Synthesis of betavulgaroside III, a representative triterpene seco-glycoside.
Triterpene seco-glycosides constitute a small family of the plant saponins which feature a terminal seco-saccharide appendage deriving supposedly from oxidative scission of a monosaccharide unit. Herein, we have developed synthetic approaches for the first time to the access to these molecules. Betavulgaroside III (1), a representative congener occurring in Beta vulgaris and Achyranthes fauriei, is successfully synthesized in a total of 31 steps with L-arabinose, D-glucose, and oleanolic acid as starting materials. The longest linear sequence requires 23 steps and in an overall 0.9% yield (from D-glucose). The synthesis features oxidative elaboration of the seco-saccharide unit prior to assembly of the triterpene 3,28-bisglycoside. This tactic has been proven superior, in the attempts to the synthesis of the more easily accessible 2''-epi-betavulgaroside III (2), to that employing oxidative cleavage of the terminal saccharide unit at an advanced triterpene 3,28-bisglycoside scaffold.
Key Laboratory of Marine Drugs, Marine Drug and Food Institute, Ocean University of China, Qingdao 266003, China.
Shilei
S
Zhu
Yingxia
Y
Li
Biao
B
Yu
D006027:Glycosides / Q000138:chemical synthesis*; D015394:Molecular Structure; D014315:Triterpenes / Q000138:chemical synthesis*
D006027:Glycosides; D014315:Triterpenes; C531440:betavulgaroside III