A. Tobari et al., Spirostanols obtained by cyclization of pseudosaponin derivatives and comparison of anti-platelet agglutination activities of spirostanol glycosides, EUR J MED C, 35(5), 2000, pp. 511-527
Naturally occurring saponins 3 and 4 have a normal type F ring and alpha-ar
ranged CH3-21 group. Treatments of pseudosaponin peracetates 18 and 19 deri
ved from 3 and 4, respectively, with alcoholic KOH, followed by acidificati
on with acetic acid, gave spirostanols 20 and 22 having iso type F rings as
major products. Structural analyses of sapogenins and saponins derived fro
m pseudo derivatives 11, 12, 18 and 19 were performed by comparisons of the
ir H-1-NMR spectral data and the X-ray analytical data of 3-O-p-bromobenzoy
l sarsasapogenin 7, 3-O-acetyl diosgenin 13 and saponin 20. The mechanisms
of ring-closure reaction of the side chain at C-22 of pseudosapogenins and
pseudosaponins were deduced using stereomodels of the spirostanols derived
from 11 under various reaction conditions. Inhibitory activities of saponin
diglycosides 3, 4, 20, 21 and 25 on human platelet agglutinations induced
by ADP and ristocetin were compared. (C) 2000 Editions scientifiques et med
icales Elsevier SAS.