Spergularia ramosa

A convergent synthesis of the pentasaccharide derivative 33 of the triterpeniod saponin obtained from the plant Spergularia ramosa was achieved as outlined in Scheme 6 68 The entire assembly relied on use of the trichloroacetimidate protocol and was accomplished in a three plus two fashion. The assembly of the trisaccharide was initiated by the glycosidation of glucosyl trichloroacetimidate donor 22 with rhamnosyl diol acceptor 23 to provide disaccharide 24 in 63% yield. The latter could be used directly as the glycosyl acceptor for the reaction with xylosyl donor 25, leading... 

Scheme 6. Convergent synthesis of the pentasaccharide of Spergularia ramosa,68...

G. Gu and Y. Du, Synthesis of a pentasaccharide derivative corresponding to a triterpenoid saponin isolated from Spergularia ramosa, J. Chem. Soc., Perkin Trans., 1 (2002) 2075-2079. 

---