Structural relations and interconversions of isomeric astilbins

Abstract

Reaction of Methyl 2-O-Benzoyl-3-0-methyl-4,6-di-Omethylsulfonyl-/$-D-mannopyranoside (10) with Potassium Benzoate in Refluxing JV,jV-Dimethylformamide (10 hr). An N, N-dimethylformamide solution (10 ml) containing 10 (105 mg, O. 22 mmol) and potassium benzoate (250 mg, 1.56 mmol) was heated at reflux for 10 hr. The precipitate was filtered off and the filtrate was evaporated in vacuo. The residue was chromatographed on silica gel (30 g). Elution with 7:1 benzene-ethyl acetate gave two fractions. The first fraction (23 mg, 20%) was pure 4, whereas the second fraction (75 mg, 65%) was pure 6, the 6:4 ratio being 3.2:1.Methyl 3-O-Methyl-2-0-methylsulfonyl-¡8-D-galactopyranoside (12). To a methanolic solution (10 ml) of 7 (220 mg, 0.44 mmol), metallic sodium (55 mg, 2.30 mmol) was added and the reaction mixture was heated at 60°for 30 min. The solution was neutralized with acetic acid and the solvents were evaporated in vacuo. The residue was chromatographed on A1203 (12 g). Elution with benzene (20 ml), ethyl acetate (20 ml), and 1:1 ethyl acetatemethanol (40 ml) gave pure 12 (125 mg, 98%): mp 164-165°; [a]27D +3°(c 1.12, CHgOH); ir (CHC13) 3500 cm"1 (broad peak, OH); NMR (CDCls) S 3.37 and 3.28 (two s, 6, C-l and C-3 methoxy groups), 3.07 (s, 3, methyl from C-2 methylsulfonyl group).

Simultaneous quantification of five major bioactive flavonoids in Rhizoma Smilacis Glabrae by high-performance liquid chromatography

“…The chemical structures of all the five flavonoids as standards were also confirmed by 1 H NMR and 13 C NMR. The data of ESI-MS, 1 H NMR and 13 C NMR were consistent with those in the literature [25,26].…”

Extractives of the tropical wood wallaba (Eperua falcata Aubl.) as natural anti-swelling agents

“…• Neoengeletin (4)/Neoisoengeletin (5) (8.3/1): 0.22% (Gaffield et al 1975). • Astilbin (6)/Neoastilbin (7) (1.2/1): 0.15% (Gaffield et al 1975;Xu et al 2005).…”

“…• Astilbin (6)/Neoastilbin (7) (1.2/1): 0.15% (Gaffield et al 1975;Xu et al 2005). • p-Hydroxybenzoic acid (8): 0.09%.…”

Screening and identification of potential bioactive constituents in a new herbal prescription seaweed complex preparation

“…Their structures were elucidated using comprehensive spectroscopic methods including 1D and 2D NMR, MS, UV and IR, combined with a variety of chemical methods, and by comparison their data with those reported previously in the literature. The isolated compounds were involved in ten types of chemical structures, including fourteen flavonoid glycosides (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), ten flavonoids (15)(16)(17)(18)(19)(20)(21)(22)(23)(24), four lignans (25)(26)(27)(28), seven phenolic acid compounds (29-34, 42), one steroid (35), one diterpene (36), one monoterpene (37), one phenolic glycoside (38), three iridoid glycosides (39)(40)(41) and one steroid saponin (43) ( Table 1). Among the isolated compounds, about of 50% of them were flavonoid glycosides and flavonoids, and it could be concluded that flavonoid glycosides, flavonoids, phenolic compounds and lignans were the major structure types in the EtOAc and n-BuOH fractions of SCP.…”