Two new 13,14:14,15-disecopregnane-type C21 steroidalglycosides, namely komarosides R (1) and S (2), along with four known compounds (3–6), were obtained from the 95% ethanol extract of the whole herbs of Cynanchum komarovii Al.Iljinski (Asclepiadaceae). The structures of new compounds were elucidated on the basis of 1D, 2D NMR spectroscopic data and acid hydrolysis. Compounds 1 and 2 showed potent
An appraisal of oxoketene cycloaddition methodology for the synthesis of 2,6-dideoxysugars and fluorinated 2,6-dideoxysugars
作者:Christophe Audouard、Kim Bettaney (née Middleton)、Châu T. Doan、Giuseppe Rinaudo、Peter J. Jervis、Jonathan M. Percy
DOI:10.1039/b817672h
日期:——
The cycloaddition reaction of acylketenes with vinyl ethers affords an extremely direct route to 2,6-dideoxysugars and their methyl ethers. The lithiumenolate of commercial 2,6,6-trimethyldioxinone 3 was fluorinated in good yield to afford fluorinated dioxinone 8. An illustrative range of fluorinated 2,6-dideoxysugar derivatives was prepared via the acetyl ketene–vinyl ether cycloadduct. Electronic
Bioactive C<sub>21</sub> Steroidal Glycosides from the Roots of <i>Cynanchum otophyllum</i> That Suppress the Seizure-like Locomotor Activity of Zebrafish Caused by Pentylenetetrazole
Six new C-21 steroidal glycosides, cynotophyllosides A-F (1-6), together with 16 known compounds, were isolated from the roots of Cynanchum otophyllum. The structures of the new compounds were elucidated by spectroscopic analysis and chemical methods. The three major components, otophylloside F (15), otophylloside B (17), and rostratamine 3-O-beta-D-oleandropyranosyl-(1 beta-D-oleandropyranosyl-(1 -> 4)-beta-D-cymaropyranosyl (1 -> 4)-beta-D-cymaropyranoside), suppressed the seizure-like locomotor activity caused by pentylenetetrazole in zebrafish. Preliminary structure-activity relation studies revealed that a pregnene skeleton with a C-12 ester group (ikemaoyl > cinnamoyl > hydroxy > p-hydroxybenzoyl) and a C-3 sugar chain consisting of three 2,6-dideoxysaccharide units is essential for this suppressive activity.