.forename: Soad M
authors.initials: SM
authors.lastname: Toaima
authors.forename: David G I
authors.initials: DG
authors.lastname: Kingston
mesh_terms: D000080:Acetals / Q000737:chemistry / Q000302:isolation & purification*; D027883:Astragalus Plant / Q000737:chemistry*; D004534:Egypt; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010946:Plants, Medicinal / Q000737:chemistry*; D012503:Saponins / Q000737:chemistry / Q000302:isolation & purification*; D013237:Stereoisomerism; D014315:Triterpenes / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D000080:Acetals; D012503:Saponins; D014315:Triterpenes; C485029:deacetyltomentoside I; C485030:tomentoside III; C485031:tomentoside IV; C085352:cycloartane