Chemical Synthesis of Several 2'-O-, 3'-O-Glycosylated Diosgenyl β-D-Glucopyranosides

Abstract

Six T-O-, 3'-O-glycosylated diosgenyl p-D-glucopyranosides (4-9), which have a typical structural pattern of diosgenyl saponins, were synthesized; their synthetic routes are discussed.

Synthesis of novel diosgenyl saponin analogs and evaluation effects of rhamnose moeity on their cytotoxic activity

“…Although both the aglycone and the carbohydrate moieties are required for the exhibition of their antitumor activity, the exact role of the carbohydrate moiety remains unclear. Thus, with target six compounds in hand, the cytotoxicity of the saponins was evaluated [24,[30][31][32][33]. The group of steroidal saponins exhibited a marked structure-dependent growth inhibitory activity against the human hepatocellular carcinoma (HepG2) cells (Table1), which supported that the saccharide group increased the cytotoxicity of trillin, especially for rhamnose.…”

“…High selectivity was observed on the pivaloylation of trillin under pivaloyl chloride (PivCl) in CH2Cl2/pyridine (3:1) solution affording the 3,6-di-Pivprotected diol 7 in 80% yield [23]. Glycosylation of diol 7 with 2,3,4-tri-O-benzoyl-α-L-rhamnopyranosyl trichloroacetimidate 8 [24] (1.2 equiv, -60 ℃) under the promotion of trimethylsilyl trifluoromethanesulfonate (TMSOTf) (0.2 equiv) gave the 2-O-glycosylated product 9 and 2,4-di-O-glycosylated product 10 in 50% and 32% yields, respectively. The presence of an acyl group at the 2-OH position of a sugar donor locks the newly formed glycosidic linkage in the 1,2-trans configuration [24].…”

“…Glycosylation of diol 7 with 2,3,4-tri-O-benzoyl-α-L-rhamnopyranosyl trichloroacetimidate 8 [24] (1.2 equiv, -60 ℃) under the promotion of trimethylsilyl trifluoromethanesulfonate (TMSOTf) (0.2 equiv) gave the 2-O-glycosylated product 9 and 2,4-di-O-glycosylated product 10 in 50% and 32% yields, respectively. The presence of an acyl group at the 2-OH position of a sugar donor locks the newly formed glycosidic linkage in the 1,2-trans configuration [24]. Removal of all the acyl protecting groups of 9 (benzoyl and pivaloyl groups) under NaOH in a solvent mixture of THF/MeOH/H2O (v/v/v= 4:4:1) furnished the naturally existing saponin 1 in 90% yield.…”

Syntheses and anti-cancer activities of glycosylated derivatives of diosgenin

“…Moreover, the carbohydrate subunits attached covalently to the backbone of spirostane saponins play an important role for its bioactivities [18][19][20] . During the previous research in our group, two spirostane saponins(A and B) [21,22] have been isolated from the Chinese medicinal plant Disporopsispernyi Diels (Fig.1) and the results of their anti-cancer activities showed good inhibitory activities against human leukemia cell line HL60(with IC 50 values of 9.3 and 6.1 μmol/L, respectively). These results revealed that the sugar Fig.1 Structures of spirostanic saponins A and B isolated from D. pernyi Diels moieties might be the key pharmacophore for the anti-cancer activities of spirostanic saponins [23] .…”